Stent Side Hole Tapering for Encrustation Reduction
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Solution Overview
Problem
Ureteric stents suffer from encrustation issues at side holes, leading to blockages and increased renal pelvic pressure, which complicates urine drainage and requires costly interventions, and existing solutions like metallic stents or surface coatings are either expensive or complex to produce.
Innovation Solution
A stent design with tapered side holes that reduce in thickness towards the upstream and downstream ends, and a method of forming these side holes using micro-milling, which minimizes encrustation without increasing production complexity or costs, regardless of the stent material or surface treatments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional circular side holes are used in stents, then urine drainage is enabled, but encrustation occurs at side holes leading to blockages and increased renal pelvic pressure
Solution Approach 1:
The side holes are designed with non-circular cross-sections (oval, rectangular, or triangular) and/or streamlined shapes that create specific flow patterns. This local geometric modification changes the fluid dynamics at the side holes, reducing flow stagnation and preventing encrustation while maintaining urine drainage functionality.
2Reliability
If metallic stents are used to reduce encrustation, then stent reliability improves, but manufacturing cost increases
Solution Approach 1:
The invention changes the geometric parameters of the side holes (cross-sectional shape and/or streamlined shape) rather than changing the bulk material. This allows the use of cost-effective polymer or silicone materials while achieving encrustation resistance through optimized side hole geometry, avoiding the need for expensive metallic materials.
3Reliability
If surface coatings are applied to reduce encrustation, then stent reliability improves, but device complexity increases
Solution Approach 1:
Instead of applying surface coatings to modify the stent surface properties, the invention inverts the approach by modifying the side hole geometry itself. The non-circular cross-section and streamlined shape create flow conditions that naturally prevent encrustation, eliminating the need for additional surface coating layers and their associated manufacturing complexity.
4Productivity
If tubular extrusions of side holes are used to improve drainage, then urine flow efficiency increases, but patient discomfort increases due to contact with inner ureter wall
Solution Approach 1:
The streamlined shape of the side holes is designed to optimize flow efficiency without creating protruding tubular extrusions. The geometric modification is confined to the side hole geometry itself, maintaining a smooth stent surface that does not contact or irritate the inner ureter wall, thus avoiding patient discomfort while still improving drainage efficiency.
Data Source
Figure 1~2(b)
Figure 3(a)~3(d)
Figure 4(a)~4(e)
AI summary
A stent (100) comprising a stent wall (102), the stent wall (102) having a plurality of side holes (110) extending therethrough, each side hole (110) having an upstream end (116) and a downstream end (118). The stent wall (102) tapers in thickness in a direction towards the side hole (110) at the upstream (116) and/or downstream (118) end of at least one of the side holes (110). Also disclosed are methods for making side holes (110) in stents (100) by milling and making stents (100) having side holes (110) by injection moulding.