In accordance with the present invention, there are provided methods for identifying the 
sentinel lymph node in a drainage field for a tissue or organ in a subject. In select embodiments, the invention allows for the identification of the first or 
sentinel lymph node that drains the tissue or organ, particularly those tissues associated with neoplastic or infectious diseases and disorders, and within the pertinent 
lymph drainage basin. Once the 
drainage basin from the tissue or organ, i.e., the 
sentinel lymph node, is identified, a pre-operative or intraoperative mapping of the affected lymphatic structure can be carried out with a contrast agent. Identification of the first or sentinel 
lymph node, on the most direct drainage pathway in the drainage field, can be accomplished by a variety of imaging techniques, including 
ultrasound, MRI, CT, nuclear and others. Moreover, once the lymphatic structure is identified as being associated with neoplastic or infectious diseases and disorders, the affected lymphatic structure can be removed surgically or by a suitable minimally 
invasive procedure to allow 
pathological analysis to be performed to determine whether certain diseases or disorders exist, without resort to more radical lymphadenectomy. Further, the agent can be made to carry diagnostic or therapeutic probes to be activated and / or delivered to the 
injection site or any part of the lymphatic pathway downstream from the 
injection site.