Renal tubular defects in recurring bilateral nephrolithiasis

A metabolic study was performed in 28 patients with bilateral recurrent calcium-containing renal staghorn calculi and chronic pyelonephritis ("obstructive nephropathy"). Fourteen had normal GFR and 14 mild renal insufficiency. Ten normal subjects were used as controls. Under basal conditions, polyuria and negative sodium balance were commonly observed in patients with obstructive nephropathy and normal renal function. After an acute acid load (NH4Cl) an acidifying defect, i.e. high values for urine pH and reduced excretion of titratable acid and ammonium, was observed in 64% of patients with normal GFR and in 71.4% of those with renal insufficiency. During intravenous infusion with neutral sodium phosphate, the urine pH changed little but the rate of excretion of titratable acid increased in direct proportion to that of urinary phosphate in both groups of patients. These results, associated with the finding of normal blood pH in almost all patients, lead to the conclusion that an incomplete Type 1 or "distal" renal tubular acidosis is a frequent complication of obstructive nephropathy secondary to bilateral nephrolithiasis. The anatomical abnormalities of renal tubules and collecting ducts and the superimposed interstitial nephritis might be the pathogenetic factors responsible for the acidifying defect and for the impairment in sodium and water conservation.