'Testis-epididymis dissociation' in cryptorchidism and hydrocele: the tip of the iceberg of a persistent genital mesentery.

Purpose: To investigate whether testis-epididymis dissociation encountered in boys with cryptorchidism/hydrocele is related with an abnormal persistence of the fetal mesentery of testis and associated ducts.

Methods: We examined the morphology of peritoneal folds of the testis, epididymis, and vas deferens in 25 boys operated for unilateral cryptorchidism [inguinal (n = 20), intrabdominal (n = 5)] and 20 boys operated for unilateral communicating hydrocele. Findings were compared with the normally persisting genital mesentery of rats (n = 30, both sides), a known animal model of the genital mesentery of human fetuses, as well as with the normal mature pattern of genital peritoneal folds in adult male cadavers (n = 12, both sides). Rats before testis descent [aged 18 days (n = 15)] served for comparison with boys with cryptorchidism, while rats after testis descent [aged 50 (n = 15)] known to retain patent processi vaginales for comparison with boys with hydrocele.

Results: A well-developed genital mesentery, identical to the fetal-type genital mesentery in the rat, was documented in cryptorchidism and hydrocele. The peritoneum enveloped the testis, epididymis, and vas deferens, and formed wide ligaments between testis-epididymis, epididymis-vas deferens, and vas-posterior wall; processus vaginalis was patent in all cases. The testis-epididymis ligament was related with testis-epididymis distancing, the so-called testis-epididymis dissociation. On the contrary, genital mesentery had involuted in the adult male cadavers, except for a small portion of testis-epididymis ligament corresponding to the so-called sinus epididymis.

Conclusion: The testis-epididymis dissociation encountered in cryptorchidism/hydrocele is part of an anomalously persisting fetal-type genital mesentery.