Histological evaluation of ureteral involvement in women with deep infiltrating endometriosis: analysis of a large series.

STUDY QUESTION: In women with deeply infiltrating endometriosis (DIE) what is the prevalence of involvement of endometriotic tissue and fibrosis in ureteral endometriosis (UE), as assessed by histological staining? SUMMARY ANSWER: In women with DIE, ureteral involvement is more often due to endometriotic tissue rather than fibrosis. WHAT IS KNOWN ALREADY: In the current literature, histological evaluation of ureteral endometriosis is mainly based on the degree of wall infiltration by endometriosis instead of the tissue composition. A few studies reported ill-defined and contradictory histological data on the tissue composition of UE. STUDY DESIGN, SIZE, DURATION: Retrospective observational study based on clinical records of women affected by DIE, laparoscopically treated for UE at a tertiary referral center, between January 2010 and March 2013. All cases of ureteral nodule excision or ureterectomy with histological examination of the specimens were included. Exclusion criteria were other identified causes of hydroureteronephrosis, medical therapy for a period of at least 3 months before surgery and previous surgery for DIE. PARTICIPANTS/MATERIALS, SETTING, METHODS: A total of 77 patients were included in the study and among them seven (9%) presented with bilateral ureteral involvement, giving a total of 84 cases of UE available for analysis. All patients had stage IV endometriosis. According, respectively, to the presence of endometrial glands and/or stroma cells or of fibrotic tissue only, the endometriotic UE and fibrotic UE groups were compared with regard to hydroureteronephrosis at pre-operative urinary tract computerized tomography scan, type of surgical procedure performed to treat UE (nodule removal or ureterectomy), association with other locations of the disease and post-operative complications (ureteral fistula or stenosis). MAIN RESULTS AND THE ROLE OF CHANCE: For the 84 cases of UE, 65 (77%) and 19 (23%), respectively, showed endometriotic tissue and fibrotic tissue only. Presence of hydroureteronephrosis and endometriotic pattern of UE showed a significant association [endometriotic UE 44/65 (68%) versus fibrotic UE 8/19 (42%); P = 0.04]. Fibrotic pattern of UE and presence of concomitant recto-vaginal endometriosis showed a significant association [endometriotic group: 29/65 (45%) versus fibrotic group 18/19 (95%); P < 0.001]. LIMITATIONS, REASONS FOR CAUTION: The retrospective and monocentric (tertiary referral center) study design. WIDER IMPLICATIONS OF THE FINDINGS: Besides the distinction between extrinsic and intrinsic UE based on the degree of wall infiltration by endometriosis, a new classification according to the histological pattern of UE could be useful for clinicians, both in the diagnostic and therapeutic fields.