Hyperkalemic Distal Renal Tubular Acidosis Associated with Obstructive Uropathy

We studied renal function in 13 patients with obstructive uropathy and hyperkalemic metabolic acidosis to characterize the pathogenesis of this disorder. Base-line fractional potassium excretion was lower in all patients than in controls with similar glomerular filtration rates. Acetazolamide was given to 11 patients but failed to increase fractional potassium excretion to normal. In five patients, impaired potassium excretion was associated with decreased ammonium excretion, a urinary pH below 5.5 (5.18±0.07, mean ±S.E.M.), and aldosterone deficiency. In the remaining eight patients, the urinary pH did not fall below 5.5 (6.4±0.2) with acidosis, and we failed to lower the urinary pH and increase fractional potassium excretion to normal by administering a mineralocorticoid and sodium sulfate. A syndrome of hyperkalemic distal renal tubular acidosis may occur in patients with obstructive uropathy. In some patients, this syndrome results from a defect in hydrogen and potassium secretion in the distal nephron rather than from aldosterone deficiency. Obstructive uropathy should be included in the differential diagnosis of hyperkalemic acidosis and renal insufficiency. (N Engl J Med. 1981; 304:373–80.) URINARY acidification may be impaired before and after relief of unilateral or bilateral urinary-tract obstruction. 1 2 3 4 5 6 7 8 9 Studies in animals with experimentally induced obstructive uropathy have shown a transport defect in the distal nephron, characterized by impaired sodium reabsorption and decreased excretion of hydrogen and potassium. 8 , 9 In this report, we document the presence of a syndrome of hyperkalemic, hyperchloremic metabolic acidosis in patients with moderate chronic renal insufficiency associated with obstructive uropathy. In some of these patients, the diagnosis of obstructive uropathy was suspected solely because of hyperkalemic metabolic acidosis of uncertain origin. We studied renal function in these patients to investigate . . .