BILATERAL CRYPTORCHIDISM IN A DOG WITH PERSISTENT CRANIAL TESTIS SUSPENSORY LIGAMENTS AND INVERTED GUBERNACULA - REPORT OF A CASE WITH IMPLICATIONS FOR UNDERSTANDING NORMAL AND ABERRANT TESTIS DESCENT

The genital system of a dog with bilateral intra-abdominal testes is d escribed. External virilisation was normal except for an empty scrotum . Internally there was a prostate of normal macroscopic and histologic al appearances and, bilaterally, a fully developed male genital tract. Testicular vasculature was normal. Cranial to each testis, there was a strong ligament lying at the free edge of the gonadal/genital mesent ery and running between the cranial tip of the testis/epididymis and t he area craniolateral of the ipsilateral kidney. It was impossible to push the testes into the inguinal canal because of this strong ligamen t. Caudal to each testis, there was an elongated whitish structure bet ween the caudal pole of the epididymis and the area of the internal in guinal ring. On closer inspection this structure appeared to be the in verted and elongated processus vaginalis sac. There was a minor ligame nt at the free border of the inguinal fold of the genital mesentery be tween the tip of this inverted processus vaginalis and the adjacent ju nction of the cauda epididymidis and vas deferens. The findings sugges t that persistence of the fetal cranial gonadal suspensory ligaments c ould have been the major aetiological factor in this case of cryptorch idism. Their persistence could have prevented caudal outgrowth of the processus vaginalis with its consequent development into an intra-abdo minal papilla-like structure. Inappropriate persistence of the cranial suspensory ligaments in male rodents, pig, and cattle has been associ ated with insufficient exposure of their primordia to androgen during fetal life. It is uncertain whether a similar deficiency could underli e persistence of these structures in the present specimen. The finding s add further weight to the hypothesis that regression of the cranial gonadal suspensory ligament in males is a key event in the process of testis descent. The human homologue of this ligament deserves more att ention in the analysis and treatment of human cryptorchidism.