struvite (magnesium ammonium phosphate) stone

Etiology

• all patients with struvite stones are infected with urease-producing bacteria:
• Proteus
• Staphylococcus
• Klebsiella
• Pseudomonas
• E coli

Epidemiology

• more common in women than men
• most frequent in elderly women with chronic urinary tract infections

Clinical manifestations

• struvite stones may be staghorn & bilateral (50%)

Laboratory

• pH of the urine is alkaline < 7.5, occasionally > 7.8
• stones contain bacteria
• struvite crystals in urine (image)

Management

• antibiotic treatment urinary tract infection caused by urease-producing bacteria helps prevent struvite stone
• once struvite stones are formed, surgery provides definitive treatment
  • presurgical antibiotics
  • percutaneous stone extraction (+/- extracorporeal shock-wave lithotripsy)
• bactericidal antibiotics for 6-12 months
• acetohydroxamic acid (urease inhibitor) rarely used due to toxicity

More general terms

• urinary calculus (stone, nephrolithiasis, urolithiasis)

More specific terms

• staghorn calculus

Additional terms

• struvite (magnesium ammonium phosphate, MgNH4PO4)
• urease