Incidence and risk factors of parastomal hernia after ileal conduit diversion in Japanese population.

Objectives: To determine risk factors influencing the incidence of parastomal hernia (PH) associated with ileal conduit (IC).

Methods: A total of 194 Japanese patients who underwent IC diversion followed by regular postoperative radiographic follow-up from 2005 through 2016 were enrolled. The diagnosis of PH was determined by computed tomography (CT) for patients with and without related symptoms. The cumulative incidence of PH was assessed by the Kaplan-Meier method. The log-rank test and a multivariate Cox proportional hazards model were used to evaluate risk factors associated with the incidence of PH.

Results: PH was observed in 20 patients (10.3%) after a median follow-up of 25.5 months. Of the 20 patients, three were symptomatic. The cumulative incidences were 3.6%, 10.1% and 15.1% at 1, 2 and 5 years after operation, respectively. The median body mass index (BMI) was 23.1 kg/m (IQR 20.4-24.6). The BMI and diameter of the passage through the rectus abdominis muscle for the IC (DPRAM) were significant predictors for PH (p = 0.04 and p < 0.001, respectively). In proportional hazards regression analysis, DPRAM ≥ 2.4 cm was the only independent risk factor for developing PH (HR 10.94, 95% CI 3.66-32.64).

Conclusions: The incidence of PH in the current Japanese series was relatively low. Even in the population with low BMI, higher BMI might have an impact on incidence of PH. Moreover, DPRAM was also significantly associated with the incidence, suggesting that the operative procedure for creation of the passage is critical for future development of PH.