Right hydronephrosis due to asymptomatic ureteral endometriosis: A case report

a Department of Ultrasound, First Affiliated Hospital of China Medical University, Shenyang, China. Received: 18 August 2025 / Received in final form: 15 October 2025 / Accepted: 5 November 2025 Written informed consent was obtained from the patient for publication of this case report and any accompanying images. A copy of the written consent is available for review by the Editor-in-Chief of this journal. The authors have no funding and conflicts of interest to disclose. The datasets generated during and/or analyzed during the current study are available from the corresponding author on reasonable request. How to cite this article: Cao X-T, Wan W-N, Yang G-C. Right hydronephrosis due to asymptomatic ureteral endometriosis: A case report. Med Case Rep Study Protoc 2025;6:6(e00392). *Correspondence: Wei-Na Wan, Department of Ultrasound, First Affiliated Hospital of China Medical University, Shenyang, Liaoning 110001, China (e-mail: [email protected]). This is an open access article distributed under the Creative Commons Attribution License 4.0 (CCBY), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Endometriosis involves uterine glands and endometrial tissue outside the uterus, with ureteral invasion being rare and often asymptomatic. Accurate diagnosis relies on multimodal ultrasound (abdominal, transvaginal, and contrast-enhanced) and ultrasound-guided transvaginal posterior puncture biopsy. Patient concerns: A 40-year-old premenopausal female was admitted for elevated blood pressure, with no urologic symptoms. Diagnoses: Abdominal computed tomography indicated right hydronephrosis and a right distal ureteral occupying lesion. Combined abdominal-transvaginal ultrasound, contrast-enhanced ultrasound, and biopsy confirmed ureteral endometriosis. Interventions: Multimodal ultrasound (abdominal, transvaginal, and contrast-enhanced) and ultrasound-guided transvaginal posterior puncture biopsy were performed for diagnosis. Outcomes: Rapid and definitive diagnosis was achieved, enabling timely intervention to prevent disease progression. Lessons: For premenopausal women with asymptomatic hydronephrosis and ureteral stenosis, general ultrasound combined with contrast-enhanced ultrasound and biopsy allows rapid, definitive diagnosis, preventing disease progression. Plain Language SummaryEndometriosis can sometimes affect the ureters, but this is rare and often without symptoms. A 40-year-old woman was found to have high blood pressure and right hydronephrosis, but no urinary symptoms. Using a combination of abdominal and transvaginal ultrasounds, along with a biopsy, doctors diagnosed her with ureteral endometriosis. This approach allowed for a quick and accurate diagnosis, which is crucial for timely treatment to prevent further complications. The study suggests that for women with asymptomatic hydronephrosis and ureteral stenosis, using these diagnostic methods can effectively identify ureteral endometriosis. Text is machine generated and may contain inaccuracies. FAQ 1. Introduction Endometriosis is defined as the presence of functional uterine glands and endometrial tissue outside the uterine cavity. The disease is characterized by significant local invasiveness and typically requires hormonal or surgical treatment.[1] The typical clinical manifestations of endometriosis include dysmenorrhea, infertility, and lower abdominal pain associated with the menstrual cycle; however, most cases of extragenital endometriosis are misdiagnosed, often because patients do not present to a gynecology clinic.[2] Endometriosis can be categorized into three types: superficial endometriosis, ovarian endometriosis, and deep infiltrating endometriosis (DIE). DIE can involve the uterosacral ligaments, the rectovaginal space, and intraperitoneal organs such as the intestines and urinary tract.[3] Approximately 1% of pelvic endometriosis cases involve the urinary tract, with the bladder being the most commonly affected site; ureteral endometriosis accounts for approximately 0.08% to 1% of all endometriosis cases.[4] The incidence of asymptomatic renal function loss due to ureteral endometriosis is as high as 25% to 43%.[5] We present a case of a patient with right hydronephrosis and ureteral stenosis who was diagnosed with ureteral endometriosis following a 5-month diagnosis and treatment process. 