The Kidneys Went Nuts: Oxalate Nephropathy From Excessive Cashew Nut Consumption

A 78-year-old man who had stable chronic kidney disease presented with marked elevation in his serum creatinine of 6.0 mg/dL compared with his baseline 2.05 mg/dL. His presenting history, vitals, and physical examination did not allude to a prerenal cause for acute kidney injury. His urinalysis was unremarkable with no evidence of white cell or red cell casts, no evidence of obstructive uropathy, negative serologies for autoimmune and viral etiologies, and negative for antineutrophil cytoplasmic antibody and antiglomerular basement membrane. Although his urinalysis was unremarkable, urine eosinophil was positive. He underwent a kidney biopsy, which showed acute tubular injury associated with extensive calcium oxalate crystal deposition. On revisiting his history, it was discovered that the patient had been consuming 3-4 oz of cashew nuts daily for the last 1 year. This is an uncommon case and highlights the need for heightened awareness of the dietary implications in patients with chronic kidney disease and the need for adequate counseling and intervention.