ÆTIOLOGY OF THE IDIOPATHIC HYDROCELE

SUMMARY There are few (possibly no) lymphatics in the normal testis, epididymis, and visceral layer of the tunica vaginalis. The small quantity of fluid present in the healthy vaginal sac represents the testicular lymph. In the idiopathic hydrocele the testis is normal and there is no evidence to suggest over‐production of fluid (although over‐production must be the case where fluid from secondary hydroceles contains high concentrations of enzymes, etc.). Normal constituents of plasma have been extracted from idiopathic hydrocele fluid, but always in a lower concentration, and the larger the molecules the smaller is their concentration in the hydrocele fluid in comparison with the blood. Hydrocele fluid has the composition of a transudate. No active exudative process needs to be postulated. Absorption of the fluid must be via the lymphatic system. Spermatic veins contain no valves: neither varicocele, nor a life spent in hot countries, nor congestive cardiac failure, is associated with idiopathic hydroceles. Ascites, in contrast to what would be anticipated from the developmental linkage between the processus vaginalis and the peritoneum, is not associated with hydrocele. Urinary excretion of chemicals injected into the normal sac is much slower than would be expected were absorption taking place into blood capillaries. With similar injections made into idiopathic hydroceles absorption is slower still, yet there are abundant blood capillaries. There is convincing direct evidence that the lymphatic vessels are absent from the parietal layer of the tunica vaginalis in idiopathic hydroceles, and from the processus vaginalis in babies with hydroceles. A weakened cremaster muscle, the pressure from a truss, from a hernial sac, or from an epididymal cyst–all hinder the lymphatic return. In filarial hydroceles there is lymphatic, but not vascular, obstruction. Hydrocele fluid collects because of failure of lymphatic absorption. Later, the sac wall thickens and prevents further absorption. It seems probable that low‐grade inflammatory lesions of the epididymis in older men, and trauma in young men, damage lymphatic vessels, all of which pass over the surface of the epididymis on their way up to the cord. An “idiopathic” hydrocele follows.