The relationship between the vas volume and the anatomic size of the vas deferens.

The anatomic sizes of 210 vas segments from 107 volunteers of vasectomy were measured by computerized image graphic technique with microphotography. The mean equivalent-round, outer and inner diameters of the vas were 2.17 +/- 0.20 mm and 0.56 +/- 0.08 mm, respectively. The calculated thickness of vas wall was 0.81 +/- 0.21 mm. The maximal volumes of 124 vas segments (1 cm in length) were tested by injecting colored solution into vas lumen until vas rupture. The mean rupture volume of 1 cm vas lumen was 0.05 +/- 0.007 mL. A significant influence of the thickness of vas wall (p < 0.05) and body height (p < 0.05) on the rupture volume was noticed in stepwise regression analysis. A tunnel-like rupturing pattern was observed in morphological observation. The obtained rupture volume provides a security line in determining the injection volume of occlusive material or the size of the implanted contraceptive device.