腎移植病人於原位腎切除術後持續存在高惡性度尿路上皮癌：病例報告

呂孟軒¹、謝佐宜^1,2

¹中山醫學大學附設醫院 泌尿科；²中山醫學大學 醫學系

Persistent High-Grade Urothelial Carcinoma after Native Nephroureterectomy in a Transplant Recipient: A Case Report

Meng-Hsuan Lu¹, Tzuo-Yi Hsieh^1,2

¹Department of Urology, Chung Shan Medical University Hospital;

²School of Medicine, Chung Shan Medical University

Introduction: Renal transplant recipients (RTRs) face heightened urological malignancy risks due to immunosuppression. When positive cytology persists despite negative bladder findings, localizing the tumor between atrophic native kidneys and the allograft is challenging. While native kidneys are statistically more likely, anatomical displacement of the transplanted ureter often precludes retrograde evaluation, creating a diagnostic dilemma when imaging is inconclusive and endoscopic access is restricted.

Case Presentation: A 70-year-old male with ESRD secondary to FSGS underwent deceased donor renal transplantation in 2017. His course was complicated by BK virus nephropathy and chronic interstitial fibrosis. Within the past year, he presented with hematuria and malignant cytology (PHGUC). Cystoscopy showed no bladder tumors, but the graft orifice's location on the anterior bladder wall near the bladder neck precluded retrograde flexible ureteroscopy. Computed tomography demonstrated atrophic native kidneys but no definitive tumor in either the native or transplanted organs. Based on the statistical likelihood of native malignancy and the non-functional status of the atrophic kidneys, the patient underwent robotic-assisted bilateral native nephroureterectomy. However, surgical pathology showed no malignancy. Postoperatively, persistent PHGUC shifted clinical suspicion toward the allograft as the probable source.

Discussion: In clinical practice, localizing malignancy in RTRs is primarily guided by epidemiological data indicating a higher probability of native kidney UC over the allograft. Despite inconclusive imaging, the decision to prioritize native organ removal was based on these statistics and the non-functional status of the native kidneys. However, persistent PHGUC post-nephroureterectomy strongly suggests a rare allograft primary. The diagnosis was further complicated by BK virus infection, which contributes to oncogenesis by inactivating tumor suppressors and activating mutagenic enzymes like APOBEC. The failure of retrograde access underscores the limitations of standard endoscopic surveillance when graft anatomy is displaced.

Conclusion: While native kidneys are statistically likely sources of malignancy, clinical suspicion must shift to the allograft when cytology remains positive despite negative native pathology and imaging. If the graft orifice is anatomically inaccessible for retrograde flexible ureteroscopy, clinicians should consider an earlier transition to antegrade techniques, such as percutaneous nephrostomy-guided selective cytology. This proactive approach facilitates timely diagnosis of allograft malignancies while potentially avoiding unnecessary native organ surgery.