Staghorn calculi – causes and treatment

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Staghorn calculi causes and treatment

• Brad Weaver
• 8/19/08

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Struvite stones

• Composed of magnesium ammonium phosphate triple
  phosphate crystals
• Precipitate at alkaline pH created by urease
  producing bacteria such as Proteus or Klebsiella
  
• Urease
• Urea 2NH3 CO2
• NH3 H20 NH4 OH-

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Magnesium ammonium phosphate crystals
orthorhombic shape
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Struvite stones cont.

• Occur 31 ratio femalemale
• More common in those anatomically predisposed to
  infection such as with neurogenic bladder or
  urinary diversion
• Staghorn calculi may also contain mixed
  calcium/struvite or all calcium stones
• The presence of calcium warrants metabolic workup
  for cause of stones

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Struvite stone symptoms

• Often no symptoms directly related to stone
• May present with UTI, flank pain, hematuria
• Passage of struvite stone is rare
• Can rapidly grow and lead to chronic
  pyelonephritis and parenchymal scarring
• Struvite stones are radiopaque and can be seen on
  AXR and CT

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Abdominal plain film showing b/l radiopaque
staghorn calculi
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CT w/o contrast showing R staghorn calculus
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Cystine stones

• Cystine stones may also form staghorn calculi
• Cystinuria is a rare autosomal recessive disease
  responsible to 1-2 of stone formers
• Caused by mutations in genes, SLC3A1 and SLC7A9,
  that are involved in amino acid transport
• Median age of onset of kidney stones is 12

• Hexagonal crystals in urine sediment
• Treatment with fluids, alkali, cystine binding
  drugs penicillamine, tiopronin, and captopril

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Medical management of staghorn calculi

• Dietary phosphorus reduction
• Antibiotics rarely successful at eradicating
  bacteria in struvite stone
• