Urinary calculi and infection

Abstract

Infection urinary stones resulting from urease-producing bacteria are composed by struvite and/or carbonate apatite. Bacterial urease splits urea and promotes the formation of ammonia and carbon dioxide leading to urine alkalinization and formation of phosphate salts. Proteus species are urease-producers, whereas a limited number of strains of other Gram negative and positive species may produce urease. Ureaplasma urealyticum and Corynebacterium urealyticum are urease-producers that are not isolated by conventional urine cultures, but require specific tests for identification. Primary treatment requires surgical removal of stones as complete as possible. Extracorporeal and endoscopic treatments are usually preferred, while open surgery is actually limited to few selected cases. Residual stones or fragments should be treated by chemolysis via ureteral catheter or nephrostomy or administration of citrate salts in order to achieve a stone-free renal unit. Postoperatively, recurrent urinary tract infection should be treated with appropriate antibiotic treatment although long-term antibiotic prophylaxis can cause resistance. Urinary acidification has been proposed for the prophylaxis of infection stones, but long-term acidification is difficult to achieve in urine infected by urease-producing bacteria. Urease inhibitors lead to prevention and/or dissolution of stones and encrustations in patients with infection by urea-splitting bacteria, but their use is limited by their toxicity. The administration of citrate salts involves an increase of the value of nucleation pH (pHn), that is the pH value at which calcium and magnesium phosphate crystallization occurs, in a greater way than the corresponding increase in the urinary pH due to its alkalinizing effect and resulting in a reduction of the risk of struvite crystallization. In conclusion prevention of the recurrence of infection stones can be achieved by an integrated approach tailored on the single patient. Complete clearance of the stone must be achieved by primary surgical procedure and residual fragments should be extensively treated. In the case of persistent infection, conservative measures, such as acidification and urease inhibitors or citrate administration, should be adopted to minimize its effect on urinary saturation with respect to struvite.

Nutritional Management of Kidney Stones (Nephrolithiasis)

“…They are typically very large and may be so large as to fill the renal pelvis (forming a "Staghorn calculus"). Their growth is rapid and they often grow back after surgical removal because infected fragments of stone have been left behind [ 38 39 40 ].…”

Urinary tract infection inducing stones: some clinical and chemical data

“…The literature indicates clearly that the pathogenesis of IKS is the consequence of a high urine pH and of the production of NH + 4 ions as a result of urea hydrolysis by bacterial urease [5,9,43,44]. As noted by Konieczna et al [45], urease (urea amidohydrolase) was the first enzyme to be crystallized (1926).…”

Medical Management of Urinary Calculi: Up to Date 2016

“…the concurrent increases in both carbon dioxide and ammonia cause a steep rise in urine pH to above 7.5. In this condition, ammonium magnesium phosphate and carbonate apatite reach supersaturation and form typical large staghorn calculi (70). The most common urease-producing bacteria are species of Proteus, Klebsiella, Providencia and Morganella, Staphylococcus aureus as well as Ureaplasma urealyticum and Corynebacterium urealyticum .…”