Varicocele has been repeatedly implicated as a cause of infertility in selected men, although neither a causal relationship nor a mechanism has been documented. The purpose of this investigation was to create a varicocele model in animals and to study the subsequent alterations in testicular physiology. Secondary dilation of the left internal spermatic vein was achieved either by parital ligation of the left renal vein in rats and dogs or by surgical destruction of the valve of the left testicular vein in a second group of dogs. 1 mo after partial ligation in the rats and 3 mo after partial ligation or valve destruction in the dogs, testicular blood flow was measured using Strontium 85 (SR-85)-labeled microspheres (15±1.1 μm). Intratesticular temperature was measured with a Bailey needle probe thermometer and biopsies were obtained for histologic sections. Mean testicular blood flow in milliliters per minute per 100 g was significantly greater in the partially ligated rats; right testis control 26±2, left testis control 24±2 compared to right testis experimental 35±3, left testis experimental 35±4 (P < 0.02). Dogs undergoing either partial vein ligation or valve destruction showed similar increases in mean testicular blood flow; right testis control 8±1, left testis control 8±1 vs. right testis experimental 16±3, left testis experimental 18±4 (P < 0.01). The mean difference between intratesticular and intraperitoneal temperature in control rats was significantly higher (4.02±0.25°C right testis, 3.77±0.14°C left testis), than rats who underwent partial vein ligation (right testis, 2.14±0.09°C, left testis 2.34±0.12°C) (P < 0.001). Control dogs also had a significantly higher mean difference between intratesticular and rectal temperatures; (right testis control 3.61±0.42°C, left testis control 3.60±0.40°C) than the partially ligated or valve destruction dogs (right testis 2.31±0.17°C, left testis 2.67±0.32°C) (P < 0.05). In addition, histologic evaluation revealed abnormalities in spermatogenesis in some of the animals. Thus, venous dilatation secondary to partial vein ligation or testicular vein valve obliteration is followed by large bilateral increases in testicular blood flow in these two species. A consequence of this increased flow is an elevation in bilateral testicular temperature, which it is postulated, leads to impaired spermatogenesis in some of the animals. In selected men varicocele may impair spermatogenesis by a similar physiologic mechanism.
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