Kidney sensor, system and use thereof

Abstract

A system for irrigation 6 of the renal system comprises a fluid delivery system 30, a control unit 10 and a pressure sensor 42, the measurements from which the control unit may use to vary operation o

Description

The present invention relates to a sensor, in particular to a sensor for detecting conditions, such as temperature and pressure, within a kidney of a patient, for example during procedures that affect the conditions of pressure and temperature. The present invention further relates to a system employing the sensor, for example a system for the control of an apparatus for treating kidney stones and tumours within the lining of the kidneys. The present invention further relates to a method of detecting conditions within the kidneys of a patient, as well as a method for conducting procedures on the kidneys of a patient, for example the treatment of kidney stones or other minimally invasive endourological procedures. The use of lasers in endourlological procedures is now well established. A recent review of the application of lasers in endourology is provided by Brewin, A.E. and Somani, B.K., ‘What is new in lasers for endourology: looking into the future’, Urology News, Volume 25, No. 2. One important application of lasers is the treatment of kidney stones. Kidney stones are a common condition, with the number of patients developing kidney stones increasing. Urolithiasis, that is the presence of stones in any part of the urinary tract, including the kidneys, ureter, bladder and urethra, is a chronic condition that requires treatment. Techniques for treating kidney stones include shockwave lithotripsy (SWL), ureteroscopy (URS) and percutaneous nephrolithotomy (PCNL). The use of URS and PCNL has increased in recent years, with a decline in the use of SWL and invasive surgery. In the case of URS, an ureteroscope is introduced into the affected region. The ureteroscope is used to visualise the kidney stones and provide a conduit for treatment the stones by means of a laser. During URS, it is common practice to provide irrigation, typically saline irrigation, to expand the ureteral lumen. This permits visualisation of the renal pelvis and calices. In addition, expansion also facilitates the insertion and navigation of the ureteroscope through the renal system. Irrigation to expand the ureteral lumen requires an increase in the fluid pressure within the ureter and the kidneys. Typically, intra-renal pressures range from 10 to 20 cm H2O (0.01 to 0.02 Bar). This pressure is elevated during irrigation and can rise to dangerous levels of from 100 to 300 cm H2O (0.1 to 0.3 Bar). Irrigation may be provided using a number of techniques. Perhaps the simplest is gravity irrigation, where the irrigation fluid is provided to the patient from a reservoir of fluid held at a height above the patient. However, this technique provides little or no control over the irrigation, in particular the increase in fluid delivery or pressure. As a result, gravity irrigation is typically used to apply irrigation fluid at lower pressures, in order to ensure intra-pelvic pressures are kept low and within safe limits. Alternatively, irrigation may be provided by means of a manual pump to provide the irrigation fluid at an elevated pressure. However, it can be difficult to control the increase in intra-pelvic pressure and pressures as high as 250 cm H2O (0.25 Bar) have been recorded. These high pressures result in an increased risk of complications from the procedure, especially bleeding, sepsis and even death. More recently, advanced irrigation systems have been developed, which provide for improved control of the fluid flow and intra-luminal pressures during URS. An example of a commercially available irrigation system is the Thermedx FluidSmart system. Generally, increases in intra-renal fluid pressure up to 20 cm H2O (0.02 Bar) provide a safe working range with a lower risk of complications. Increases in intrarenal pressure above this value significantly increase the risk of post-operative complications. Such complications include bleeding, perirenal collection, sepsis and death. The techniques of conducting URS procedures and the attendant risks are discussed by Neto, A.C.L., et al., ‘Intra-renal pressure and temperature during ureteroscopy: Does it matter?’, IBJU, Vol. 47(2), March - April 2021, pages 436 to 442. During URS, a laser is used to break the kidney stones into smaller fragments, which can be more easily removed and / or may pass out of the body in the urine. The laser treatment releases a significant amount of energy in the form of heat, which in turn raises temperatures within the renal system of the patient, with a risk of damage to the surrounding tissue and organs. The effects of increased temperatures during endourological procedures are discussed by Rice, P., et al., ‘Generated temperatures and thermal laser damage during upper tract endourological procedures using the holmium:yttrium-aluminium-gamet (Ho:YAG) laser: a systematic review of experimental studies’, World Journal of Urology, (2022) 40: pages 1981 to 1992. It is reported that preclinical and clinical studies have shown that temperatures ranging from 41 to 47°C result in a direct cellular destruction. Temperatures exceeding 43°C lead to an exponentially increased cytotoxic effect. The thermal cytotoxic effects are not limited to the peak temperature achieved during laser treatment. As a result, the thermal dose t43 has been defined as the thermal energy required to maintain a temperature of 43°C for 120 minutes. The t43 parameter may be used to identify adverse effects of the laser treatment, with a t43 of greater than 120 minutes giving rise to a high risk of thermal tissue injury. Rice, P., et al. report that irrigation can help to reduce temperatures during URS, with the irrigation fluid acting as a heat sink to remove thermal energy from the site of treatment. Irrigation can help to lengthen the time required to reach the threshold of thermal damage, in turn reducing the treatment time. An examination of data on temperatures produced during laser lithotripsy and suggested strategies for maintaining lower temperatures during endourological procedures is provided by Tokas, T., et al., ‘Temperature change during laser upper-tract endourological procedures: current evidence and future perspective’, Current Opinion Urology, 2022, March, pages 108 to 115. With both pressure and temperature within the renal system of the patient being significant factors during URS, there is a need for improved techniques to carry out URS procedures with a reduced risk of complications arising post-treatment. In particular, there is a need for an improved method and system for carrying out URS procedures which reduce or prevent the occurrence of excessive intra-renal pressures and temperatures. CN 109998698 discloses a numerical control system capable of performing real-time control of renal pelvis pressure in ureteroscopy based on sheath-side optical fibre pressure sensor monitoring. The system employs a double-channel ureter leading-in sheath. A perfusion pump provides a fluid to a kidney through a main channel of the ureter sheath. An optical fibre pressure sensor is placed in a renal pelvis through a side channel of the sheath to monitor the pressure of the renal pelvis. Both channels have suction applied. Based on the measured pressure feedback, the numerical control platform carries out data interaction with an intelligent terminal. The intelligent terminal collects and analyzes the data during the procedure, synchronously optimizing the operation of the system. It is alleged that the system has the advantages of accurate real-time pressure control and can prevent complications, such as kidney injury, serious infection and the like caused by high pressures. CN 211749878 U discloses a manual continuous perfusion device for use in ureteroscopic procedures. The device comprises an infusion pump, a handheld control structure and an infusion device body. The infusion device further comprises a liquid inlet pipe, a liquid outlet pipe, a liquid inlet guide pipe and an infusion extension pipe. More recently, US 2022 / 257108 discloses endoscope devices, systems, and methods for reducing intra-pelvic pressure using same. The endoscope is for insertion into a ureter or an access sheath and comprises a shaft including a first end, a second end positioned axial opposite of the first end, a working channel extending axially through the shaft between the first end and the second end, and at least one protrusion extending from at least one of an exterior surface of the shaft or into the working channel, together with a hand piece releasably coupled to the shaft adjacent the first end. The endoscope device is indicated to overcome problems arising from the limits placed on the size of the endoscope by the diameter of the ureter of the patient. According to a first aspect of the present invention, there is provided a system for irrigation of the renal system of a subject, the system comprising: a fluid delivery system for delivering an irrigation fluid intra-renally to the subject from an irrigation fluid reservoir; and a control system comprising: a pressure sensor for disposing at an intra-renal location within the subject and operable to generate a pressure signal corresponding to the pressure of fluid at the intra-renal location; and a control