From the Guidelines
Non-obstructive kidney stones can indeed be a source of infection, particularly those composed of struvite or calcium carbonate apatite, which are strongly associated with urinary tract infections caused by urease-producing organisms. These stones can harbor bacteria within their matrix, creating a protected environment where microorganisms can multiply and potentially cause recurrent urinary tract infections 1. The bacteria most commonly involved include Proteus, Klebsiella, Pseudomonas, and E. coli, which can produce urease enzymes that contribute to stone formation and growth. Patients with non-obstructive stones may experience symptoms such as persistent or recurrent urinary tract infections despite appropriate antibiotic therapy.
Key Considerations
- The formation of struvite stones is often a consequence of urinary infection with a urease-producing organism, and patients treated for these stones may still be at risk for recurrent UTI after stone removal 1.
- Management typically involves culture-specific antibiotics for acute infections, with common regimens including fluoroquinolones (e.g., ciprofloxacin 500mg twice daily for 7-14 days) or trimethoprim-sulfamethoxazole (160/800mg twice daily for 7-14 days).
- For stones composed of struvite or calcium carbonate apatite that are associated with infection, complete surgical removal may be necessary to eliminate the bacterial reservoir.
- Long-term prevention strategies include adequate hydration, urine acidification with cranberry products or vitamin C supplements, and in some cases, low-dose prophylactic antibiotics such as nitrofurantoin 50-100mg daily.
- Regular follow-up with urinalysis and imaging is important to monitor for stone growth or new infection development.
Treatment Approach
- Complete stone removal should remain a therapeutic goal, especially when a struvite/calcium carbonate/apatite stone is present, as it can help eradicate causative organisms, relieve obstruction, prevent further stone growth, and preserve kidney function 1.
- The choice of treatment should be individualized based on the patient's specific condition, including the type of stone, presence of infection, and overall health status.
From the Research
Non-Obstructive Kidney Stones as a Source of Infection
- Non-obstructive kidney stones can be a source of infection, as they can harbor bacteria and contribute to the development of urinary tract infections (UTIs) 2, 3, 4.
- The formation of infection stones is often associated with urease-positive urinary tract infections, which can lead to the development of struvite and carbonate apatite stones 3, 4.
- Studies have shown that the removal of non-obstructive kidney stones can help reduce the incidence of recurrent UTIs in some patients 5.
- However, the decision to remove small, non-obstructing renal stones in adults with recurrent UTIs requires careful consideration of multiple factors, including the patient's medical history, imaging studies, and laboratory results 6.
Predictors of Recurrent Infections
- Certain factors, such as type 2 diabetes mellitus, hypertension, and black ethnicity, have been associated with a higher risk of recurrent infections after stone removal 5.
- The type of infecting organism can also influence the likelihood of recurrent infections, with Escherichia coli infections being more likely to resolve and Enterococcus infections being more likely to persist 5.
Management of Non-Obstructive Kidney Stones
- The management of small, non-obstructing renal stones in adults with recurrent UTIs remains unclear and requires a comprehensive evaluation of the patient's condition 6.
- Patients with non-obstructive kidney stones and recurrent UTIs should be evaluated for additional possible etiologies and managed accordingly before considering stone removal 6.
- Antibiotic prophylaxis and therapy may be necessary to prevent and treat infections associated with kidney stones, especially in patients with infection stones or those who are immunocompromised 2.