同步膀胱與輸尿管腫瘤與困難診斷之完全型雙套集尿系統：個案報告

徐振益、歐弦哲、陳浩瑋、盧嘉文、阮雍順、陳妤甄

高雄醫學大學附設中和紀念醫院 泌尿部 泌尿科

A Hidden Duplex Collecting System Masked by Bladder Tumor Leading to Missed Upper Tract Urothelial Carcinoma: From Negative Ureteroscopy to pT3 Disease

Cheng-Yi Hsu、Hsien-Che Ou、Hao-Wei Chen、Kevin Lu、Yung-Shun Juan、Yu-Chen Chen

Department of Urology, Kaohsiung Medical University Hospital, Kaohsiung, Taiwan.

Background:

Duplex collecting system (DCS) is a common congenital anomaly, affecting approximately 1–2% of the population, with a female predominance. Although often asymptomatic, it may complicate the evaluation of upper urinary tract pathology. In rare instances, coexisting bladder tumors may obscure duplicated ureteral orifices, leading to delayed or missed diagnosis of upper tract urothelial carcinoma (UTUC).

Case Presentation:

An 80-year-old woman presented with several months of intermittent left flank pain. Contrast-enhanced computed tomography (CT) revealed left hydronephrosis and a suspicious lesion in the upper ureter (Figure A). Laboratory evaluation was notable for microscopic hematuria.

 Left ureteroscopy (URS) was arranged. During cystoscopy, only a single left ureteral orifice was identified. A cauliflower-like bladder tumor was found immediately adjacent to the orifice (Figure B). Transurethral resection of bladder tumor (TURBT) was performed, though complete hemostasis was challenging due to its proximity to the ureteral orifice. Pathology confirmed high-grade Ta urothelial carcinoma.

 Concurrent URS revealed no obvious ureteral mass or significant hydronephrosis but we still insert left double J, findings that were discordant with preoperative imaging. Given this inconsistency, a detailed re-evaluation of CT images was performed, revealing asymmetric hydronephrosis and delayed contrast excretion between renal moieties, suggestive of a duplex collecting system (DCS) (Figure C). It was hypothesized that the bladder tumor had obscured one of the duplicated ureteral orifices.

 A second-look URS performed four weeks later clearly demonstrated two distinct left ureteral orifices. Ureteroscopic evaluation identified tumor lesions arising from the ureter draining the lower moiety, confirming UTUC.

 The patient subsequently underwent robotic nephroureterectomy with bladder cuff excision (NUx+BCE). Final pathology revealed high-grade urothelial carcinoma, stage pT3.

Conclusion:

This case illustrates a critical diagnostic pitfall in which a bladder tumor adjacent to the ureteral orifice masked a duplicated ureter, resulting in an initially negative ureteroscopic evaluation and delayed diagnosis of advanced UTUC. When imaging and endoscopic findings are incongruent, clinicians should consider anatomical variants such as DCS and perform meticulous image re-evaluation. Early recognition is essential to avoid disease progression.

Keywords:

Duplex collecting system, upper tract urothelial carcinoma, ureteroscopy, nephroureterectomy, diagnostic pitfall