unit for receiving the pressure signal and controlling the operation of the fluid delivery system to vary the fluid pressure at the intrarenal location. In a further aspect, the present invention provides a method for providing an irrigation fluid to an intra-renal location within a subject during an endourological procedure, the method comprising: providing a flow of the irrigation fluid to the intra-renal location within the subject; sensing the intra-renal fluid pressure within the subject; and controlling the flow of the irrigation fluid in response to the sensed intra-renal fluid pressure. According to a further aspect of the present invention, there is provided a system for operating a laser assembly during an endourological procedure being conducted on a subject, the system comprising: a control system comprising: a temperature sensor for disposing at an intra-renal location within the subject and operable to generate a temperature signal corresponding to the temperature the intra-renal location; and a control unit for receiving the temperature signal and operable to vary the operation of the laser assembly when the temperature at the intra-renal location exceeds a threshold temperature. The present invention further provides a method for controlling the operation of a laser assembly during a laser endourological procedure on a subject, the method comprising: sensing the temperature at an intra-renal location within the subject; comparing the sensed temperature with a threshold temperature; and in the event the sensed temperature exceeds the threshold temperature varying the operation of the laser assembly. In a still further aspect, the present invention provides a system for controlling a laser assembly during an endourological procedure being conducted on a subject, the system comprising: an irrigation system comprising: a fluid delivery system for delivering an irrigation fluid intra-renally to the subject from an irrigation fluid reservoir; and a control system comprising: a temperature sensor for disposing at an intra-renal location within the subject and operable to generate a temperature signal corresponding to the temperature the intra-renal location; a pressure sensor for disposing at an intra-renal location within the subject and operable to generate a pressure signal corresponding to the pressure of fluid at the intra-renal location; and a control unit configured for: receiving the temperature signal and operable to vary the operation of the laser assembly when the temperature at the intrarenal location exceeds a threshold temperature; and receiving the pressure signal and controlling the operation of the fluid delivery system to vary the fluid pressure at the intra-renal location. The present invention further provides a method for controlling the operation of a laser assembly during a laser endourological procedure on a subject, the method comprising: providing a flow of the irrigation fluid to the intra-renal location within the subject; sensing the temperature at an intra-renal location within the subject; sensing the intra-renal fluid pressure within the subject; and controlling the flow of the irrigation fluid in response to the sensed intra-renal fluid pressure; comparing the sensed temperature with a threshold temperature; and in the event the sensed temperature exceeds the threshold temperature varying the operation of the laser assembly. The present invention employs a control system comprising one or more sensors. The one or more sensors are each suitable for being deployed in vivo. In use, the one or more sensors are disposed at an intra-renal location, that is a location within the renal system of the subject. In this respect, references to the ‘renal system’ of the subject and to an ‘intra-renal location’ are references to the system comprised of the kidneys, ureters, bladder, and the urethra, and to a location therewithin. The sensors provide signals relating to parameters within the renal system of the subject, in particular fluid pressure and temperature, to a control unit, which then operates to control the operation of the various components of the system, as described in more detail below. The systems and methods of the present invention provide a significant advantage when conducting endourological procedures, especially those involving a laser assembly, such as laser lithotripsy for treating kidney stones. In particular, the present invention allows for improved control during the procedure, reducing the occurrence of conditions within the renal system of the subject that can result in damage to tissue and / or organs and the complications arising from the procedure, as discussed and highlighted in the prior art documents referred to above. In one embodiment, the present invention employs an irrigation system for providing an irrigation fluid intra-renally to the subject from an irrigation fluid reservoir. Irrigation of the renal system of the subject during an endourological procedure is common practice. As described hereinbefore, irrigation of the urinary collection system acts to enlarge the passages of the system, improving access to the system and facilitating the visualisation and detection of conditions, such as kidney stones. In addition, as also described hereinbefore, when the procedure involves the generation of heat within the renal system of the subject, such as the use of a laser assembly, for example during laser lithotripsy, the irrigation fluid acts as a heat sink, removing heat energy from the treatment site, in turn reducing the temperature at the treatment site and reducing or eliminating damage to tissue as a result of excessive temperatures. The irrigation system provides a flow of irrigation fluid to the urinary collection system of the subject from a fluid reservoir. This may be achieved using gravity from a reservoir, such as a bottle or bag, held at an elevated position above the subject. More preferably, the irrigation system employed in the present invention comprises a pump. The irrigation fluid is delivered by the pump to locations within the renal system of the subject. The irrigation fluid is delivered by a tube through the urethra and into the ureter and other locations within the urinary collection system of the subject. The action of the irrigation fluid is to expand the various passages within the urinary collection system, facilitating the insertion and location of components, such as an ureteroscope or a fibre for transmitting light from a laser assembly. In addition, the expansion of the various passages under the action of the pressure of the irrigation fluid improves the visualisation within the urinary collection system, in turn allowing the surgeon improved visibility of the system and any artifacts therein, such as kidney stones. Still further, in procedures where heat is generated, such as the laser treatment of kidney stones (laser lithotripsy), the irrigation fluid acts as a heat sink, removing heat energy from the location and helping to reduce collateral damage to the tissue and organs around the treatment site. The irrigation fluid may be any suitable fluid. Most typically, the irrigation fluid is a saline solution. The present invention preferably employs a pump to deliver the irrigation fluid under pressure from a fluid reservoir to the urinary collection system of the subject. This is in contrast to the conventional techniques for irrigation of the urinary collection system, which rely on the fluid being fed to the subject under the action of gravity from a reservoir, typically a saline bag or bottle. The pump delivers irrigation fluid to a location within the urinary collection system of the subject. The location of the irrigation fluid delivery may the same location as that of the one or more sensors. Any suitable fluid pump may be employed and suitable pumps are known in the art and are commercially available. One preferred form of pump is a peristaltic pump. The operation of the fluid delivery system is controlled by the control unit, as described in more detail below. The fluid delivery system delivers the irrigation fluid to the urinary collection system of the subject through a suitable conduit. Suitable conduits, such as tubes and catheters are known in the art and are commercially available. Preferably, the irrigation system further comprises a fail-safe system. In use, the fail-safe system may be operated in the event there is a problem with the operation of the irrigation system and stops the flow of irrigation fluid to the subject. The fail-safe system preferably comprises an on / off valve disposed on the outlet side of the fluid delivery system. In the event of a problem occurring in the irrigation system, for example a failure of the fluid delivery system or its control, the on / off valve of the fail-safe system may be closed to prevent an excessive fluid pressure occurring within the urinary collection system of the subject. In particular, the on / off valve may be shut in the event of an excessive fluid pressure occurring in the irrigation system. For example, the control unit may be configured to close the on / off valve in the event of a high irrigation fluid pressure occurring which cannot be quickly reduced by adjusting the operation of the fluid delivery system, such as a failure of the pump to shutdown when commanded. The fail-safe system may comprise an override to allow the user, such as a surgeon, to