Incidence of pediatric metachronous contralateral inguinal hernia and the relationship with contralateral patent processus vaginalis.

Background: The management of contralateral patent processus vaginalis (CPPV) in children with unilateral inguinal hernia is still controversial. The objective of this study was to verify the relationship between metachronous contralateral inguinal hernia (MCIH) and CPPV, and the risk factors of MCIH.

Methods: Children with unilateral inguinal hernia from three medical centers underwent either open or laparoscopic repairs. Clinical information, including demographics, morphological characteristics of CPPV, follow-up outcomes were collected.

Results: Among 2942 patients (92.2%) who received open repair with successful follow-up, 185 (6.29%) developed MCIHs [125 (10.9%) on the right side and 60 (3.3%)] on the left including 156 (7.07%) younger than 3 years old and 29 (3.94%) older than 3 years old. Patients younger than 3 years old with primary left inguinal hernias more easily develop MCIHs and the difference is statistically significant. Among 5370 patients (96.0%) who received laparoscopic repair with successful follow-up, the morphology of ipsilateral patent processus vaginalis were cavernous type in 5318 (99%) and 52 (1%) were fissure type. CPPVs were identified in 2233 (41.5%) cases [1256 (35.01%) on the left side and 977 (54.80%) on the right side, P < 0.001]; 1503 cases were cavernous type (1276 cases younger than 3 years old and 227 cases older than 3 years old) and 730 cases were fissure type (422 cases younger than 3 years old and 308 cases older than 3 years old). The probability of occurence of cavernous type and CPPV in children younger than 3 years old was higher than that in children older than 3 years old.

Conclusions: Not all CPPVS progress into an MIH, and approximate one of 15 CPPVs would progress into MIH. If patient with initial left-sided inguinal hernia is younger than 3 years old, when the morphology of CPPV is cavernous type identified by laparoscopic exploration, the contralateral repair would be recommended.