The Challenges of Diagnosing Nondilated Obstructive Uropathy: A Case Report.

Rationale: Nondilated obstructive uropathy (NDOU) is a rare cause of acute renal failure reported in less than 5% of cases of obstructive uropathy. It is typically associated with intrapelvic malignancies and diseases causing retroperitoneal lymphadenopathy and retroperitoneal fibrosis. As these conditions may prevent radiographic dilation of the collecting system, the diagnosis of NDOU may be missed by usual diagnostic testing. Presenting concerns of the patient: We present a case of acute anuric renal failure in a middle-aged woman with metastatic breast cancer associated with abdominal and retroperitoneal lymphadenopathy. Acute kidney injury was initially deemed secondary to drug-induced acute tubular necrosis (ATN) from bisphosphonate; however, there remained a high clinical suspicion of NDOU due to the presence of enlarged retroperitoneal lymph nodes on CT abdomen and pelvis with concerns for encasement of bilateral renal pelvic regions and ureters. Diagnoses: The patient underwent a retrograde pyelogram which demonstrated questionable narrowing bilaterally at the level of the renal pelvices. This led to an even stronger clinical suspicion of NDOU and urology service was consulted for evaluation. Intervention: Bilateral ureteral stents were placed by urology which led to robust urine output and rapid reversal of renal failure over the next 24 to 48 hours. Outcomes: Despite 2 weeks of anuria and hemodialysis, this patient's creatinine came back to her baseline. She was able to discontinue hemodialysis and her creatinine stabilized at 88.4 μmol/L (1 mg/dL). Teaching points: Nondilated obstructive uropathy is rare but important diagnosis that requires a high clinical suspicion in the appropriate clinical scenario. The lack of dilatation is believed to be related to encasement of the collecting system by tumor, fibrosis, or as in our case metastatic retroperitoneal lymphadenopathy. As this diagnosis cannot be overlooked, aggressive direct visualization or even intervention with internal or external stenting may be required to both diagnose and treat this condition.