shut the on / off valve and rapidly stop the flow of irrigation fluid to the subject. The normal state of the on / off valve is preferably closed. In the event of a power failure occurring, the valve returns to its normal state, preventing the flow of irrigation fluid to the subject. Preferably the irrigation system comprises a conduit for returning irrigation fluid out of the urinary collection system of the subject. Again, suitable conduits, such as tubes and catheters are known in the art. In one embodiment, the present invention employs a laser assembly. Suitable laser assemblies for use in conducting endourological procedures are well known and understood in the art and are commercially available. Suitable lasers are discussed, for example, in the prior art documents acknowledged above. Rice, P., et al., ‘A Systematic Review of Thulium Fiber Laser: Applications and Advantages of Laser Technology in the Field of Urology’, Research and Reports in Urology, 2021, No. 13, pages 519 to 527, also provides a discussion of laser assemblies for use in endourological procedures. One example of a suitable laser assembly is a holmium:yttrium-aluminium-gamet (Ho:YAG) laser. The present invention employs a control system. In use during an endourological procedure, the control system controls the operation of apparatus being used during the procedure, for example the operation of the irrigation system and / or the operation of a laser assembly. The control system comprises one or more sensors. The one or more sensors are each suitable for being deployed in vivo. In use, as noted hereinbefore, the one or more sensors are disposed at an intra-renal location, that is a location within the renal system of the subject, more particularly at a location in the urinary collection system of the subject. The intra-renal location for the or each sensor may be any location within the urinary collecting system of the renal system of the subject that may be accessed through the urethra, the bladder and the ureter and includes the ureter, the kidney pelvis and vessels within the kidney accessible from the renal pelvis, such as the major calyx and the minor calyx. A particularly advantageous application of the present invention is the treatment of kidney stones, more particularly using a laser assembly. Kidney stones typically occur on the interior surfaces of the kidney where urine leaves the kidney tissue and enters the urinary collection system. The intra-renal location for the one or more sensors may be any of the locations where kidney stones occur within the subject, including any part of the urinary collection system, such as the ureter, the renal pelvis, the major calyx and the minor calyx. The size of the sensor will determine the locations within the urinary system of the subject that can be accessed and used in the present invention. One preferred location for the one or more sensors is within the renal pelvis of the urinary collection system within the kidney, with location of the sensor within an individual calyx being less common. Each sensor is therefore preferably of a size to allow it to be inserted and located within the renal pelvis. Each sensor may be sized for location into an individual calyx within the kidney, if treatment at this location is required. Preferably, the sensor has a width or diameter that is less than 2 mm, more preferably less than 1.5 mm, still more preferably less than 1 mm. It is particularly preferred that the sensor has a width or diameter that is less than 0.75 mm, preferably less than 0.5 mm, more preferably less than 0.4 mm, still more preferably less than 0.3 mm, more preferably still less than 0.25 mm. In this respect, the ‘width’ or ‘diameter’ of the sensor is the dimension of the sensor that extends laterally across the sensor in the orientation in which the sensor is to be introduced and moved along the passages of the urinary collection system of the subject, such as the ureter, the major calyx and the minor calyx. The sensor is preferably housed within a tube. This provides a number of advantages. First, the use of the tube facilitates introducing the sensor into the urinary collection system of the subject to the required location. Second, the tube acts to protect the sensor, which may otherwise be vulnerable to damage during the procedures being carried out. The sensor is disposed completely or substantially completely within the tube at or adjacent the open end of the tube, where the sensor is exposed to the fluid and environment at the location within the urinary collection system of the subject. Preferably, the sensor extends no further than the end of the tube. In one preferred embodiment, the sensor extends within the tube to the end of the tube, preferably substantially flush with the open end of the tube. In an alternative embodiment, the sensor extends to the end portion of the tube and is spaced from the open end of the tube. The tube is preferably coloured, more preferably a colour other than red, to allow for identification of the tube and its properties, for example one or more of the sensor it contains and the size of the tube and sensor. The tube is of a size to accommodate the sensor. In one preferred embodiment, the tube is a 6 French tube (2 mm outer diameter) or smaller, more preferably a 5 French tube (1.667 mm outer diameter) or smaller, still more preferably a 4 French tube (1.333 mm outer diameter) or smaller, more preferably still a 3 French tube (1 mm outer diameter) or smaller. In one preferred embodiment, the sensor has a width of about 250 microns and is housed within a 3 French tube (1 mm outer diameter, 0.5 mm inner diameter). In one embodiment, the sensor is operable to sense one of the fluid pressure or the temperature at the location within the renal system of the subject. In this embodiment, when both fluid pressure and temperature are to be sensed, the present invention employs one or more pressure sensors and one or more temperature sensors. In one embodiment the sensor is operable to sense both fluid pressure and temperature at the location within the renal system of the subject. One or a plurality of pressure / temperature sensors may be employed. Alternatively, one or more combined pressure / temperature sensors may be employed together with one or more fluid pressure sensors and / or one or more temperature sensors. In this way, the system may be provided with redundancy, to accommodate the failure or improper operation of one sensor. In embodiments where a plurality of sensors is employed, the sensors may be deployed at the same location within the urinary collection system of the subject or at two or more different locations. In one preferred embodiment, the sensor or sensors detecting both pressure and temperature are deployed at the same location. In embodiments in which heat is being released during the procedure, for example with procedures employing a laser assembly, such as laser lithotripsy, it is particularly preferred that the or each temperature sensor is deployed at a location close to or adjacent the treatment site. In this way, the temperature of the fluid surrounding the treatment site may be measured, in turn providing an indication when excessive temperatures are being reached which may result in damage to the surrounding tissue. Suitable technology for the one or more sensors used in the present invention is known in the art. In one preferred embodiment, Micro Electro Mechanical Systems (MEMS) sensors are employed. These sensors offer the advantage of having a small size that can be accommodated at the preferred locations within the urinary collection system of the subject and also have a low power consumption. Suitable sensors are known in the art and are commercially available, for example the SMI Intrasense range of sensors available from TE Connectivity. The SMI Intrasense sensors rely on MEMS technology and can be configured to sense both pressure and temperature. Suitable temperature sensors are also available from Okazaki Manufacturing Company. In one preferred embodiment, the urinary collection system of the subject is irrigated and the irrigation fluid is returned via a suitable conduit, as described hereinbefore. Preferably, the pressure of the irrigation fluid returning from the urinary collection system of the subject is measured. Suitable pressure sensors for measuring the pressure of the returned irrigation fluid are known in the art and are commercially available. In one preferred embodiment, the urinary collection system of the subject is irrigated and the irrigation fluid is returned via a suitable conduit, as described hereinbefore. Preferably, the temperature of the irrigation fluid returning from the urinary collection system of the subject is measured. Suitable temperature sensors for measuring the temperature of the returned irrigation fluid are known in the art and are commercially available. The temperature of the irrigation fluid leaving the subject may be used by the control unit to compare with the temperature sensed inside the urinary collection system. In general, the temperature of the fluid leaving the subject is expected be lower that the fluid temperature within the urinary collection system, in particular close to or at the site of treatment with the laser. In addition, during the early stages of laser treatment, for example for kidney stone removal, the access of the irrigation fluid up to the