Predictive model for contralateral inguinal hernia repair within three years of primary repair: a nationwide population-based cohort study

Background Limited reports have discussed the risk factors for contralateral inguinal hernia (CIH) repair. We generated a risk factor scoring system to predict CIH within 3 years after unilateral inguinal hernia repair. Methods We extracted the admission data of patients aged >= 18 years who underwent primary unilateral inguinal hernia repair without any other operation from the National Health Insurance Research Database. Patients were randomly divided into 80% and 20% validation cohorts. Multivariate analysis with a logistic regression model was used to generate the scoring system, which was used in the validation group. Results Overall, 170,492 adult men were included, with a median follow-up of 87 months. The scoring system ranged from 0-5 points, composited with age (< 45 years, 0 points; 45-65 years, 2 points; 65-80 years, 3 points; > 80 years, 2 points) and two comorbidities (cirrhosis and prostate disease: 1 point each). The areas under receiver operating characteristic (ROC) curves were 0.606 and 0.551 for the derivation and validation groups, respectively. The rates and adjusted odds ratios (OR) of CIH repair in the derivation group were 3.0% at 0-2 points, 5.5% (1.854, p < 0.001) at 3, 6.7% (2.279, p < 0.001) at 4, and 6.9% (2.348, p < 0.001) at 5, with similar results in the validation group [2.3% at 0-2 points, 3.8% (1.668, p < 0.001) at 3, 5.4% (2.386, p < 0.001) at 4, and 6.8% (3.033, p < 0.001) at 5]. Conclusions The CIH scoring system effectively predicted CIH repair within three years of primary unilateral inguinal hernia repair. Surgeons could perform laparoscopic surgery with CIH scores > 2 points which enables easier contralateral exploration and repair during the same surgery, without additional incisions, to minimize the need for future surgeries. However, further prospective validation of this scoring system is required.