YY/T 0872-2013Test methods for ureteral stents (English PDF)

3.1 Artificial Urine

A solution of organic and inorganic compounds whose physical and chemical properties are close to those of normal human urine. Artificial urine is used instead of human urine to simulate the effect of human urine on ureteral stents.

3.2

Bladder Retention Means

The physical structure at the bladder end of the stent that prevents the stent from falling out of the bladder.

3.3 Break Strength

The maximum tensile load required to cause the stent to break.

3.4 Cross Section

A cross-sectional view of the stent tube perpendicular to the long axis of the stent.

3.5 Distal

The end furthest from the starting point. The distal end of the stent is the end placed in the bladder, also known as the bladder end.

3.6 Drainage Holes

The holes in the stent tube wall that allow urine to flow in and out of the stent lumen.

3.7 Dynamic Frictional Force

The resistance to motion generated between two surfaces in relative motion. The dynamic frictional force is defined as the dynamic friction coefficient multiplied by the force acting on the material surface in the direction perpendicular to the material surface.

3.8 Elongation

The increase in the length of the tube at the time of sample fracture, divided by its initial length, expressed as a percentage. The extension of the tube is caused by tensile load.

3.9 French Size

A unit of measurement used to indicate the specifications of tubular instruments; each unit is approximately equal to a diameter of 0.33 mm. Common French size markings are shown in

Table 1.

Table 1 3.10 Kidney Retention Means

The physical structure at the kidney end of the stent that prevents the stent from falling out of the kidney.

3.11 Length

The distance between the nearest part of the bladder positioning device and the farthest part of the kidney positioning device when the main axis of the stent is placed vertically on a plane (see Figure 1).

Figure 1 -- Determination of Stent Length

3.12 Lumen

The passageway inside the tube.

3.13 Proximal

The end closest to the starting point; in the urinary system, the renal end is considered the starting point. The proximal end of the stent is the end that is placed within the renal pelvis, also known as the renal end.

3.14 Radiopacity

The characteristic that indicates an instrument’s ability to absorb X-rays, which allows the instrument to be observed through X-ray films or fluorescent screens.

3.15 Referee Test Method

The method specified in published instrument standards. This method can be used to evaluate the performance of ureteral stents. Manufacturers are not required to use the referee test method for testing and quality control.

3.16 Retention Strength

The force required for the retention means of the extension stent.

3.17 Sterility

A state in which no surviving microorganisms exist.

3.18 Tolerance

The permissible deviation of the standard specification. The length tolerance of the ureteral stent is ±0.5 cm, and the outer diameter tolerance of the ureteral stent is ±0.01 mm, which is approximately 1/3 Fr.

3.19 Ureteral Stent

A tubular indwelling device implanted in the kidney, ureter, or bladder, with a fixed end of the tube in the kidney and bladder.

6.1 General Guidance

6.1.1

Actual ureteral stents should be used as samples, rather than sheets.

6.1.2

The sample size in all tests must be statistically significant.

6.1.3

Use commercially available sterilized products for testing.

6.1.4

Immerse the test samples in artificial urine at 37°C±3°C for 30 d. Any one of the two artificial urine formulations listed in Appendix A may be used.

6.1.5

Maintain the pH of the artificial urine within the range of 5.5 ~ 6.5 at all times. Artificial urine should be changed weekly.

6.1.6

Conduct the tests before immersion and at least 30 d after immersion. For products intended to undergo chemical/mechanical changes (such as softening, swelling, etc.), the initial mechanical test is only performed on the stent after it has been sufficiently immersed (enough to produce chemical/mechanical changes).

6.1.7

For dynamic frictional force tests, samples shall only be tested after immersion in distilled water for 1 min; the test shall not be repeated after 30 days of immersion.

6.2 Retention Strength

6.2.1 Scope of application

This test method determines the resistance to movement of a ureteral stent. It can be used to test the proximal or distal end of a ureteral stent.

6.2.2 Overview of test methods

6.2.2.1

The test apparatus is shown in Figure 2.The block-shaped flared end is made of polytetrafluoroethylene or polyoxymethylene resin. The area between the outer diameter of the stent and the inner diameter of the block-shaped flared end shall be clean. (Figure 2 also shows the flared end diameters corresponding to stents of different Fr specifications). […]