kidney may be restricted, so that the majority of the fluid being provided to the urinary collection system may not reach the treatment site to start with, but may still be heated by the action of the laser. The difference between the fluid exit temperature and the temperature within the urinary collection system closer to the treatment site may give an indication of a blockage preventing the proper flow of the irrigation fluid, for example. Such a blockage may require the pressure of the irrigation fluid from the fluid delivery system to be adjusted, for example increased in order to provide more irrigation fluid to the treatment location, or decreased, depending on the requirements of the user. This feature enables the user to have more control over the flow of the irrigation fluid within the urinary collection system. In one preferred embodiment, the system further comprises a sensor for measuring the prevailing ambient or atmospheric pressure. Again, suitable sensors for measuring the prevailing ambient pressure are known in the art and are commercially available. By sensing the prevailing atmospheric pressure, the system may provide the user with an indication of both the absolute pressure of the irrigation fluid and the relative pressure of the irrigation fluid. The user is preferable able to select either one or both of the pressure values to be indicated by the control system, for example on a visual display. The control system of the present invention further comprises a control unit. The control unit performs a number of different functions, depending upon the embodiment of the system. The control unit is operable to receive signals from the one or more sensors of the system. In particular, the control unit is configured to receive signals relating to the pressure and / or temperature sensed by the or each sensor at the in vivo location within the urinary collection system of the subject. The control unit receives signals from the sensors by way of a suitable interface. Suitable interfaces are known in the art and include, serial data interfaces, such as I2E serial data interfaces, and direct wire connections. In one embodiment, the control unit receives a signal from the or each pressure sensor at the in vivo location or locations. Data relating to the pressure sensed at the in vivo location is used by the control unit to control the supply of irrigation fluid to the urinary collection system of the subject. The control unit is configured to control the pressure of the irrigation fluid being supplied to the urinary collection system of the subject during the procedure. For example, the control unit may be configured to control the operation of the fluid delivery system to vary the pressure of the fluid being output by the fluid delivery system. Alternatively or in addition, the control unit may be configured to operate one or more valves on the output side of the fluid delivery system to regulate the pressure of the irrigation fluid being supplied to the urinary collection system of the subject. As discussed above, when the urinary collection system is being irrigated during an endourological procedure, it is important to avoid excessive fluid pressures within the urinary collection system. As indicated hereinbefore, pressures of 40 cm of H2O or above can increase post-operative complications, with an increased risk of the subject experiencing bleeding, perirenal collection and sepsis. In one embodiment, the control unit is provided with a threshold pressure for the irrigation fluid, that is the maximum acceptable pressure of irrigation fluid at the in vivo location within the urinary collection system of the subject. The threshold pressure may be preset within the control unit. Alternatively, or in addition, the threshold pressure may be manually input into the control unit by a user via a user interface. In the event the pressure sensed by the sensor at the location in the urinary collection system exceeds the threshold pressure provided in the control unit, the control unit operates to reduce the pressure of irrigation fluid being provided to the subject. The control unit may act to reduce the pressure of the irrigation fluid immediately, in situations where a pressure exceeding the threshold pressure has been sensed by the sensor. Alternatively, the control unit may be configured to act to reduce the pressure of the irrigation fluid only after a period of time has elapsed. The period of time before the control unit acts to reduce the irrigation fluid pressure may be preset within the control unit and / or may be manually input into the control unit by a user via a user interface. As noted above, in the event a fluid pressure exceeding the threshold pressure is sensed, the control unit acts to reduce the pressure of the irrigation fluid being supplied to the subject. For example, the control unit may act to reduce the output pressure of the fluid delivery system. The control unit may be configured to increase the output pressure of the fluid delivery system once the pressure of the irrigation fluid sensed at the in vivo location within the urinary collection system of the subject has fallen to or below an acceptable operating pressure. Alternatively or in addition, the control unit may switch off the fluid delivery system, in order to stop the supply of irrigation fluid to the urinary collection system of the subject, for example in the event of a rapid surge in the pressure of the irrigation fluid sensed by the sensor within the urinary collection system of the subject. The control unit may be configured to restart the fluid delivery system once the sensed fluid pressure has returned to an acceptable operating level. The control unit may be configured to require a user to input a command via a user interface to restart the fluid delivery system. The control unit may be configured to allow the operation of the fluid delivery system to resume or return to normal operation once the pressure sensed within the urinary collection system of the subject has fallen below the threshold pressure. This may occur immediately upon the pressure falling below the threshold pressure or after a period of time has elapsed. The period of time before the control unit allows operation of the fluid delivery system to resume or the output pressure increased may be preset within the control unit and / or may be manually input into the control unit by a user via a user interface. Alternatively, the control unit may be provided with a lower threshold pressure, below the threshold pressure, with operation of the fluid delivery system only being resumed once the sensed pressure has fallen below the lower threshold pressure. Again, this may occur immediately upon the sensed pressure falling below the threshold pressure or after a period of time has elapsed. The period of time before the control unit allows operation of the fluid delivery system to resume may be preset within the control unit and / or may be manually input into the control unit by a user via a user interface. In one embodiment, the system comprises a manual override. The override is operated by the user, for example a surgeon conducting the procedure. The override requires the user to manually intervene in the operation of the control unit. The override may be operated in any suitable way by the user, for example be foot-operated and / or hand-operated. The override allows the user to counter the action of the control unit to reduce the pressure or stop the flow of irrigation fluid to the subject. If, in the opinion of the user, it is appropriate for irrigation to continue, the override may be operated and irrigation continued. The control unit may be configured to limit the number of times the override may be employed during a given time period or during the entire procedure and / or to limit the length of time that the override can be effected, before the control unit acts to reduce the pressure of the irrigation fluid being supplied to the subject or stop the fluid supply, for example by switching off the pump. The control unit may also be configured to prevent the override being implemented in event an excessively high pressure is sensed within the urinary collection system of the subject. In this respect, the control unit may be provided with a preset excessively high pressure threshold, preferably pre-programmed into the control unit, such that when the sensed fluid pressure exceeds this threshold pressure, the control unit prevents the override being implemented. In one embodiment, the control unit receives a signal from the or each temperature sensor at the in vivo location or locations. Data relating to the temperature sensed at the in vivo location is used by the control unit to control the release of heat energy within the urinary collection system of the subject during the procedure, especially by the action of a laser during an endourological procedure employing a laser assembly, such as laser lithotripsy. The control unit is configured to control the operation of the laser assembly during the procedure. As discussed above, when an endourological procedure involving the use of a laser is being conducted, such as laser lithotripsy, it is important to avoid excessive temperatures arising within the urinary collection system. As indicated hereinbefore, temperatures in excess of 43°C present an increased risk of tissue being damaged. Temperatures in the