A CASE OF ACUTE KIDNEY INJURY WITH UNEXPLAINED OSMOTIC NEPHROSIS Roma Cruz, Ranil Gajanayaka, Panupong Lisawat , Glen Markowitz, Raymond Raut, Winston Shih. Danbury Hospital, Danbury, CT, USA Osmotic nephrosis is a pathologic term used to describe the pattern of vacuolization and swelling of the proximal renal tubular cells. This has been associated with infusion of sucrose, maltose, mannitol, dextran and iodinated contrast media. We report a case of osmotic nephrosis in a patient with no exposure to these agents. A 62 year old white female presented with 36 hour history of anuria. Her medical history is significant for hypertension and diabetes mellitus. Medications on admission included Valsartan, Hydrochlorothiazide, Metformin, Insulin,Simvastatin and Saxagliptin which was started 3 months before. On admission, physical exam was unremarkable. Initial laboratory exam revealed BUN 40 mg/dl, creatinine of 5.6 mg/dl, from a baseline of 1.3 mg/dl, 2 months prior. Both kidneys are of normal size and without hydronephrosis. Urinalysis revealed 3+ protein, 3+blood, 9-30 WBC. Complement levels, ANA, ANCA, hepatitis serologies and HIV were negative. Patient remained anuric, her serum creatinine peaked at 9.94 mg/ dL and she required 2 sessions of hemodialysis. A kidney biopsy was consistent with osmotic nephrosis. Patient spontaneously started diuresing on the 4 hospital day and was discharged a week later with a serum creatinine at its baseline 1 mg/dL. Cases of acute kidney injury and acute tubular necrosis have been reported with Sitagliptin (Januvia-another DPP4 inhibitor) and Exenatide(Byetta GLP-1 analog) and have been associated with rapid improvement once these medications were discontinued. Renal biopsies were performed in a minority of cases. This is, to our knowledge, the first case of AKI that occurred in the presence of Saxagliptin with no exposures that could explain the osmotic nephrosis.