Abstract: SA-PO0069
Leveraging Cystatin C to Identify Pseudo-AKI from Urinary Ascites
Session Information
- AKI: Clinical Diagnostics and Biomarkers
November 08, 2025 | Location: Exhibit Hall, Convention Center
Abstract Time: 10:00 AM - 12:00 PM
Category: Acute Kidney Injury
- 102 AKI: Clinical, Outcomes, and Trials
Authors
- Nguyen, Julia, Walter Reed National Military Medical Center, Bethesda, Maryland, United States
- Yuan, Christina M., Walter Reed National Military Medical Center, Bethesda, Maryland, United States
- Nee, Robert, Walter Reed National Military Medical Center, Bethesda, Maryland, United States
Introduction
Patients with urinary ascites often present with abdominal discomfort, oliguria with apparent AKI, but without intrinsic renal disease. Due to its rarity, diagnosis may be delayed. Failure to recognize urinary leak/ascites can lead to unnecessary intervention, such as dialysis initiation, for this pseudo-AKI.
Case Description
A man with newly diagnosed prostate cancer and stage 3 chronic kidney disease, baseline estimated glomerular filtration rate (eGFR) 55 mL/min/1.73m2, presented with suprapubic pain and oliguria one week after undergoing a robotic radical prostatectomy. On physical examination, he had diffuse abdominal tenderness. Admission labs: serum sodium 116 mEq/L, potassium 6.4 mEq/L, HCO3 15 mEq/L, BUN 90.4 mg/dL, creatinine (Cr) 10.1 mg/dL, and cystatin C eGFR 56 mL/min/1.73m2. CT scan demonstrated a large amount of intra- and extraperitoneal fluid, consistent with postoperative urine extravasation. He required evacuation of intraperitoneal fluid with catheter placement. Drained ascitic fluid: sodium 32 mEq/L, potassium 23 mEq/L, chloride <20 mEq/L and creatinine 104 mg/dL. Ascites: serum Cr ratio was 7.89. He underwent surgical repair of the anastomotic leak along with Foley drainage. Over the next 4 days, serum Cr returned to baseline with resolution of electrolyte derangements.
Discussion
Intraperitoneal urine extravasation results in systemic resorption of electrolytes and other biochemical moieties in a process analogous to peritoneal dialysis, but in reverse, leading to a pseudo-AKI pattern. This is characterized by hyponatremia, hyperkalemia, elevated BUN and Cr, while ascitic fluid exhibits the same chemical content as urine to include low sodium, chloride, and elevated Cr. An ascites: serum Cr ratio >1.0 is highly suggestive of an intraperitoneal urine leak. There is no established method to estimate intrinsic renal function in this setting, posing a challenge for medical management and drug dosing. We monitored cystatin C levels, which is minimally excreted in the urine and less permeable across the peritoneal membrane, thus rendering greater utility in estimating true GFR compared to serum Cr.
The views expressed in this abstract are those of the author(s) and do not necessarily reflect the official policy of the Department of Defense or the United States Government.