The myth of rectovaginal septum endometriosis - research letter

Sep 30, 2026

Endometriosis is a chronic inflammatory condition commonly linked to pain and infertility, and deep endometriosis (DE) involving the rectovaginal septum (RVS) has long been taught as a frequent site. This research letter reports a prospective observational study of 161 patients using advanced ultrasound, meticulous keyhole surgery, and tissue analysis. No endometriosis was found within the RVS; lesions were instead located in surrounding structures such as the uterosacral ligaments, the rectouterine pouch, or the bowel. Findings challenge established terminology and aim to improve diagnosis, surgical approach, and clinical communication.

LanguageEnglish

CategoryHealthcare

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Pages3

Reading Time8 min

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Reproduction & Fertility (2026) 7 RAF250164 [https://doi.org/10.1530/RAF-25-0164](https://doi.org/10.1530/RAF-25-0164) RESEARCH LETTER Received 15 October 2025 Accepted 15 December 2025 Available online 16 December 2025 Version of Record published 5 January 2026 | The myth of rectovaginal septum endometriosis
M Leonardi􀀁1, M Marien1, S J Dedden2, G Condous3 and S M Freger􀀁1
1Department of Obstetrics and Gynecology, McMaster University, Hamilton, Canada
2Department of Gynecology, Amphia Hospital, Breda, Netherlands
3The University of Sydney, Nepean Clinical School, Kingswood, Sydney, New South Wales, Australia
Correspondence should be addressed to S M Freger: [Fregers@mcmaster.ca](Fregers@mcmaster.ca) | | --- | | Lay summary
Endometriosis is a chronic condition where tissue resembling the uterine lining grows elsewhere in the pelvis, often causing pain, infertility, and inﬂammation. For decades, textbooks and research papers have described therectovaginal septum (RVS), the thin layer between the vagina and rectum, as a common site of deep endometriosis. Yet this belief has never been conclusively proven. In our study of 161 patients, combining advanced ultrasound, meticulous keyhole surgery, and tissue analysis, we found no evidence of endometriosis within the RVS. Instead, all lesions were located in surrounding structures, including the uterosacral ligaments, the rectouterine pouch, or the bowel. These ﬁndings challenge a long-standing anatomical misconception and call for the retirement of outdated terminology. Clarifying where endometriosis truly occurs is critical for improving diagnosis, surgery, and communication in women’s health. Our study overturns decades of dogma by showing that ‘rectovaginal septum endometriosis’ may be a myth.
Keywords: endometriosis; terminology; rectovaginal septum | Introduction Endometriosis is a chronic inﬂammatory disease often causing pain and infertility (International Working Group of AAGL, ESGE, ESHRE and WES et al. 2021) . The IDEA group has aimed to overcome longstanding diagnostic and terminology inconsistencies (Guerriero et al. 2016), particularly regarding deep endometriosis (DE) in the rectovaginal septum (RVS), historically reported in up to 52% of cases (Guerriero et al. 2008) . The 2016 Cochrane review further illustrates the lack of consensus, presenting multiple deﬁnitions of RVS involvement and heterogeneous diagnostic accuracy (Nisenblat et al. 2016) . The RVS is a retroperitoneal space (Fig. 1) long described as a common DE site; however, this interpretation is frequently confounded by severe adhesions in the rectouterine pouch (RUP) that obscure the peritoneal reﬂection. Although RVSinﬁltration is anatomically plausible via the peritoneal reﬂection and has been historically described, including through possible retrograde menstruation or Müllerian metaplasia, its true prevalence remains uncertain and likely overestimated. Additional confusion arises from the broad term ‘rectovaginal endometriosis’ (RVE), often applied to any lesion between the rectum and vagina, even when neither structure is inﬁltrated. This semantic overlap contributes to the misclassiﬁcation of lesions in the posterior compartment as ‘RVS’endometriosis. Methods We conducted a prospective observational study at the McMaster University Endometriosis Clinic from November 2021 to January 2023 to determine endometriosis distribution with a modern approach, combining ultrasound, surgery, and histopathology, and conforming to the latest International Terminology deﬁnitions of DE as any lesion with inﬁltration depth Published by Bioscientiﬁca Ltd. [https://raf.bioscienti](https://raf.bioscienti)ﬁ[ca.com](ca.com) © 2026 the author(s) This work is licensed under a Creative Commons Attribution 4 .0 International License. M Leonardi et al. Reproduction & Fertility (2026) 7 RAF250164 [https://doi.org/10.1530/RAF-25-0164](https://doi.org/10.1530/RAF-25-0164) F

FAQs

What does the study challenge about rectovaginal septum endometriosis?

It challenges the long-standing belief that the rectovaginal septum (RVS) is a common site of deep endometriosis.

How was the study conducted to assess the distribution of endometriosis?

It used a prospective observational design combining advanced ultrasound, meticulous keyhole surgery, and histopathological tissue analysis.

Where were the lesions found if not in the rectovaginal septum?

All detected lesions were located in surrounding structures, including the uterosacral ligaments, the rectouterine pouch, or the bowel.

Sep 30, 2026

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