title: Systematic review of the risk of developing a metachronous contralateral inguinal hernia in children.
abstract: 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).
  
  
  CONCLUSIONS
  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.
authors.affiliation: Department of Paediatric Surgery, Institute of Child Health and Great Ormond Street Hospital for Children, London, UK.
authors.forename: O
authors.initials: O
authors.lastname: Ron
authors.forename: S
authors.initials: S
authors.lastname: Eaton
authors.forename: A
authors.initials: A
authors.lastname: Pierro
mesh_terms: D000293:Adolescent; D017668:Age of Onset; D002648:Child; D002675:Child, Preschool; D005260:Female; D005500:Follow-Up Studies; D006552:Hernia, Inguinal / Q000209:etiology* / Q000473:pathology; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D008297:Male; D012008:Recurrence; D018570:Risk Assessment; D012307:Risk Factors; D012737:Sex Factors; D013997:Time Factors