2. Case presentation A 40-year-old married female patient was admitted to the hospital for examination due to experiencing palpitations and elevated blood pressure. During her stay, she was found to have abnormal renal function and increased urinary protein levels. She therefore underwent urological examinations, which revealed right-sided hydronephrosis. The patient had no lower urinary tract symptoms, such as urinary frequency (abnormally increased urination episodes), urgency, or hematuria. Computed tomography urography (CTU) revealed dilation of the right upper ureter with hydronephrosis, narrowing of the ureteral lumen at the pelvic segment, and reduced enhancement of the right kidney. The patient then underwent right ureteral stenting. A follow-up CTU (Fig. 1) showed soft tissue density shadows adjacent to the distal right ureter, associated ureteral involvement, and right-sided hydronephrosis (Fig. 1). Based on the imaging findings, the space-occupying lesion was considered extraureteral; therefore, the patient was referred to the gynecology department for evaluation of potential gynecological etiologies. Gynecological examinations revealed human papillomavirus positivity, and cervical liquid-based thin-layer cytology showed atypical squamous cells of undetermined significance. To clarify the nature of the cervical lesion, a further cervical biopsy was performed, and the pathological result indicated a high-grade squamous intraepithelial lesion. Combining the patient’s medical history, imaging findings, and pathological results, it was initially determined that compression of the ureter by the right pelvic wall mass was the primary cause of right hydronephrosis and ureteral stenosis. To further confirm the nature of the cervical lesion and rule out cervical cancer metastasis, the patient underwent a cervical loop electrosurgical excision procedure. Postoperative pathology revealed cervical intraepithelial neoplasia grade I with negative margins, thereby ruling out invasive cervical cancer and the possibility of metastasis. Combined abdominal and transvaginal ultrasound scanning: an irregular hypoechoic lesion was seen to the right of the uterine isthmus (adjacent to the uterine cervix) (Fig. 2). Contrast-enhanced ultrasound (CEUS) and ultrasound-guided transvaginal posterior puncture biopsy were performed. For CEUS, the second-generation contrast agent SonoVue® (Bracco S.p.A., Milan, Italy) was used. The patient was placed in the lithotomy position, and the CEUS mode of the ultrasound system (model: Mindray Neuwa R9 Exp) was activated. Timing was initiated at the start of injection, and real-time dynamic imaging was performed for approximately 2 minutes. The hypoechoic lesion located to the right of the uterine isthmus (adjacent to the uterine cervix) showed weak, heterogeneous hypoenhancement: initial focal enhancement in the arterial phase (~15–30 seconds after injection, Fig. 3) and slightly expanded but persistent hypoenhancement in the venous phase (~31–60 seconds after injection, Fig. 4). The pathological analysis of the biopsy sample showed uterine gland tissue (Fig. 5); when combined with immunohistochemical findings, the results were consistent with endometriosis. The patient was instructed to take oral dienogest for 1 month, followed by a transvaginal ultrasound reexamination. One month later, the follow-up ultrasound showed that the size of the endometriotic lesion had not increased, so dienogest treatment was continued. Half a year after the percutaneous placement of the right ureteral double-J stent, the ureteral stent was replaced. After the stent replacement, the patient was advised to undergo regular transvaginal ultrasound reexaminations every 3 months. These follow-ups aim to monitor 2 key aspects: first, the dynamic changes in the size of the endometriotic lesion to evaluate the long-term efficacy of dienogest; second, the patency of the ureteral stent and the improvement of right-sided hydronephrosis, so as to timely detect potential complications such as stent obstruction or displacement. Correlative imaging of the right paraureteral lesion and right hydronephrosis. Left image: Axial view of CTU with intravenous contrast. Yellow arrow indicates a hypodense (low-density) lesion adjacent to the distal right ureter, which shows no obvious enhancement after contrast injection. Blue arrow indicates the uterus (anatomical reference). Right image: Longitudinal transabdominal ultrasound image of the right kidney. The white arrow indicates the separated renal collecting system, with a measured width of approximately 1.1 cm – consistent with mild-to-moderate hydronephrosis. This image is published with the patient’s written informed consent. CTU = computed tomography urography. Transvaginal ultrasound image with color Doppler of the pelvic region. A: White arrow indicates a right-sided hypoechoic deep infiltrating endometriosis lesion; B: Yellow arrow indicates a left-sided hypoechoic soft tissue focus. Key clarifications: (1) The left-sided anechoic (black) triangular area is part of the DIE focus; (2) Color Doppler was used to evaluate lesion vascularity, ruling out hypervascular malignancies early. This image is published with the patient’s written informed consent. DIE = deep infiltrating endometriosis. CEUS arterial phase image of the right paraureteral lesion. This image was acquired ~15 to 30 seconds after intravenous injection of SonoVue®. Yellow regions represent enhanced tissues, and black regions represent non-enhanced tissues. The right paraureteral lesion shows initial, focal weak yellow enhancement (peripheral perfusion only) with a black non-enhanced center, consistent with the “slow enhancement, hypoenhancement” feature of endometriosis. This image is published with the patient’s written informed consent. CEUS = contrast-enhanced ultrasound. CEUS venous phase image of the right paraureteral lesion. This image was acquired ~31 to 60 seconds after intravenous injection of SonoVue®. Yellow regions represent enhanced tissues, and black regions represent non-enhanced tissues. Compared to the arterial phase, the right paraureteral lesion’s yellow enhanced area expands slightly (diffuse perfusion) but remains weakly enhanced (lighter yellow than adjacent normal tissue); the central black non-enhanced area shrinks but persists. This persistent hypoenhancement confirms the benign nature of the lesion. This image is published with the patient’s written informed consent. CEUS = contrast-enhanced ultrasound. Pathological image of the lesion associated with right ureteral endometriosis. The pathological examination of the lesion that appeared hypoechoic on ultrasound (located outside the uterus, adjacent to the right uterine isthmus and distal right ureter) revealed ectopic uterine glandular tissue – confirming the diagnosis of endometriosis. The section was stained with hematoxylin-eosin (HE) and imaged at a light microscopic magnification of 40×. This image is published with the patient’s written informed consent. 3. Discussion In urinary endometriosis, the bladder is most frequently involved, followed by the ureters and kidneys in a ratio of 40:5:1.[6] Ureteral endometriosis can be classified into 2 subtypes: approximately 20% are endogenous, and 80% are exogenous.[7] The left ureter is more commonly affected than the right; nearly half of patients with ureteral endometriosis are asymptomatic, which may lead to misdiagnosis and irreversible renal failure.[8] The left ureter’s higher susceptibility is attributed to 2 factors: anatomical proximity to common endometriotic foci (e.g., left uterosacral ligament, rectovaginal septum), which increases exposure to compressing or invading lesions; and peritoneal fluid’s natural flow toward the left pelvic cul-de-sac, facilitating ectopic endometrial cell implantation near the left ureter. In our patient, the right ureteral involvement likely resulted from an atypical implantation of endometriotic lesions in the right pelvic sidewall, as confirmed by imaging and biopsy. Transvaginal ultrasound is the first-line tool for diagnosing DIE, which is characterized by hypoechoic or isoechoic solid nodules with smooth or irregular contours. When combined with transabdominal ultrasound, it can also detect the presence of peritoneal or ovarian implants and identify urinary system lesions such as hydronephrosis.[9] CEUS involves injecting a contrast agent into blood vessels to visualize the microcirculation of lesions and can be applied to many vital organs of the human body.