One third of patients with a unilateral palpable undescended testis have a contralateral patent processus.

PURPOSE: The purpose of this study was to determine the incidence and predictive factors associated with a contralateral patent processus vaginalis in boys with a unilateral palpable undescended testis.
METHODS: We retrospectively reviewed the records of 77 consecutive boys (median age, 15 months; range, 5 months to 17.7 years) who had undergone orchiopexy for a unilateral palpable testis. At inguinal orchiopexy, an 8F feeding tube and a 70° adult cystoscope lens were placed into the peritoneum through the hernia sac, and the contralateral internal ring was inspected. The clinical factors that might predict the presence of a contralateral patent processus vaginalis were determined.
RESULTS: The overall rate of a contralateral patent processus vaginalis was 34% in those with a significant ipsilateral hernia sac. After considering age, side, prematurity, location, and volume of the undescended testis, only the boys with a testis distal to the external ring compared with those with testes lying within the inguinal canal had statistically increased odds of a patent contralateral processus vaginalis (odds ratio, 3.1; 95% confidence interval, 1.08-9.08).
CONCLUSION: Approximately one third of boys with a unilateral palpable undescended testis will have a contralateral patent processus vaginalis as determined by transinguinal laparoscopy. The rate is higher (52%) if the undescended testis was distal to the external ring. Both the etiology and significance of this contralateral finding are unknown.