This paper is the 10th report in a series of studies on the application of microexplosion to medicine and biology.
In the application of microexplosion for destruction of ureteral calculi, the mechanical property of the ureter is an important factor for the prevention of complication. To clarify the factor in humans, tensile and expansive tests were performed on the middle portion of the normal ureter taken from fresh cadavers.
Tensile test:
Tensile test was performed using 11 ureters in the longitudinal direction and 7 in the transverse direction.
1) In the both directions a 3-phase curve was obtained between the elongation of the specimen and the load, turning at the two yield points. It was presumed that a small part of the mural element of the ureter was first torn at the first yield point, then all the element followed at the second point.
2) At the each yield point the tensile strength and maximum tensile stress of the transverse direction of the ureter were weaker than those of the longitudinal direction, although the elongation ratio at the two yield points was similar in the both directions. It was presumed, accordingly, that ureteral injury first occurred in the transverse direction.
3) The maximum tensile stress of the ureter was higher than that of the bladder.
Expansive test:
Expansive test was performed using 10 ureters.
1) At a leakage point, the internal pressure of the ureter was 1.9kgf/cm² and the internal diameter was 6.4mm on average.
2) At the leakage point, the tensile strength and elongation ratio of the external diameter were 0.71kgf/cm and 0.80 on average, respectively. The values were approximately equal to those of the tensile strength and elongation ratio measured by tensile test in the transverse direction.
It was thought from the results that the ureter was more suitable than the bladder for the application of microexplosion. However, if a conventional apparatus for the method is employed directly in the ureter, ureteral injury may occur by the generated gas because of the too small diameter of the ureter at the leakage point. The development of a new type of device is required for microexplosion ureterolithotripsy.