A case of omental endometriosis complicated by hemorrhagic ascites leading to pelvic encapsulated effusion

Cao S, Shuo Cao, Tao Zhang, Zhang T
BMC women's health · 2026 · vol. 26(1) · doi:10.1186/s12905-026-04607-8 · PMID:42337492 · PMC13551812 · W7165676489
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⚙ AI-generated summary by gemini-2.5-flash-lite, 2026-07-09 ⓘ

This case report describes a rare instance of omental endometriosis causing hemorrhagic ascites and pelvic encapsulated effusion in a premenopausal woman, emphasizing its consideration in unexplained presentations.

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⚙ AI-generated deep summary by claude@2026-07, 2026-07-09 · read from full text ⓘ

This paper reports a clinical case of a 45-year-old premenopausal woman with increased menstrual flow and prolonged menstruation, who had no classic endometriosis symptoms or history of pelvic surgery or inflammatory disease but presented with hemorrhagic ascites, pelvic encapsulated effusion, and multiple omental nodules on CT. Serum testing showed mildly elevated CA125 with normal HE4, and ascitic cytology found no malignant cells; preoperative diagnosis of the cause of the hemorrhagic ascites was not definitive because findings overlapped with malignancy. Postoperative pathology and immunohistochemical results confirmed omental endometriosis, and the authors conclude that this rare extra-pelvic presentation can be considered even without typical symptoms or predisposing factors, noting the limitation that this is a single case. This paper is centrally about endometriosis — it describes a rare case of omental endometriosis presenting with hemorrhagic ascites and pelvic encapsulated effusion.

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Abstract

BACKGROUND: Endometriosis is an estrogen-dependent benign inflammatory disorder characterized by the implantation of active endometrial tissue (glands or stroma) outside the uterus, with pelvic adhesions as a core hallmark. Omental endometriosis is an extremely rare subtype of extra-pelvic endometriosis (accounting for < 5% of all extra-pelvic endometriosis cases), and its concurrent presentation with massive hemorrhagic ascites and de novo pelvic encapsulated effusion without predisposing factors (e.g., pelvic surgery, pelvic inflammatory disease) remains scarcely reported in existing clinical literature. CASE PRESENTATION: A 45-year-old premenopausal woman (gravida 4, para 2) presented with the chief complaint of increased menstrual flow and prolonged menstruation, without classic endometriosis symptoms such as dysmenorrhea or chronic pelvic pain and no history of abdominal/pelvic surgery or pelvic inflammatory disease. Examination revealed a significant amount of hemorrhagic ascites, pelvic encapsulated effusion, multiple omental nodules on abdominal CT, mildly elevated serum CA125 (85.51 IU/ml) with normal HE4 (61.22 pmol/L), and no malignant cells in ascitic cytology. The cause of hemorrhagic ascites was not definitively diagnosed preoperatively due to overlapping clinical and imaging features with malignant tumors; postoperative pathological and immunohistochemical findings confirmed omental endometriosis. CONCLUSION: Omental endometriosis should be considered in premenopausal women presenting with unexplained hemorrhagic ascites and pelvic encapsulated effusion, even in the absence of classic endometriosis symptoms, prior pelvic surgery, or malignant cytology-particularly when serum CA125 is elevated but HE4 remains normal. This case broadens the recognized clinical spectrum of extra-pelvic endometriosis and highlights the value of comprehensive preoperative evaluation combined with individualized, fertility-sparing surgical management.
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Abstract

Background Endometriosis is an estrogen-dependent benign inflammatory disorder characterized by the implantation of active endometrial tissue (glands or stroma) outside the uterus, with pelvic adhesions as a core hallmark. Omental endometriosis is an extremely rare subtype of extra-pelvic endometriosis (accounting for < 5% of all extra-pelvic endometriosis cases), and its concurrent presentation with massive hemorrhagic ascites and de novo pelvic encapsulated effusion without predisposing factors (e.g., pelvic surgery, pelvic inflammatory disease) remains scarcely reported in existing clinical literature. Case presentation A 45-year-old premenopausal woman (gravida 4, para 2) presented with the chief complaint of increased menstrual flow and prolonged menstruation, without classic endometriosis symptoms such as dysmenorrhea or chronic pelvic pain and no history of abdominal/pelvic surgery or pelvic inflammatory disease. Examination revealed a significant amount of hemorrhagic ascites, pelvic encapsulated effusion, multiple omental nodules on abdominal CT, mildly elevated serum CA125 (85.51 IU/ml) with normal HE4 (61.22 pmol/L), and no malignant cells in ascitic cytology. The cause of hemorrhagic ascites was not definitively diagnosed preoperatively due to overlapping clinical and imaging features with malignant tumors; postoperative pathological and immunohistochemical findings confirmed omental endometriosis.

Conclusion

Omental endometriosis should be considered in premenopausal women presenting with unexplained hemorrhagic ascites and pelvic encapsulated effusion, even in the absence of classic endometriosis symptoms, prior pelvic surgery, or malignant cytology—particularly when serum CA125 is elevated but HE4 remains normal. This case broadens the recognized clinical spectrum of extra-pelvic endometriosis and highlights the value of comprehensive preoperative evaluation combined with individualized, fertility-sparing surgical management. Similar content being viewed by others

Acknowledgements

Written consent for publication was obtained from the patient. Funding None. Author information Authors and Affiliations Corresponding author Ethics declarations Ethics approval and consent to participate The study was approved by the Institutional Review Board at the Baoding No.1 Central Hospital. Participant gave written consent to participate in the study. Consent for publication Written informed consent for publication of clinical details and/or clinical images was obtained from the participant. A copy of the consent form is available for review by the Editor of the journal. Competing interests The authors declare no competing interests. Additional information Publisher’s note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations. Rights and permissions Open Access This article is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License, which permits any non-commercial use, sharing, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if you modified the licensed material. You do not have permission under this licence to share adapted material derived from this article or parts of it. The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by-nc-nd/4.0/. About this article Cite this article Cao, S., Zhang, T. A case of omental endometriosis complicated by hemorrhagic ascites leading to pelvic encapsulated effusion. BMC Women's Health (2026). https://doi.org/10.1186/s12905-026-04607-8 Received: Accepted: Published: DOI: https://doi.org/10.1186/s12905-026-04607-8

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MeSH descriptors

Ascites Ascites Ascites Ascites Ascites Ascites Ascites Ascites Ascites Ascites Ascites Ascites Ascites Ascites Ascites Ascites Ascites Ascites Ascites Ascites

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chemicals 1
estrogen

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