Impaired potassium and magnesium homeostasis in acute tubulo-interstitial nephritis.

Although acute tubulo-interstitial nephritis is increasingly recognized as a cause of acute renal failure, little is known about renal tubular function in this disease. We report on two patients with acute tubulo-interstitial nephritis who demonstrated abnormalities in proximal and distal tubular function. The first patient developed hyperkalemia presumably from a potassium secretory defect in the distal nephron. The second patient developed an incomplete Fanconi's syndrome with glycosuria and aminoaciduria and two heretofore unreported complications of acute interstitial nephritis: hypokalemia and hypomagnesemia secondary to urinary losses of these cations. Careful monitoring of renal tubular function is indicated in patients with acute tubulo-interstitial nephritis.