range of from 40 to 60°C can promote tissue damage and cellular death. During a laser endourological procedure, control of the operation of the laser assembly and control of irrigation, if being employed, allow the in vivo temperature to be controlled In one embodiment, the control unit is provided with a threshold temperature for the in vivo location within the urinary collection system of the subject where the laser beam is being applied, that is the maximum acceptable temperature of the tissue and surrounding fluid at the location. The threshold temperature may be preset within the control unit. Alternatively, or in addition, the threshold temperature may be manually input into the control unit by a user via a user interface. In the event the temperature sensed by the sensor at the location in the urinary collection system exceeds the threshold temperature provided in the control unit, the control unit operates to reduce the temperature. The control unit may act to reduce the temperature immediately a temperature exceeding the threshold temperature has been sensed within the urinary collection system of the subject. Alternatively, the control unit may be configured to act to reduce the temperature only after a period of time has elapsed. The period of time before the control unit acts to reduce the temperature may be preset within the control unit and / or may be manually input into the control unit by a user via a user interface. In the event that the threshold temperature is exceeded, the control unit is configured to reduce the temperature. In particular, the control unit is configured to vary the operation of the laser assembly. More particularly, in the event the threshold temperature at a location within the urinary collection system of the subject is exceeded, the control unit is configured to reduce the power output of the laser assembly, in turn reducing the heat energy released at the intra-renal location. In one embodiment, the control unit may allow the laser assembly to continue operating, but reduce the power output of the laser assembly. Alternatively, or in addition, the control unit may be configured to switch off the laser assembly, for example by interrupting the power supply to the laser assembly and / or initiating the shut-down procedure for the laser assembly. The control unit may switch off the laser assembly, for example, in the event of a rapid increase in temperature above the threshold temperature being sensed. The control unit may be configured to allow the operation of the laser assembly to resume once the temperature sensed within the urinary collection system of the subject has fallen below the threshold temperature. This may occur immediately upon the temperature falling below the threshold temperature or after a period of time has elapsed. The period of time before the control unit allows operation of the laser assembly to resume may be preset within the control unit and / or may be manually input into the control unit by a user via a user interface. Alternatively, the control unit may be provided with a lower threshold temperature, below the threshold temperature, with operation of the laser assembly only being resumed once the sensed temperature has fallen below the lower threshold temperature. Again, this may occur immediately upon the temperature falling below the threshold temperature or after a period of time has elapsed. The period of time before the control unit allows operation of the laser assembly to resume may be preset within the control unit and / or may be manually input into the control unit by a user via a user interface. As noted above, in one embodiment, the control unit operates to interrupt the power supply to the laser assembly and stop the laser assembly operating. This mode of operating has the advantage that the system of the present invention may be employed with an existing laser assembly without any modification of the assembly being required. Rather, it is only necessary to provide a switch in the power supply to the laser assembly, which switch is operable by the control unit. In one embodiment, the system comprises a manual override. The override is operated by the user, for example a surgeon conducting the procedure. The override may be operated in any suitable way by the user, for example be foot-operated and / or hand-operated. The override allows the user to counter the action of the control unit to reduce the power output or stop operation of the laser assembly. If, in the opinion of the user, it is appropriate for laser treatment to continue, the override may be operated and the operation of the laser assembly continued. The control unit may be configured to limit the number of times the override may be employed during a given time period or during the entire procedure and / or to limit the length of time that the override can be effected, before the control unit acts to reduce the power output of the laser assembly or halt the operation of the laser assembly. The control unit may also be configured to prevent the override being implemented in event an excessively high temperature is sensed within the urinary collection system of the subject. In this respect, the control unit may be provided with a preset excessively high temperature threshold, preferably pre-programmed into the control unit, such that when the sensed fluid temperature exceeds this threshold temperature, the control unit prevents the override being implemented. As noted hereinbefore, irrigation fluid provided to the urinary collection system of the subject acts as a heat sink and removes heat energy from the surrounding tissue, in turn reducing the temperature. As a result, the irrigation fluid, if being employed, may be used to control the temperature within the urinary collection system. For example, upon an increase in temperature being sensed, the control unit may act to increase the flowrate of irrigation fluid provided to the subject by the fluid delivery system. Preferably, any action by the control unit to regulate the temperature within the urinary collection system is governed by the fluid pressure being sensed by the pressure sensor at the in vivo location. If the system comprises a manual override to counter the action of the control unit to reduce the fluid pressure, as described above, this may be used to maintain a high fluid flowrate, with the object of quickly reducing the temperature at the in vivo location. In one embodiment, the control unit receives signals relating to the pressure and / or temperature of the irrigation fluid leaving the subject. As discussed above, data relating to the pressure and / or temperature of the irrigation fluid leaving the subject may be used by the control unit for a number of different reasons. For example, the data may indicate a blockage preventing the irrigation fluid from reaching the sensors at the treatment location within the urinary collection system of the subject. When the control unit detects a blockage in this manner, the control unit preferably provides an audible and / or visual warning to the user that a blockage has been detected. As also discussed hereinbefore, the control unit may receive a signal with data relating to the prevailing ambient air pressure. This allows the control unit to calculate the pressure of the irrigation fluid within the urinary collection system of the subject in absolute terms, as well as relative terms. The control unit may therefore display to the user irrigation fluid pressure readings in either one or both absolute pressure and relative pressure. As also discussed hereinbefore, the irrigation fluid system may comprise a fail-safe comprising an on / off valve, allowing the flow of irrigation fluid from the fluid delivery system to the subject to be shut off. The control unit may be configured to active the on / off valve to close the valve in the case of an emergency, such as when the control of the flow and pressure of the irrigation fluid by other means, for example through adjusting the operation of the fluid delivery system, is lost. As also noted above, the system may comprise a manual override, allowing the user to close the on / off valve in the event of an emergency, for example failure of the control unit. As mentioned hereinbefore, the control unit may be provided with a user interface. Any suitable interface may be employed. Preferably, the user interface provides a visual display and / or an audio display to allow the user to monitor and control the operation of the system. Preferably, the user interface is an audio / visual interface, for example comprising a touch screen. As described hereinbefore, the control unit may be provided with a threshold pressure, that is the maximum pressure of the irrigation fluid permitted to be sensed by the sensors at the in vivo location before the control unit acts to reduce the pressure of the irrigation fluid. The threshold pressure may be pre-programmed into the control unit. Alternatively, or in addition, the user may be allowed to input a threshold pressure into the control unit via the user interface. In the case that the control has a pre-programmed threshold pressure, the threshold pressure input by the user may override the pre-programmed value. The control unit may be configured to only permit the user to input threshold pressures within a pre-specified range, representing an acceptable range of irrigation fluid pressures. As described hereinbefore, the control unit may be provided with a lower threshold pressure, that is the pressure of the irrigation fluid permitted to be sensed by the sensors at the in vivo location before the control unit acts to resume the supply of irrigation fluid to the subject. The lower threshold pressure may be preprogrammed into the control unit. Alternatively, or in addition, the user may be allowed to input a lower threshold pressure into the control unit via the user interface. In the case that the control has a pre-programmed lower threshold pressure, the lower threshold pressure input by the user may override the preprogrammed value. The control unit may be configured to only permit the user to input lower threshold pressures within a pre-specified range, representing an acceptable range of irrigation fluid pressures. As described hereinbefore, the control unit may be provided with a threshold temperature, that is the maximum temperature permitted to be sensed by the sensors at the in vivo location before the control unit acts to reduce the temperature, for example by adjusting or stopping the operation of the laser assembly. The threshold temperature may be pre-programmed into the control unit. Alternatively, or in addition, the user may be allowed to input a threshold temperature into the control unit via the user interface. In the case that the control has a pre-programmed threshold temperature, the threshold temperature input by the user may override the pre-programmed value. The control unit may be configured to only permit the user to input threshold temperatures within a prespecified range, representing an acceptable range of temperatures for the procedure. As described hereinbefore, the control unit may be provided with a lower threshold temperature, that is the temperature permitted to be sensed by the sensors at the in vivo location before the control unit acts to resume the normal operation of the laser assembly. The lower threshold temperature may be preprogrammed into the control unit. Alternatively, or in addition, the user may be allowed to input a lower threshold temperature into the control unit via the user interface. In the case that the control has a pre-programmed lower threshold temperature, the lower threshold temperature input by the user may override the pre-programmed value. The control unit may be configured to only permit the user to input lower threshold temperatures within a pre-specified range. As described hereinbefore described, in one embodiment, the system comprises an override allowing the user to override the action of the control unit to adjust the operation of the irrigation system and / or the laser assembly. The override may be operated via the user interface, for example by having the user input commands to the control unit via a touchscreen. Alternatively, or in addition, the override may comprise a foot control and / or a hand control, allowing the user to activate the override using their foot and / or their hand. In one embodiment, the control unit provides an indication of the operating parameters of the system via the user interface. Preferably, the control unit provides an indication of one or both of the pressure and temperature sensed at the in vivo location. For example, the control unit may provide a continuous visual display over the pressure and temperature being sensed. The continuous visual display may be one or both of graphical and numerical. The continuous visual display may be accompanied by an audible signal indicating the sensed pressure and / or sensed temperature. Preferably, the control unit provides via the user interface a visual warning signal and / or an audible warning signal when a threshold value of pressure and / or temperature is exceeded. Preferably, the control unit is configured to provide both a visual and an audible warning signal when a threshold value of pressure and / or temperature is exceeded. In addition, the control unit may be configured to alert the user when a sensed value of pressure and / or temperature is approaching a threshold value. In one embodiment, the control unit is configured to transmit data relating to the procedure being undertaken to a patient record system. The control unit may communicate with the patient record system by a wired connection. Alternatively, the control unit may communicate with the patient record system wirelessly. Suitable wireless communication protocols are known in the art. In one embodiment, the control unit comprises a data storage device, for example a memory, with data relating to the procedure being stored by the control unit during the procedure. Data from the data storage device may be retrieved during the procedure and / or after the procedure has been completed, as may be required. As described hereinbefore, the system and method of the present invention are particularly advantageous when employed to conduct an endourological procedure employing a laser assembly, especially a laser lithotripsy procedure to treat kidney stones, in a subject. Accordingly, in a still further aspect, the present invention provides a system for conducting an endourological procedure employing a laser assembly, more especially a laser lithotripsy procedure on a subject, the system comprising: a laser assembly for generating a laser beam for deploying at an in vivo location within the endourological system of the subject; a temperature sensor for disposing at an intra-renal location within the subject and operable to generate a temperature signal corresponding to the temperature the intra-renal location; an irrigation system comprising: a pressure sensor for disposing at an intra-renal location within the subject and operable to generate a pressure signal corresponding to the pressure of fluid at the intra-renal location; and a fluid delivery system for delivering an irrigation fluid intra-renally to the subject from an irrigation fluid reservoir; and a control unit configured for: receiving the temperature signal and operable to interrupt the operation of the laser assembly when the temperature at the intrarenal location exceeds a threshold temperature; and receiving the pressure signal and controlling the operation of the fluid delivery system to vary the fluid pressure at the intra-renal location. The present invention further provides a method for conducting a laser endourological procedure on a subject, more especially a laser lithotripsy procedure, the method comprising: providing a flow of the irrigation fluid to the intra-renal location within the subject; sensing the temperature at an intra-renal location within the subject; sensing the intra-renal fluid pressure within the subject; and controlling the flow of the irrigation fluid in response to the sensed intra-renal fluid pressure; comparing the sensed temperature with a threshold temperature; and in the event the sensed temperature exceeds the threshold temperature varying the operation of the laser assembly. According to a further aspect of the present invention, there is provided a sensor assembly for disposing at an intra-renal location within a subject, the sensor assembly comprising: a tube having an open end, in use the tube extending into the renal system of the subject with the open end disposed at the intra-renal location; a sensor for detecting the fluid pressure and / or temperature at the intra-renal location, wherein the sensor is disposed in the end portion of the tube, the sensor having a distal end disposed at the open end of the tube or disposed within the tube a distance from the open end, whereby in use the sensor is exposed to fluid from the renal system entering the open end of the tube; and at least one lead extending from the sensor in a proximal direction along the tube. Details and embodiments of the sensor assembly are as hereinbefore described. Embodiments of the present invention will now be described, by way of example only, having reference to the accompanying drawings, in which: Figure 1 is a diagrammatical representation of a system for conducting a laser lithotripsy on a subject according to one embodiment of the present invention; Figure 2 is diagrammatical representation of the components of the system of Figure 1; Figure 3 is a cross-sectional view of one embodiment of a sensor assembly of the present invention; and Figure 4 is a diagrammatical view of one half of the renal system of the subject with a sensor assembly of the present invention in location. Turning first to Figure 1, there is shown a representation of a subject 2 undergoing an endourological procedure, in particular laser lithotripsy for the treatment of kidney stones. The laser lithotripsy is being conducted using one embodiment of a system comprising a laser assembly 4, such as a holmium:yttrium-aluminium-garnet (Ho:YAG) laser assembly, as known in the art. The beam generated by the laser assembly 4 is directed into the urinary collection system of the subject 2 via a ureteroscope 4a. The subject 2 is provided with saline irrigation of the urinary collection system by an irrigation system 6 through a feed line 6a and a return line 6b. The procedure is controlled using a control system, generally indicated as 8. The control system 8 comprises a control unit 10, which controls the operation of the laser assembly 4 and the irrigation system 6, while also providing a user interface 12. The control unit 10 receives signals from one or