Incidence and risk factors of metachronous contralateral inguinal hernia development up to 25 years after unilateral inguinal hernia repair: a single-centre retrospective cohort study.

BACKGROUND: Patients undergoing unilateral inguinal hernia repair (IHR) are at risk of metachronous contralateral inguinal hernia (MCIH) development. We evaluated incidence and risk factors of MCIH development up to 25 years after unilateral IHR to determine possible indications for concomitant prophylactic surgery of the contralateral groin at the time of primary surgery. METHODS: Patients between 18 and 70 years of age undergoing elective unilateral IHR in the University Hospital of Leuven from 1995 to 1999 were studied retrospectively using the electronic health records and prospectively via phone calls. Study aims were MCIH incidence and risk factor determination. Kaplan-Meier curves were constructed and univariable and multivariable Cox regressions were performed. RESULTS: 758 patients were included (91% male, median age 53 years). Median follow-up time was 21.75 years. The incidence of operated MCIH after 5 years was 5.6%, after 15 years 16.1%, and after 25 years 24.7%. The incidence of both operated and non-operated MCIH after 5 years was 5.9%, after 15 years 16.7%, and after 25 years 29.0%. MCIH risk increased with older age and decreased in primary right-sided IHR and higher BMI at primary surgery. CONCLUSION: The overall incidence of MCIH after 25-year follow-up is 29.0%. Potential risk factors for the development of a MCIH are primary left-sided inguinal hernia repair, lower BMI, and older age. When considering prophylactic repair, we suggest a patient-specific approach taking into account these risk factors, the surgical approach and the risk factors for chronic postoperative inguinal pain.