Acute Oxalate Nephropathy Associated with Orlistat: A Case Report with a Review of the Literature

Orlistat is a gastrointestinal lipase inhibitor used for weight reduction in obese individuals. Enteric hyperoxaluria caused by orlistat leads to oxalate absorption. Acute oxalate nephropathy is a rare complication of treatment with orlistat. Herein we report a patient presenting with acute renal failure which improved minimal with intravenous hydration. She was found to have oxalate crystals on renal biopsy. Patient admitted orlistat use over the counter for weight reduction on further questioning. The purpose of this case review is to increase awareness among patients since they are more focused on losing weight. This case also calls for the provider attention to educate patients regarding side effects of orlistat because of easy availability of orlistat over the counter. 1. Introduction Orlistat, a gastrointestinal lipase inhibitor, is used for weight reduction in obese patients with BMI？>？30？kg/m2 and BMI？>？28？kg/m2 with associated risk factors such as diabetes mellitus hypertension. The majority of the side effects associated with orlistat involve gastrointestinal tract. The rare but serious adverse effect of orlistat treatment is acute oxalate nephropathy caused by increased fat malabsorption. It is diagnosed by evidence of oxalate crystals in renal biopsy specimen under polarized light. We report a case of obese patient consuming orlistat for weight reduction presented with acute oxalate nephropathy manifesting as acute renal failure. 2. Case A 56-year-old woman presented with fatigue to her primary doctor. She was sent to the hospital for acute kidney injury with a serum creatinine (Cr) of 6.6？mg/dL as compared to Cr of 0.9？mg/dL 1 year ago. The patient also had anemia with a hemoglobin of 7.4？g/dL. She denied having any previous medical problems but reported having intentionally lost 70？lbs over the last 18 months. She denied the use of any regular medications during her hospitalization and denied the use of nonsteroidal anti-inflammatory drugs (NSAIDs). Her physical examination was unremarkable. A urinalysis performed at admission was negative for urinary protein or eosinophils, with 2–5？WBCs per high powered field (hpf) and 0–2？RBCs/hpf, hemoglobin 7.4. The rest of complete blood count and basic metabolic panel was within normal limits. A renal ultrasound suggests medullary nephrocalcinosis. Her serum Cr improved with intravenous hydration to 5.7？mg/dL. She did not require hemodialysis and further clinical follow-up was performed on an outpatient basis. Her renal function failed to improve significantly over the next three months, which