Systematic review of the risk of developing a metachronous contralateral inguinal hernia in children

Background: This study aims to establish the risk of developing a metachronous contralateral inguinal hernia (MCIH) following open repair of a unilateral inguinal hernia in children. Methods: A systematic review was performed using a defined search strategy. Studies in which children undergoing open repair of a unilateral inguinal hernia without contralateral exploration and who were followed up for MCIH development were included. Results: Of 5937 titles and abstracts screened, 154 full-text articles were identified for review; 49 papers were analysed with data on 22 846 children. The incidence of MCIH was 7.2 per cent overall, 6.9 per cent in boys and 7.3 per cent in girls (P = 0.381). Children with a left-sided inguinal hernia had a significantly higher risk of developing a MCIH than those with a right-sided hernia (10.2 versus 6.3 per cent respectively; P < 0.001). Conclusion: Overall, in both boys and girls, 14 contralateral explorations are required to prevent one metachronous hernia. The risk of developing a MCIH appears unchanged in early childhood, with a slight reduction after 12 years of age. Children with a left-sided hernia have the greatest risk of developing a contralateral hernia, but ten explorations are still required to prevent one metachronous hernia. Most MCIHs occur in the first 5 years after unilateral inguinal hernia repair.