Unilateral ureteral endometriosis masquerading as a ureteral tumor and resulting in complete loss of renal function: A case report.

Ureteral endometriosis is a rare manifestation of endometriosis that involves the infiltration of endometrial tissue into the ureters, leading to ureteral obstruction and potential renal dysfunction. However, its preoperative diagnosis is difficult. Herein, we report the case of a woman in her early 50s who presented with severe hydronephrosis of the right kidney, ureteral dilation, and suspicion of a ureteral tumor based on initial imaging studies. However, the pathological results after resection of the right kidney and right ureter revealed the presence of endometrial tissue in an ectopic location. This case highlights the importance of considering endometriosis as a differential diagnosis in cases of ureteral obstruction, even in atypical clinical scenarios, and emphasizes the need for prompt diagnosis and intervention to prevent irreversible renal damage and optimize patient outcomes.