Urate nephropathy following chronic ileostomy acidosis

Normal renal function and normal urinalysis results in an 81-year-old man deteriorated over a 6-month period following an ileostomy, associated with metabolic acidosis, persistent aciduria, proteinuria, and a urinary sediment that showed numerous red blood cells, granular casts, and 'reactive' epithelial cells with intracellular uric acid (UA) crystals. These also formed extensive UA casts. Oral sodium bicarbonate therapy completely reversed all of the abnormalities. Renal biopsy, while it failed to demonstrate significant tubular obstruction, showed evidence of extensive epithelial cell injury. It is suggested that intestinal losses of bicarbonate resulted in persistent excretion of an acidic urine which promoted UA crystal formation within renal tubules and in epithelial cells which then caused cellular injury and the release of cytokines, leading to an altered regulation of the renal blood flow. The importance of microscopic techniques in the diagnosis is stressed along with the significance for managing both acute and chronic renal failure.