more sensors disposed within the urinary collection system of the subject 2 by a lead 10a via an I2E serial interface. The control unit 10 communicates with a remote patient records system 14 by wireless communication 16. Turning to Figure 2, details of the components and their configuration within the system are shown. The irrigation system 6 comprises a peristaltic pump 30 receiving an irrigation fluid, such as a saline solution, from a reservoir 32, such as a bottle or bag, via a line 34. Pressurised irrigation fluid is provided by the pump 30 via the feed line 6a to the subject 2. A control valve 36 is present in the feed line 6a, the operation of which is controlled by the control unit 10 by means of a signal line 38. Operation of the pump 30 is controlled by the control unit 10 via a signal line 40. A manual override 70 is provided to allow the control valve 36 to be closed by a user in the event of an emergency, for example when an excessively high irrigation fluid pressure within the urinary system of the subject is detected and the normal functions of the control system to reduce the pressure have failed. As described above with reference to Figure 1, the irrigation system includes a return line 6b, through which irrigation fluid is returned from the urinary collection system of the subject 2. As shown in Figure 2, a pressure sensor 42 and a temperature sensor 44 are provided in the return line 6b to sense the pressure and temperature respectively of the returning irrigation fluid. Signals with data relating to the sensed pressure and temperature are provided to the control unit 10 by signal lines 46 and 48. A pressure sensor 72 is provided to sense the prevailing ambient air pressure and provide a signal with data relating to the sensed ambient pressure to the control unit 10 via a signal line 74. As described above with reference to Figure 1, the system comprises a laser assembly 4, operable to deliver a laser beam to the urinary collection system of the subject 2 through an ureteroscope 4a. The operation of the laser is controlled by the control unit by means of a signal line 50. Electrical power is supplied to the laser assembly 4 via a cable 52. A cutoff switch 54 is provided in the cable 52, operated by the control unit 10 via a signal line 56. An override is provided to allow a user to override the action of the control unit 10 to operate the cut-off switch 54 and switch off the power supply to the laser assembly 4. In the embodiment shown in Figure 2, the override comprises a foot-operated override unit 58. The system may alternatively or in addition comprise a hand-operated override unit, such as a push button and / or comprised in the user interface 12. As described hereinbefore, the control system 8 comprises a user interface 12. In the embodiment shown in Figure 2, the user interface comprises a visual display 60 for displaying information and parameters relating to the procedure, the operation of the various components and information regarding the state of the subject 2. In addition, the embodiment shown in Figure 2 comprises a touch pad 62 for the user to input data, settings and commands. The touch pad may be omitted in embodiments where the display is a touch screen allowing data input. In operation, the system shown in Figures 1 and 2 functions as follows: The laser assembly 4 is used to carry an endoscopic procedure, such as laser lithotripsy in a known manner. During this procedure, the laser assembly 4 is operated to generate a beam of light, which is conveyed to a treatment location within the urinary collection system of the subject 2 by the ureteroscope 4a. The urinary collection system of the subject 2 is irrigated by the irrigation system 6 in a known manner by provided a flow of pressurised irrigation fluid to the urinary collection system of the subject 2 by the feed conduit 6a. In the embodiment shown in Figure 2, the irrigation fluid is fed to the subject by the peristaltic pump 30 from the reservoir 32. Sensors within the urinary collection system of the subject 2 sense the pressure and the temperature of the fluid within the urinary collection system. Signals with data relating to the pressure and temperature prevailing in the urinary collection system are provided to the control unit 10 along the signal line 10a. The control unit 10 is provided with a threshold pressure and a threshold temperature. The threshold values may be preset within the control unit 10. Alternatively or in addition, the user interface 12 may allow the user, such as a surgeon, to input into the control unit 10 threshold values for pressure and temperature. In the event the pressure sensed by the sensors within the urinary collection system of the subject 2 exceeds the threshold pressure, the control unit 10 acts to reduce the pressure of the irrigation fluid being fed to the subject through the line 6a. The control unit 10 may adjust the operation of the pump 30, such that the output pressure of the pump is reduced. Alternatively, the control unit 10 may turn off the pump 30. Should a problem arise and the control unit 10 be unable to adjust the irrigation fluid pressure as required, the control unit may operate to shut the control valve 36 in the feed line 6a, thus stopping the flow of irrigation fluid to the subject. Once the sensed pressure within the urinary collection system of the subject returns to an acceptable level below the threshold pressure of the control unit, the control unit 10 will activate the pump 30 and / or the control valve 36, as required, to restore or increase the flow of irrigation fluid to the subject. In the event the temperature sensed by the sensors within the urinary collection system of the subject 2 exceeds the threshold temperature of the control unit 10, the control unit 10 acts to reduce the energy being output by the laser assembly 4 and provided to the treatment location within the urinary collection system of the subject 2. Where the laser assembly 4 permits, the control unit 10 may vary the operation of the laser assembly to reduce the energy being output. Alternatively, the control unit 10 may switch off the laser assembly 4. This may be achieved using the cut-off switch 54 in the power supply cable 52 of the laser assembly 4. In this way, no modification of or direct interaction with the laser assembly 4 is required. The system shown in Figure 2 provides the user with an override facility, allowing the user, such as a surgeon, to override the action of the control unit to shut down the laser assembly 4 and permit continued operation. This option may be exercised where the user, such as a surgeon, considers it acceptable to continue the laser treatment. Data received by the control unit 10 from the pressure sensor 42 and the temperature sensor 44 relating to the conditions of the irrigation fluid leaving the subject are used to identify abnormal operation of the system, for example a blockage preventing the irrigation fluid from reaching the treatment site within the urinary collection system of the subject. Data received by the control unit 10 from the pressure sensor 72 regarding the prevailing ambient air pressure, allow the control unit 10 to determine the pressure of the irrigation fluid in both relative and absolute terms. These pressure data are displayed to the user, who may select the displayed pressure values to be in either one or both of relative or absolute pressures. The user interface 12 provides a visual display, preferably a touch-screen display, to the user by way of the display 60. The visual display may show any suitable parameters during the procedure. In the event of a sensed pressure or temperature within the urinary collection system of the subject being above the threshold values of the control unit, the user interface displays a visual warning to the user. Preferably, the user interface 12 also provides an audible warning when a threshold has been exceeded. With reference to Figure 3, there is shown one embodiment of a sensor assembly for use in sensing pressure and / or temperature at an in vivo location within the urinary collection system of the subject 2. The sensor assembly, generally indicated as 102 comprises a MEMS sensor 104, such as a SMI-1 Intrasense sensor from TE Connectivity. The sensor 104 is configured to sense both pressure and temperature of the surrounding fluid. The sensor 104 is disposed in the end portion 106 of a 3 French tube 108, with the distal end 104a of the sensor 104 substantially flush with the open end of the tube 108. A lead 110 extends proximally from the sensor 104 along the tube. In use, the sensor assembly 102 is deployed within the urinary collection system of the subject 2, with the open end of the tube 108 and the distal end 104a of the sensor 104 exposed to the fluid within the urinary collection system. This arrangement is shown diagrammatically in Figure 4. Figure 4 is a representation of one side of the renal system of the subject. The renal system comprises a kidney 200, from which extends a ureter 202 to a bladder 204. A urethra 206 extends from the bladder 204. The kidney comprises a renal pelvis 208 and a plurality of calyxes 210. As represented in Figure 4, a sensor assembly 102 of the present invention extends through the upper region of the ureter 202 with the sensor disposed in a lobe of the kidney 200, having been introduced through the urethra 206 and the bladder 204 in known manner. 5

Claims

1. A system for controlling a laser assembly during an endourological procedure being conducted on a subject, the system comprising:an irrigation system comprising:a fluid delivery system comprising a pump for delivering an irrigation fluid intra-renally to the subject from an irrigation fluid reservoir;anda control system comprising:a temperature sensor for disposing at an intra-renal location within the subject and operable to generate a temperature signal corresponding to the temperature at the intra-renal location;a pressure sensor for disposing at an intra-renal location within the subject and operable to generate a pressure signal corresponding to the pressure of fluid at the intra-renal location;wherein the temperature sensor and / or the pressure sensor are housed within a tube having an outer diameter of up to and including 6 French (2 mm), wherein the tube has an open end and an end portion for disposing at an intra-renal location within the subject, wherein the temperature sensor and / or the pressure sensor are disposed at or adjacent the open end of the tube or wherein the temperature sensor and / or the pressure sensor are disposed within the tube and extend to the end portion of the tube spaced from the open end of the tube;anda control unit operable to:receive the temperature signal and vary the operation of the laser assembly when the temperature at the intra-renal location exceeds a threshold temperature; andreceive the pressure signal and control the operation of the pump to vary the fluid pressure at the intra-renal location.

2. The system for controlling a laser assembly according to claim 1, wherein the pump is a peristaltic pump.

3. The system for controlling a laser assembly according to any preceding claim, wherein the irrigation system further comprises a fail-safe system operable in the event there is a problem with the operation of the irrigation system to stop the flow of irrigation fluid to the subject.

4. The system for controlling a laser assembly according to any preceding claim, wherein the temperature sensor and / or the pressure sensor are configured to be inserted into and located within the renal pelvis of a kidney of the subject.

5. The system for controlling a laser assembly according to any preceding claim, wherein the temperature sensor and / or the pressure sensor are housed within a 3 French (1 mm) tube.

6. The system for controlling a laser assembly according to any preceding claim, wherein the system comprises a sensor configured to sense both temperature and pressure.

7. The system for controlling a laser assembly according to any preceding claim, wherein the temperature and / or the pressure sensor is a Micro Electro Mechanical Systems (MEMS) sensor.

8. The system for controlling a laser assembly according to any preceding claim, wherein the irrigation system comprises a conduit for returning fluid from within the subject, the control system further comprising one or more sensors to sense one or both of the temperature and pressure of the fluid being returned; signals from the or each of the one or more sensors being provided to the control unit.

9. The system for controlling a laser assembly according to any preceding claim, wherein the control system further comprises a pressure sensor for sensing the prevailing ambient pressure; signals from the pressure sensor being provided to the control unit.

10. The system for controlling a laser assembly according to any preceding claim, wherein the control unit is provided with a preset threshold pressure value and / or a preset threshold temperature value.

11. The system for controlling a laser assembly according to any preceding claim, further comprising a manual override, the manual override being operable by a user to override the action of the control unit to vary the operation of the laserand / or to override the action of the control unit to vary the operation of the irrigation system.

12. The system for controlling a laser assembly according to any preceding claim, wherein the control unit is operable to cut off the supply of electrical power to the laser assembly in the event a temperature within the subject exceeding the threshold temperature is sensed by the temperature sensor.

13. The system for controlling a laser assembly according to any preceding claim, wherein the control system further comprises a user interface operable to provide the user with an indication of one or more parameters during the procedure and / or allow the user to input into the control unit settings for carrying out the procedure.

14. The system for controlling a laser assembly according to claim 13, wherein the user interface comprises a touch-screen display unit.

15. The system for controlling a laser assembly according to any preceding claim, wherein the control unit is configured to transmit data relating to the procedure to a patient record system.

16. A system for conducting an endourological procedure employing a laser assembly, more especially a laser lithotripsy procedure on a subject, the system comprising:a laser assembly for generating a laser beam for deploying at an in vivo location within the endourological system of the subject; anda system for controlling a laser assembly according to any preceding claim.29 01 24

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