Predictors of metachronous inguinal hernias in children.

Purpose: Surgical management of the contralateral groin in unilateral inguinal hernia remains controversial. Our aim was to determine predictors of metachronous inguinal hernias in children using multivariable analysis.

Methods: A retrospective cohort study of 6,302 patients presenting with inguinal hernia to a single surgeon's practice over 35 years was undertaken. Patients with bilateral hernias (n=698), contra-lateral groin exploration (n=235) or missing data (n=274) were excluded. Multiple forward logistic regression was used to predict metachronous hernia (MH). Entry into the model was with a P-value of 0.05 and exit was at 0.10. To account for the non-linear relationship of age at time of initial hernia, age was dichotomized into four quartiles.

Results: A total of 5,095 patients were eligible for inclusion [median age 2 years (range 1 month-18 years); males 84.4%; indirect type 99%]. In total, 267 (5.2%) patients developed a MH at a median time of 1 year. Predictors of developing a MH were the following: presentation with a left-sided hernia (OR=2.2, CI=1.7-2.8; P<0.0005) was associated with increased odds of MH, while age at initial presentation<6 months was associated with a reduced risk of MH (OR=0.39, CI=0.25-0.59; P<0.0005). Other co-variates [any age>6 months (P=0.35), gender (P=0.20) and history of incarceration (P=0.67), prematurity (P=0.94), twins (P=0.13), or ventriculo-peritoneal shunt (P=0.68)] were not associated with MH development. The rate of incarceration in patients who developed a MH was 2/267 (0.7%).

Conclusion: As the overall rate of metachronous inguinal hernias in children is low (5.2%) and the risk of incarceration is 0.7%, we do not advocate routine contralateral exploration. A primary left-sided hernia is associated with twofold increased odds of developing a contra-lateral hernia, within a median time of 1 year; therefore, this higher risk subpopulation should receive closer follow-up over this time period.