Original research article stabbing rectal pains, urinary frequency, dysuria, or pain with a full bladder (7, 8). There are a proportion of women who are asymptomatic. If symptoms are impacting on quality of life (QOL) then management options include analgesia, hormonal manipulation or surgery. Surgery for rectal endometriosis may involve 'shaving' of disease off bowel, excision of a small area (wedge) of anterior bowel wall or segmental resection. Complete excision of endometriosis has been found to provide long-term symptomatic relief (9-12); however, it is not without its complications. Surgical procedures extending to the pelvic side-wall may damage the autonomic nerve supply to the bladder, with dysfunction seen after both local excision of endometriosis and radical rectal resection (13). One systematic follow-up study including both techniques found transient voiding problems in almost all patients (14). Studies have demonstrated acute urinary retention in 6%-25% of patients after segmental rectal resection (3, 8, 10, 15-17); a recent review reported that the incidence of temporary bladder dysfunction after segmental resection was 8.1% (18).

Endometriosis is a common benign gynaecological disorder, which has an increased prevalence amongst twins and first degree relatives of affected individuals. Here we describe a case of remarkable resemblance in the distribution of deep infiltrating endometriosis related to the bowel in a monozygotic twin pair. We provide a literature review of studies of endometriosis in twins. We propose that genetic factors influence the nature and distribution of the disease, while environmental factors may affect the severity.