[Incidence of metachronic contralateral inguinal hernia]

There are many observational studies about the incidence of metachronous contralateral inguinal hernia (MIH). Metaanalysis allows to resume the results of individual studies in one with a higher level of evidence.

to know the incidence of MIH in order to decide the contralateral exploration.

We do an extensive bibliographic review in Medline, Embase and Cochrane Central. Data analysis is done with RevMan 4.2.

632 abstracts were screened by only one revisor who selected 27 studies: 17802 inguinal hernias and 1209 MIH. Follow up is between 6 months and 10 years. Due to high heterogeneity, a randomized effect analysis (Der Simonian and Lard) is done. The incidence of MIH is 6,96% (6,07-7,85); 14 hernia must be operated to avoid one MIH (NNT). If the original side of the hernia is left, the probability of MIH is 1.81 times higher (NNT =10). The secondary analysis indicates that there is no important publication bias.

Rutinary bilateral inguinal exploration is not justified. Only in high anaesthetic risk patients, bilateral exploration should be suggested.