From the Guidelines
Struvite stones are primarily caused by urease-producing bacteria, with Proteus species, especially Proteus mirabilis, being the most common causative organism, as well as other bacteria such as Klebsiella pneumoniae, Pseudomonas aeruginosa, Staphylococcus aureus, Ureaplasma urealyticum, and certain strains of Escherichia coli 1. These bacteria produce the enzyme urease, which hydrolyzes urea into ammonia and carbon dioxide, creating an alkaline environment that promotes the crystallization of magnesium ammonium phosphate (struvite) and calcium phosphate, leading to stone formation. Key points to consider include:
- Struvite stones typically develop in the setting of chronic or recurrent urinary tract infections with these organisms 1.
- They are more common in women and can grow rapidly to form large "staghorn" calculi that fill the renal collecting system 1.
- Treatment requires both surgical removal of the stones and appropriate antibiotic therapy to eradicate the underlying infection, as these stones will recur if the infection persists 1.
- Patients with struvite stones should be monitored for reinfection 1. The most recent and highest quality study, published in 2014, emphasizes the importance of monitoring patients with struvite stones for reinfection 1, highlighting the need for ongoing management and prevention of recurrent urinary tract infections.
From the Research
Bacterial Organisms Causing Struvite Stones
The formation of struvite stones is often associated with urinary tract infections caused by specific bacterial organisms. These bacteria produce urease, an enzyme that plays a crucial role in the crystallization process of struvite stones.
- Urease-Producing Bacteria: The most common bacteria implicated in the formation of struvite stones are those that produce urease, such as Proteus species 2, 3, 4, 5.
- Proteus Species: Proteus mirabilis is a prominent example of a urease-producing bacterium that can lead to the formation of struvite stones 2, 4, 5, 6.
- Other Urease-Producing Bacteria: Other bacteria, including Klebsiella pneumoniae, Klebsiella oxytoca, and Pseudomonas aeruginosa, have also been found to produce crystals, including struvite, although their role in struvite stone formation may vary 2.
- Ureaplasma urealyticum and Corynebacterium urealyticum: These bacteria are also urease-producers but require specific tests for identification as they are not isolated by conventional urine cultures 3.
Mechanism of Struvite Stone Formation
The mechanism by which these bacterial organisms cause struvite stones involves the production of urease, which splits urea into ammonia and carbon dioxide, leading to urine alkalinization and the formation of phosphate salts 3, 4, 5, 6. This process creates an environment conducive to the crystallization of struvite and other minerals, resulting in the formation of infectious urinary stones.