Progression of hydronephrosis in end-stage renal disease as a potential indicator of underlying upper urinary tract tumors: a report of a rare case.

Upper tract urothelial carcinoma (UTUC) is a rare malignancy with a higher incidence in patients with end-stage renal disease (ESRD), particularly in regions with specific environmental risk factors. The diagnosis of UTUC in patients with ESRD remains challenging because of certain limitations inherent to current urine cytology techniques and imaging quality. Herein, we report the case of a 72-year-old woman with a history of bladder urothelial carcinoma and ESRD who was receiving regular hemodialysis and was incidentally diagnosed with high-grade multifocal UTUC following a nephrectomy procedure to treat symptomatic hydronephrosis. Despite routine cystoscopic surveillance and unremarkable cytological findings, progressive hydronephrosis was noted on serial imaging. Surgical intervention was performed as the patient's symptoms worsened progressively, after which pathological examination confirmed the presence of UTUC with renal parenchymal invasion. This case highlights the notion that UTUC should be considered as a differential diagnosis in patients with ESRD exhibiting symptomatic hydronephrosis of an unexplained etiology.