Can kidney stones cause recurrent Urinary Tract Infections (UTIs)?

Can Kidney Stones Cause Recurrent UTIs?

Yes, kidney stones can directly cause recurrent urinary tract infections, and this relationship works bidirectionally—stones can lead to infections, and certain infections can promote stone formation.

The Bidirectional Relationship

The association between kidney stones and recurrent UTIs is well-established and operates through two distinct mechanisms 1:

Stones Leading to Infections

• Bacterial harboring: Kidney stones of any composition can passively trap bacteria from coexistent UTIs, creating a protected niche where organisms persist despite antibiotic therapy 2, 3
• Biofilm formation: Bacteria residing within and on stone surfaces form biofilms that are resistant to both antibiotics and host immune responses 4
• Persistent infection source: Even metabolic stones (calcium oxalate, calcium phosphate) that are not primarily caused by infection can become secondarily infected and serve as a continuous source for recurrent UTIs 2, 5
• Clinical impact: Approximately 50% of patients with recurrent UTIs and asymptomatic renal calculi experience resolution of infections after complete stone removal, demonstrating the causal role stones play 6

Infections Leading to Stones (Struvite/Infection Stones)

• Urease-producing organisms: Specific bacteria (Proteus, Klebsiella, Pseudomonas, Staphylococcus—but notably NOT E. coli) produce urease enzyme that splits urea into ammonia and hydroxide 4, 7
• Alkaline environment: This creates an alkaline urinary pH that promotes crystallization of magnesium ammonium phosphate (struvite) and calcium carbonate apatite 1, 4
• Staghorn configuration: Struvite stones characteristically grow into large staghorn calculi that fill the renal pelvis and branch into calyces, which can destroy kidney function or cause life-threatening sepsis 4, 3
• Bacteria within stones: Unlike other stone types, bacteria reside within the stone matrix itself (not just on the surface), making the stones themselves infected 4

Critical Clinical Distinction: E. coli vs. Urease-Producing Bacteria

This is a common pitfall: E. coli causes approximately 75% of recurrent UTIs but does NOT typically produce urease and is NOT associated with struvite stone formation 7. However, E. coli can still become trapped in pre-existing metabolic stones and cause recurrent infections 7, 6.

• E. coli infections: More likely to resolve after stone removal (OR 0.34, p = 0.01) 6
• Enterococcus infections: More likely to persist after stone removal (OR 2.5, p = 0.04) 6
• Urease-producers (Proteus, Klebsiella): Directly cause struvite stone formation and require aggressive stone removal 4, 2

Management Algorithm

When to Intervene Surgically

Complete stone removal is essential in the following scenarios 1, 4:

• Struvite/infection stones: Mandatory complete removal to eradicate causative organisms, relieve obstruction, prevent further growth, and preserve kidney function 4, 3
• Recurrent UTIs with any stone type: Patients should be counseled for proactive stone removal when UTIs are recurrent, regardless of stone composition 8
• Residual fragments: Even small fragments may grow and serve as a source for recurrent UTI, particularly with suspected infection stones 1, 4
• High-risk patients: Those with diabetes, hypertension, immunocompromise, or anatomical abnormalities have higher risk of persistent infection and should be considered for stone removal 5, 6

Post-Removal Considerations

• Stone culture: Obtain stone culture (not just urine culture) for targeted antibiotic therapy tailored to bacterial prevalence 8
• Realistic expectations: Only 48-50% of patients with recurrent UTIs become infection-free after stone removal 6
• Risk factors for persistent infection: Black ethnicity (OR 13.7), hypertension (OR 2.8), and type 2 diabetes (OR 1.73) predict higher likelihood of continued infections despite stone removal 6
• Urease inhibitors: Acetohydroxamic acid (AHA) may benefit patients with struvite stones who cannot achieve complete stone removal, though extensive side effects limit use 1

Prevention Strategies

• Complete stone clearance: Patients treated for struvite stones remain at risk for recurrent UTI after stone removal if any fragments persist 1
• Urine culture monitoring: Obtain urine culture in patients with urinalysis suggestive of infection or history of recurrent UTIs 1
• Repeated imaging: Consider imaging in patients with repeated urease-producing bacterial infections to rule out calculus formation 7
• Address structural abnormalities: E. coli UTIs that recur rapidly (within 2 weeks) may indicate underlying structural abnormalities predisposing to stone formation 7