Predictors of metachronous inguinal hernias in children

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. 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. 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%). 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.