Effect of bilateral vasectomy on the structure and function of the testes

Abstract

The effect of bilateral vasectomy on the testis and epididymis was studied in adult dogs. Particular attention was given to the endocrine function of the organ, and the total content of testosterone-secreting Leydig cells was quantitatively estimated. Vasectomy produces a marked degeneration of the seminiferous tubules as well as some reduction in the testicular volume. Spermatogenesis ceases completely, but the basal cells or spermatogonia remain unaffected, which can explain how spermatogenesis can occur again under favourable circumstances after vasorrhaphy. There was no fibrosis, cellular infiltration, or necrosis. No signs of regeneration are found up to eight weeks after vasectomy. Whether regeneration occurs spontaneously or only after recanalization remains uncertain. The Leydig cell content of the canine testis was 1.58 ± 0.43 ml per testis, or approximately 15 per cent of the testicular volume. The few estimates available for man are closely similar. Leydig cells become more prominent after vasectomy. Quantitatively, they increase from 1.58 ± 0.43 ml to 1.87 ± 0.70 ml per testis—a modest but definite average increase of about 20 per cent. The histopathologic picture, however, gives a more exaggerated impression because of the simultaneous collapse and degeneration of the tubules. The possible implications of the increase in Leydig cells after vasectomy and the mechanisms involved are discussed. The effect of bilateral vasectomy on the testis and epididymis was studied in adult dogs. Particular attention was given to the endocrine function of the organ, and the total content of testosterone-secreting Leydig cells was quantitatively estimated. Vasectomy produces a marked degeneration of the seminiferous tubules as well as some reduction in the testicular volume. Spermatogenesis ceases completely, but the basal cells or spermatogonia remain unaffected, which can explain how spermatogenesis can occur again under favourable circumstances after vasorrhaphy. There was no fibrosis, cellular infiltration, or necrosis. No signs of regeneration are found up to eight weeks after vasectomy. Whether regeneration occurs spontaneously or only after recanalization remains uncertain. The Leydig cell content of the canine testis was 1.58 ± 0.43 ml per testis, or approximately 15 per cent of the testicular volume. The few estimates available for man are closely similar. Leydig cells become more prominent after vasectomy. Quantitatively, they increase from 1.58 ± 0.43 ml to 1.87 ± 0.70 ml per testis—a modest but definite average increase of about 20 per cent. The histopathologic picture, however, gives a more exaggerated impression because of the simultaneous collapse and degeneration of the tubules. The possible implications of the increase in Leydig cells after vasectomy and the mechanisms involved are discussed.