[10] Beyond pelvic imaging, CEUS has broad applications in evaluating vital organs: For the pancreas, it differentiates pancreatic cancer from autoimmune pancreatitis by comparing lesion enhancement with normal pancreatic parenchyma across 3 phases (arterial: 0–30 seconds; pancreatic: 31–60 seconds; delayed: 61–120 seconds). For the liver, it distinguishes benign (e.g., hemangiomas) and malignant (e.g., hepatocellular carcinoma) lesions via dual blood supply-related enhancement patterns. For the omentum, it identifies malignant lesions (e.g., metastases) by their hyperenhancement versus benign lesions (e.g., inflammation) with hypoenhancement. This versatility supports CEUS as a valuable tool for lesion characterization across multiple organ systems. It has been widely used in the diagnosis of ovarian endometriotic cysts, adenomyosis, and abdominal wall endometriosis.[11] Ureteral malignant tumors tend to exhibit high enhancement during the arterial phase of contrast imaging (10–30 seconds after contrast agent administration), whereas most benign lesions – including those caused by chronic infection or ureteral endometriosis – show low enhancement or mild isoechogenic enhancement.[12] For CEUS, a low enhancement pattern in the arterial phase may indicate a relatively poor blood supply to DIE lesions. Meanwhile, the small subset of cases displaying high enhancement might be associated with reactive inflammation in the muscularis propria and surrounding tissues infiltrated by DIE lesions.[11] Our case also confirms that ureteral endometriosis exhibits low enhancement in the arterial phase on CEUS. CEUS was selected as a key imaging modality for evaluating the distal ureteral lesion, despite similar visualization rates of the entire ureter between CEUS (50%) and fluoroscopy (53.3%).[10] This choice was driven by our core diagnostic goal – characterizing the nature of the extraureteral lesion compressing the distal ureter – for which CEUS offered unique advantages over fluoroscopy: CEUS assesses lesion vascularity: the lesion’s weak, heterogeneous hypovascularity on CEUS supported a benign etiology and ruled out hypervascular malignancies. And CEUS provides real-time dynamic imaging: even with partial distal ureter visualization, we confirmed the lesion’s intimate association with the distal ureter. Additionally, CEUS avoided ionizing radiation and enabled concurrent ultrasound-guided biopsy. Thus, while CEUS and fluoroscopy have comparable entire ureter visualization rates, CEUS was superior for our specific diagnostic needs, aligning with its utility for pelvic lesion characterization in endometriosis-related ureteral obstruction.[10,11] CTU has high accuracy in detecting upper urinary tract malignant tumors; in some cases where CTU findings are inconclusive, the diagnosis can be confirmed via CEUS examination[12] Therefore, CEUS holds great significance for the diagnosis of urogenital endometriosis. 4. Conclusion Ureteral endometriosis is rare, and some patients present with no urinary symptoms – this can eventually lead to serious complications such as hydronephrosis and ureteral stenosis. Combining conventional ultrasound with CEUS and ultrasound-guided transvaginal posterior puncture biopsy may serve as a minimally invasive, rapid, and definitive diagnostic method. Acknowledgments Thanks to the department leaders and teachers for their help and guidance, the department for providing equipment and data, and the anonymous reviewers for their constructive comments. Author contributions Data curation: Guo-Chun Yang. Writing – original draft: Xi-Tong Cao. Writing – review & editing: Wei-Na Wan. Abbreviations: CEUS contrast-enhanced ultrasound CTU computed tomography urography DIE deep infiltrating endometriosis TVS transvaginal ultrasound References [1]. Antonelli A, Simeone C, Zani D, et al. Clinical aspects and surgical treatment of urinary tract endometriosis: our experience with 31 cases. Eur Urol. 2006;49:1093–7; discussion 1097. [5]. Watanabe Y, Ozawa H, Uematsu K, Kawasaki K, Nishi H, Kobashi Y. Hydronephrosis due to ureteral endometriosis treated by transperitoneal laparoscopic ureterolysis. Int J Urol. 2004;11:560–2. [7]. Ponticelli C, Graziani G, Montanari E. Ureteral endometriosis: a rare and underdiagnosed cause of kidney dysfunction. 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