Long-Term Acidification of Urine in Patients Treated for Infected Renal Stones

Abstract

The effects of ammonium chloride, methenamine hippurate and ascorbic acid on urinary pH was studied in 14 normal subjects. A statistically significant reduction of urinary pH was recorded with ammonium chloride in daily doses of 1.5 and 3 g, but not with 2g of methenamine hippurate or 1.8 g of ascorbic acid. Long-term treatment with ammonium chloride in doses between 1.5 and 3 g was given to 11 patients in order to reduce the risk of new stone formation or growth of fragments remaining after disintegration of infected renal stones. Biochemical stone analyses showed struvite in 9 of the treated stones, and urine cultures verified the presence of urease-producing bacteria in 10 patients. Apart from ammonium chloride, the patients were treated with antibiotics, in 4 patients continuously and in the others during periods from 2 to 34 months. The patients were followed for an average period of 32 months. No adverse reactions were recorded with the dosage used. Initially, 6 patients were stone-free, whereas 5 had residual stone fragments with a largest diameter ranging from 4 to 20 mm. At follow-up, 2 patients were still stone-free, and of 5 patients with residual fragments 1 showed stable disease and 3 an improved stone situation. In 5 patients, 3 of whom had residual stone fragments, antibiotic treatment had been interrupted without infectious relapse. Our conclusion is that long-term urinary acidification is possible despite residual fragments and that it might be a beneficial therapeutic supplement to patients who have been treated for infected renal stones, particularly if disintegrated stone material resides in the kidney following extracorporeal or percutaneous lithotripsy procedures.

Diagnosis, Prevention, and Treatment of Catheter-Associated Urinary Tract Infection in Adults: 2009 International Clinical Practice Guidelines from the Infectious Diseases Society of America

“…Maintaining urinary pH below 6 or even below 5.5 is thought to be necessary to achieve bactericidal concentrations of formaldehyde [240]. Studies of ascorbic acid in dosages of up to 4 g per day have shown no significant effect on mean urinary pH [243][244][245], and dosages as high as 12 g per day or more frequent administration (eg, every 4 h) may be required to adequately acidify the urine [238]. Ammonium chloride might be more effective in acidifying the urine, but the potential for metabolic acidosis is a concern [244].…”

Metabolic Evaluation and Recurrence Prevention for Urinary Stone Patients: EAU Guidelines

“…Struvite precipitates only at pH >7.2 [83][84][85]. Proteus mirabilis accounts for more than half of all urease-positive infections [86,87] E U R O P E A N U R O L O G Y X X X ( 2 0 1 4 ) X X X -X X X measures include complete surgical stone removal [11], short-or long-term antibiotic treatment [88], urinary acidification using methionine [49] or ammonium chloride [50], and urease inhibition [51,52]. For severe infections, acetohydroxamic acid (Lithostat) may be an option (Table 12).…”

The Endourological Treatment of Renal Matrix Stones

“…Unfortunately, however, the length of the treatment period has never been clearly established. Several preparations for lowering urine pH might also be useful in treating patients with infected renal stones [19,20]. …”