A Long Road to Diagnosis: A Case with Unexpected Twists

Introduction: It is often thought that cases of obstructive acute kidney injury (AKI) are straightforward to diagnose and manage. The following case report explores how experienced physicians navigated an unusual case and the convoluted path taken to arrive at the eventual diagnosis. Case Description: A 74 year-old previously healthy male presented to the hospital with syncope in the context of six weeks of nausea, vomiting, anorexia and one year of nocturia. Labwork showed potassium of 8.1mmol/L and creatinine (Cr) of 14.97mg/dL (baseline of 1.07mg/dL). EKG showed peaked T-waves. After management of hyperkalemia, significant arrhythmias persisted so dialysis was initiated. A renal ultrasound showed bilateral hydronephrosis and ascites. Presuming prostactomegaly as the case of the obstruction, a foley catheter was placed and drained 445mL of urine, but he became oligoanuric. Urine microscopy showed one heme-granular cast. Urine albumin to creatinine ratio was 101mg/g. A serologic work-up was negative and kidney biopsy was consistent with acute tubular necrosis (ATN). However, a repeat ultrasound showed no improvement in bilateral hydronephrosis and ascites. A paracentesis revealed malignant cells on cytology. Discussions were held regarding pursuing a contrast-enhanced CT for work-up of malignancy. However, in the context of severe AKI, a shared decision was made to delay the CT as it can impede renal recovery. Serum tumor markers revealed elevated Ca19-9, CA125, and CEA. A colonoscopy showed two colonic masses. We obtained a contrast-enhanced CT as we felt the potential information we would gain outweighed the risks, which showed metastatic malignancy with retroperitoneal masses causing bilateral ureteric obstruction and hydronephrosis. Nephrostomy tubes were inserted and the patient experienced significant renal recovery. He was discharged with a Cr of 1.4 mg/dL (eGFR of 53mL/min/1.73m2). Discussion: From this case, we learned it is imperative to re-evaluate initial assumptions when an element of the case is unusual, such as why he became oligoanuric after a foley was placed if the obstruction was relieved and why he had new-onset ascites. Persistent anomalies prompted additional studies, which led to the uncovering of the previously unknown metastatic malignancy, the true cause of the patient's AKI. This case highlighted the dangers of early diagnostic closure and the importance of thorough investigation.