Renal tubular acidosis

Urologic manifestations of nonurologic disease urolithiasis

Patients with nephrolithiasis may have coexistent diseases that play a causative role in stone formation. A stone event may be the initial manifestation of the disorder and the urologist may play a major diagnostic role. Regulation or correction of the disorder may eradicate or dramatically attenuate stone activity. In some patients, metabolic abnormalities persist, however, and the therapeutic strategies that were reviewed in this manuscript may need to be implemented. Stone disease may also be induced by drugs that are used to treat a number of disease processes. When this occurs, the drug will usually need to be discontinued and alternative therapy should be instituted.

Pathophysiology of incomplete renal tubular acidosis in recurrent renal stone formers: evidence of disturbed calcium, bone and citrate metabolism

Urinary acidification, bone metabolism and urinary excretion of calcium and citrate were evaluated in 10 recurrent stone formers with incomplete renal tubular acidosis (iRTA), 10 recurrent stone formers with normal urinary acidification (NUA) and 10 normal controls (NC). Patients with iRTA had lower plasma standard bicarbonate after fasting (P < 0.01) and lower urinary excretion of titratable acid (P < 0.05) and citrate (P < 0.01) compared with NUA patients and NC, and higher urinary excretion of ammonia (P < 0.05) compared with NC (P < 0.05). Hypercalciuria was found in 6 of 10 patients with iRTA compared with 3 of 10 with NUA, and 0 of 10 NC. The citrate/calcium ratio in urine was significantly reduced in iRTA compared with the value in NUA (P < 0.01), and in NUA compared with NC (P < 0.05). Biochemical markers of bone formation (serum osteocalcin) and bone resorption (urinary hydroxyproline) were significantly increased in iRTA compared with NUA and NC (P < 0.01), indicating increased bone turnover in stone formers with iRTA. Stone formers with iRTA thus presented with disturbed calcium, bone and citrate metabolism--the same metabolic abnormalities which characterize classic type 1 RTA. Mild non-carbonic acidosis during fasting may be a pathophysilogical factor of both nephrolithiasis and disturbed bone metabolism in stone formers with iRTA.

Renal acidification defects in medullary sponge kidney

Thirteen patients with medullary sponge kidney underwent a short ammonium chloride loading test to investigate their renal acidification capacity. All but 1 presented with a history of recurrent renal calculi and showed bilateral widespread renal medullary calcification on X-ray examination. Nine patients had some form of renal acidification defect; 8 had the distal type of renal tubular acidosis, 2 the complete and 6 the incomplete form. One patient had proximal renal tubular acidosis. These findings, which suggest that renal acidification defects play an important role in the pathogenesis of renal calculi in medullary sponge kidney, have considerable therapeutic implications.

Urine composition and stone formation during treatment with acetazolamide

Twelve patients who formed renal stones during acetazolamide treatment for glaucoma were studied. Calcium phosphate was the dominating component in the stones. Long term treatment with acetazolamide decreased urinary citrate markedly, which will result in an increased ion-activity product of calcium phosphate and a decreased inhibiting property of urine on calcium phosphate crystallization. The treatment also increased urinary oxalate which together with a low citrate might increase the risk of calcium oxalate crystallization. However, an estimate of the ion-activity product of calcium oxalate in urine (AP [CaOx]-index) was unaffected by the treatment and calcium oxalate was a minor component of the stones.

Canine distal renal tubular acidosis and urolithiasis

Distal RTA is characterized by decreased distal renal tubular hydrogen ion secretion, decreased ability to acidify urine, hypercalciuria, hyperphosphaturia, hypocitraturia, and metabolic acidosis. Because of the resulting alterations in urine composition and pH, patients with distal RTA are predisposed to urolithiasis and renal calcification. Diagnosis of distal RTA is important because it is a potentially reversible disorder that, left untreated, may cause nephrocalcinosis, recurrent urolith formation, moderate to severe metabolic acidosis, and renal failure.