BACKGROUND: To investigate the relation between groin hernia subtypes in patients operated for bilateral hernias.

METHODS: With data from the Danish Hernia Database, we identified all patients operated for primary groin hernias from 1998 to 2012. Within this cohort all patients that were bilaterally operated were analyzed. Risk factors for bilateral groin hernia operation as well as the relationship between groin hernia subtypes bilaterally, were analyzed using multivariate Cox proportional hazards analysis and Kappa statistics.

RESULTS: A total of 108, 775 persons with primary groin hernia repair (89.9% males) were registered, and of those were 12,041 persons operated bilaterally (94.9% males). Females and males operated for a unilaterally direct inguinal hernia (DIH) had increased Hazard Ratios (HR) of 3.85 (CI 95% 2.14-6.19) and 4.46 (CI 95% 2.57-7.88) of being contralaterally operated for a DIH. Females and males operated for a unilaterally indirect inguinal hernia (IIH) had HRs of 6.93 (CI 95% 3.66-13.11) and 1.89 (CI95% 1.24-2.88) for being contralaterally operated for an IIH. The same tendency was seen for femoral hernias.

CONCLUSIONS: All hernia subtypes were bilaterally associated in both genders and the hernia subtypes could be localized manifestations of generalized conditions or inheritable traits instead of localized defects.