From the Guidelines
Yes, patients with renal tubular acidosis (RTA) are at increased risk for developing kidney stones, particularly those with distal RTA (Type 1), due to chronic metabolic acidosis, hypercalciuria, and alkaline urine pH. This condition leads to an increased concentration of crystal-forming substances in the urine, making stone formation more likely 1. The lifetime prevalence of nephrolithiasis is significant, with approximately 13% of men and 7% of women affected, and a 5-year recurrence rate of 35% to 50% without treatment 1.
Key factors contributing to stone formation in RTA patients include:
- Chronic metabolic acidosis, which leads to bone calcium release and hypercalciuria
- Alkaline urine pH, which promotes calcium phosphate crystal formation and aggregation
- Low citrate levels, which normally inhibit stone formation by binding to calcium
To prevent stone formation in RTA patients, treatment typically involves:
- Alkali therapy with potassium citrate (dose range 1-3 mEq/kg/day divided into 2-3 doses) or sodium bicarbonate to correct metabolic acidosis, reduce calcium excretion, and provide citrate
- Adequate hydration, with a recommendation to drink enough fluid to produce at least 2-2.5 liters of urine daily, as supported by the American College of Physicians' guideline recommending increased fluid intake to achieve at least 2 L of urine per day to prevent recurrent nephrolithiasis 1
- Thiazide diuretics may be added in cases of persistent hypercalciuria despite alkali therapy, as recommended by the American College of Physicians for patients with active disease in which increased fluid intake fails to reduce stone formation 1
From the FDA Drug Label
The effect of oral Potassium Citrate therapy in a non-randomized, non-placebo controlled clinical study of five men and four women with calcium oxalate/calcium phosphate nephrolithiasis and documented incomplete distal renal tubular acidosis was examined Potassium Citrate therapy was associated with inhibition of new stone formation in patients with distal tubular acidosis. The stone-passage remission rate was 67%. All patients had a reduced stone formation rate. Over the first 2 years of treatment, the on-treatment stone formation rate was reduced from 13±27 to 1±2 per year.
Patients with Renal Tubular Acidosis (RTA) may be at risk for developing kidney stones, specifically calcium oxalate or calcium phosphate stones. However, treatment with Potassium Citrate has been shown to reduce the formation of new stones in these patients. The stone-passage remission rate was 67% in one study, and all patients had a reduced stone formation rate 2.
From the Research
Relationship Between RTA and Kidney Stones
- Patients with Renal Tubular Acidosis (RTA) are at an increased risk of developing kidney stones, particularly calcium phosphate stones 3, 4, 5.
- The underlying mechanism involves the inability of the renal tubules to excrete acid normally, leading to an alkaline urinary pH and low citrate levels, which predispose to stone formation 3, 5.
- Distal RTA (dRTA) is a specific type of RTA that is commonly associated with kidney stone formation, and patients with dRTA often have a defect in excreting H+ ions, leading to an alkaline urinary pH and increased risk of stone formation 3, 4, 5.
Clinical Manifestations and Diagnosis
- Clinical manifestations of RTA can vary from mild symptoms, such as metabolic acidosis and hypokalemia, to more severe symptoms, such as failure to thrive, rickets, and nephrocalcinosis 3.
- Diagnosis of RTA can be challenging and requires a high index of suspicion, as well as measurement of urinary pH after an acid load, usually in the form of oral ammonium chloride 3, 5.
- Patients with incomplete dRTA may not have overt symptoms, but can still be at risk of developing kidney stones, and diagnosis may require provocative acid-loading challenges or genotyping of candidate genes 5.
Treatment and Management
- Treatment of RTA involves alkali therapy, preferably in the form of potassium citrate, to reverse the biochemical abnormalities and prevent stone formation 3, 4, 5, 6.
- Potassium citrate therapy has been shown to increase urinary pH and citrate levels, decrease urinary calcium, and inhibit new stone formation in patients with dRTA 4.
- Regular outpatient follow-up by a urologist and nephrologist is recommended for patients with RTA to monitor for kidney stone formation and adjust treatment as needed 3.