Patients at high risk for upper tract urothelial cancer: evaluation of hydronephrosis using high resolution magnetic resonance urography

PURPOSE: We assessed the potential of magnetic resonance urography (MRU) in the evaluation of hydronephrosis not explained by standard investigation in patients at high risk for upper tract urothelial cancer. MATERIALS AND METHODS: A total of 23 consecutive patients in a specialist urological unit with unexplained hydronephrosis prospectively underwent MRU which comprised overview heavily T2-weighted MR urographic images followed by focused high resolution turbo spin echo T2-weighted sequences obtained in an axial and coronal oblique plane through the level of urinary obstruction. All were at high risk for urothelial cancer and had either contraindications to or problems with standard investigations including poor contrast excretion due to obstruction or renal failure, failed ureteral cannulation or contrast allergy. Clinical events and imaging followup, subsequent endoscopic/surgical findings and histopathology validated MR findings. RESULTS: In 23 patients with a high clinical suspicion of upper tract transitional cell tumors (TCC), 8 ureteral and 5 renal pelvic TCCs (2 bilateral) were diagnosed by MR, and confirmed histologically. In a further 5 patients benign causes for the hydronephrosis were found. No intrinsic or extrinsic pathology was demonstrable in 5 patients whose imaging findings were stable during 1 year of followup. CONCLUSIONS: MRU is a valuable noninvasive investigation for evaluating hydronephrosis in this group of patients with suspected urothelial cancer in which routine investigation had failed to provide clinically important information. Focused high resolution T2-weighted images were reliable in the diagnosis of ureteral and renal pelvic TCCs, and were valuable in excluding these and other mass lesions as the cause of hydronephrosis.