Both irritable bowel syndrome and endometriosis are common conditions, although 
symptomatic gastrointestinal endometriosis is extremely rare. We report the case 
of a patient initially thought to have irritable bowel syndrome, in whom the 
diagnosis of endometriosis only became clear following a laparotomy for small 
bowel obstruction. This case highlights the need to question the diagnosis in 
patients with irritable bowel syndrome when there is any uncertainty, and also 
to appreciate that other pathology can arise, even when the diagnosis is secure.