Renal

Struvite Nephrolithiasis

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Struvite Nephrolithiasis, Struvite Stone, Struvite Kidney Stone, Infection Stone, Triple-Phosphate Stone, Struvite Calculus, Magnesium Ammonium Phosphate Urolithiasis, Staghorn Calculus

  • See Also
  1. Nephrolithiasis
  • Epidemiology
  1. More common in women
  2. Represents 15-20% of Kidney Stones
  • Pathophysiology
  1. Most common cause of staghorn calculi
    1. Cysteine Nephrolithiasis also forms staghorn stones
  2. Components
    1. Magnesium
    2. Ammonium
    3. Calcium Phosphate
  • Risk Factors
  1. Neurogenic Bladder
  2. Urinary tract foreign body
  3. Urinary Tract Infection with urea-splitting Bacteria
    1. Infection alkalinizes urine (Urine pH>7)
    2. Increases ammonium concentration
    3. Bacterial causes
      1. Proteus Mirabilis
      2. Ureaplasma Urealyticum
      3. Klebsiella Pneumoniae
      4. Pseudomonas
  • Imaging
  1. Struvite Stones are faintly radiopaque
  2. Pneumaturia (gas in urinary tract) may be seen with Proteus
  • Complications
  1. Urinary Tract Infection (common)
    1. Intrarenal, non-obstructing staghorn stones are associated with Recurrent Urinary Tract Infections
    2. Non-obstructing renal staghorn stones are not a higher risk for Sepsis (until they obstruct)
  • Management
  1. Start Antibiotics immediately in obstructing staghorn stone suspected of infection
    1. Infected obstructive stones in general are high risk for bacteremia and overwhelming Sepsis
  2. Urgent urology Consultation
    1. Surgery delayed until afebrile for 48 hours
  3. Consider acetohydroxamic acid (Lithostat)
    1. Irreversible urease inhibitor
      1. Prevents struvite crystallization
    2. Risk of Deep Vein Thrombosis
    3. Indications
      1. Calculus-related severe infections
      2. Patients who are not surgical candidates
  • References
  1. Mobley (Feb 1999) Hospital Medicine, p. 21-38
  2. Goldfarb (1999) Am Fam Physician 60(8): 2269-76 [PubMed]
  3. Houshiar (1996) Postgrad Med 100(4): 131-8 [PubMed]
  4. Frassetto (2011) Am Fam Physician 84(11): 1234-42 [PubMed]
  5. Pietrow (2006) Am fam Physician 74(1): 86-94 [PubMed]
  6. Preminger (2007) J Urol 178(6): 2418-34 [PubMed]
  7. Portis (2001) Am Fam Physician 63(7):1329-38 [PubMed]
  8. Segura (1997) J Urol 158:1915-21 [PubMed]
  9. Teichman (2004) N Engl J Med 350:684-93 [PubMed]
  10. Trivedi (1996) Postgrad Med, 100(6): 63-78 [PubMed]