Recurrent endometriosis: a battle against an unknown enemy

Recurrence of endometriosis after conservative surgery is not an uncommon finding. There is no uniformity, however, on what the term 'recurrence' means. Recurrence is variously defined in the literature as the relapse of pain, clinical or instrumental detection of an endometriotic lesion, repeat rise in CA 125 levels, or evidence of recurrence found during repeat surgery. Consequently, the reported recurrence rate varies widely (0-89%) in the different series, depending on its definition and the type of study performed. As endometriosis recurrence seems to be an indeterminate enemy, we set out to examine exactly what we were fighting in our everyday battle. In this narrative review, we aimed to seek an answer to questions related to endometriosis recurrence, some of which are often asked by our patients.