Bladder Endometriosis: A Rare Histopathological Entity Diagnosed by Transurethral Resection

A 28-year-old female presented to the urosurgery outpatient department with a 2-month history of recurrent fever, lower abdominal pain, dysuria with a burning sensation, and frequent per vaginal discharge. Notably, she reported intense, recurring pelvic pain but denied any history of hematuria, urgency, abnormal vaginal bleeding, weight loss, or anorexia. The patient, who had recently married in February 2025, noted the onset of symptoms shortly after her marriage and also complained of dyspareunia. Her menstrual cycles were regular, and there was no history of prior surgery or chronic medical conditions. Urine microscopy and culture were within normal limits. Ultrasonogram revealed moderate left-sided hydronephrosis with an ill-defined soft-tissue lesion on the left posterolateral bladder wall measuring 26 mm × 15 mm. The lesion extended to the left VUJ, contributing to hydronephrosis. A differential diagnosis of a mitotic etiology was considered. A contrast-enhanced computed tomography (CECT) urogram demonstrated left hydroureteronephrosis, with the lower end of the left ureter encased by a soft-tissue mass in the rectouterine space. There was also a suspected adherence to the anterior wall of the anal canal and a potential right tubo-ovarian lesion, raising suspicion for endometriosis. Given the discordance between the transabdominal ultrasonography and CECT findings, a transurethral resection of the bladder tumor was performed for definitive diagnosis. Intraoperative findings revealed stenosis and narrowing of the intramural portion of the left ureter, with a flat, sessile growth on the posterior wall near the left ureteric orifice. Histopathological examination revealed transitional (urothelial) epithelium lining the tissue fragments, with underlying fibrocollagenous and fibromuscular stroma containing endometrial glands and stroma [ Figures 1 and 2 ]. There was also a mixed inflammatory infiltrate, along with hemosiderin-laden macrophages and numerous congested blood vessels. Thus, a diagnosis of bladder endometriosis was rendered. Endometrial glands and stroma at low power (H and E, ×4 and ×10) Endometrial glands and stroma at high power (H and E, ×40) The patient was followed for approximately 6–8 months after diagnosis, during which she reported a gradual reduction in pain severity. Nonetheless, she continued to require intermittent analgesic therapy for episodic exacerbations. She was subsequently lost to follow-up.

Bladder endometriosis remains an uncommon clinical entity and can often pose significant diagnostic challenges due to its nonspecific symptoms. It is a rare form of deep infiltrating endometriosis (DIE), defined by the presence of ectopic endometrial glands and stroma within the bladder wall, often involving the detrusor muscle and adjacent layers.[ 1 2 3 ] Urinary tract endometriosis affects approximately 1%–2% of women with endometriosis, with bladder involvement accounting for 80%–90% of these cases, making bladder endometriosis itself a rare entity comprising <2% of all endometriosis diagnoses.[ 1 4 ] The most common sites of bladder endometriosis include the posterior and lateral bladder walls, especially near the vesicoureteric junction (VUJ), which was the location of the lesion in our case.[ 2 3 ] We report a rare case of endometriosis of the urinary bladder.

Bladder endometriosis, though rare, should be considered in young women presenting with nonspecific urinary and pelvic symptoms. Histopathological examination is crucial for distinguishing it from malignancies and other urological conditions. Early and accurate diagnosis through a multidisciplinary approach enables appropriate management, improving patient outcomes and preserving fertility. The authors certify that they have obtained all appropriate patient consent forms. In the form, the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed. There are no conflicts of interest.

Bladder endometriosis is a rare manifestation of DIE, characterized histologically by ectopic endometrial glands and stroma infiltrating the bladder wall, often with associated chronic inflammation.[ 1 3 ] It accounts for <2% of all endometriosis cases and represents the majority (80%–90%) of urinary tract endometriosis.[ 1 4 ] It predominantly affects women of reproductive age and typically involves the posterior and lateral walls of the bladder, especially near the VUJ, as seen in our patient.[ 2 3 ] Clinically, it presents with nonspecific symptoms such as pelvic pain, dysuria, frequency, urgency, dyspareunia, and occasionally hematuria, often mimicking urinary tract infections or malignancies.[ 2 3 ] These factors contribute to its frequent misdiagnosis and delayed identification. Radiological imaging is valuable in identifying mass lesions, but its specificity in diagnosing bladder endometriosis is limited. Transabdominal ultrasound, CECT, or magnetic resonance imaging may detect bladder wall thickening or soft-tissue lesions near the VUJ, but these findings can overlap with neoplastic conditions.[ 3 5 ] As observed in our case and in other reports, bladder endometriosis may closely resemble transitional cell carcinoma, underscoring the need for histological confirmation.[ 1 3 ] Histopathology remains the diagnostic cornerstone, revealing endometrial glands and stroma within the bladder wall, often accompanied by chronic inflammation and hemosiderin-laden macrophages.[ 1 3 ] Similar findings were reported in our case. The pathogenesis of bladder endometriosis is still under investigation. Theories include retrograde menstruation with implantation, lymphatic or hematogenous dissemination, and metaplasia of Müllerian remnants.[ 2 ] Recent literature also explores the roles of hormonal influence, immunological dysfunction, and genetic susceptibility in the disease’s progression and recurrence.[ 5 ] Management strategies are individualized based on the severity of symptoms, fertility desires, and lesion extent. Hormonal therapies – such as combined oral contraceptives, GnRH analogs, or progestins – are typically first-line treatments, particularly for pain control and suppression of disease activity.[ 2 5 ] However, surgical intervention becomes necessary in cases with obstructive uropathy, severe symptoms, or when malignancy cannot be excluded. Laparoscopic and robotic-assisted partial cystectomy is preferred for complete resection and symptom resolution in deeply infiltrative cases.[ 4 ] Importantly, recurrence after hormonal therapy discontinuation remains a concern. Studies show that surgical outcomes are generally favorable with low recurrence when complete excision is achieved.[ 4 5 ] However, awareness remains low, leading to delays in diagnosis that impact quality of life and, potentially, fertility.[ 2 6 ] Because of adverse effects and poor communication with medical professionals, women with endometriosis frequently express dissatisfaction with conventional treatments.[ 7 ] Swift et al . reported that greater public and clinician awareness is essential for earlier diagnosis, reduced morbidity, and improved productivity. Their findings also support evidence-based reproductive health care in the Eastern Mediterranean region and lay the groundwork for targeted studies on population-specific environmental and genetic contributors to disease risk and pelvic pain.[ 8 ]