Struvite: An Infection-Related Kidney Stone
Struvite is a type of kidney stone (calculus) composed of magnesium ammonium phosphate that forms in the presence of urinary tract infections with urease-producing bacteria. 1, 2
Composition and Formation
- Struvite stones are also known as "infection stones" because they form specifically in the presence of urinary tract infections
- Chemical composition: Magnesium ammonium phosphate (MgNH₄PO₄·6H₂O)
- Formation requires:
- Urease-producing bacteria (most commonly Proteus species)
- Alkaline urine pH
- Presence of magnesium, ammonium, and phosphate ions
Epidemiology and Risk Factors
- Account for approximately 15% of all urinary calculi 3
- More common in:
- Women
- Elderly individuals
- Patients with recurrent urinary tract infections
- Individuals with urinary tract abnormalities or obstruction
- Patients with neurogenic bladder
- Often present as large "staghorn" calculi that fill the renal collecting system
Clinical Presentation
- Flank pain
- Recurrent urinary tract infections
- Hematuria (blood in urine)
- Fever and chills if infection is severe
- May be asymptomatic until stones become large
Diagnosis
- Urine culture to identify causative organisms
- Note: Only about 30% of cases have urease-producing bacteria at the time of diagnosis 3
- Common organisms: Proteus species, E. coli, and Enterococcus
- Imaging studies:
- CT scan (most sensitive)
- Kidney-ureter-bladder (KUB) X-ray
- Ultrasound
- Stone analysis after removal confirms composition
- Most struvite stones (86.8%) are heterogeneous, containing other components such as calcium phosphate, calcium oxalate, or calcium carbonate 3
Treatment Approaches
Surgical Management:
- Percutaneous nephrolithotomy (PCNL) - primary approach for larger stones
- Shock wave lithotripsy (SWL) - for smaller stones
- Combination approaches for staghorn calculi
Medical Management:
- Appropriate antibiotic therapy based on culture results
- Urease inhibitors (e.g., acetohydroxamic acid) to prevent recurrence
- Acidification of urine
- Increased fluid intake
Prevention of Recurrence:
- Long-term antibiotic prophylaxis in selected cases
- Regular follow-up imaging
- Treatment of underlying urological abnormalities
- Dietary modifications (magnesium and phosphorus restriction may help)
Prognosis
- High recurrence rate without appropriate treatment
- Complete stone removal is essential to prevent regrowth
- Long-term monitoring is necessary due to risk of recurrent infections and stone formation
Recent Research
Recent studies have explored natural compounds that may inhibit struvite formation, including herbal extracts from curcumin, Boerhaavia diffusa Linn, and Rotula aquatica, which have shown promise in laboratory studies 4.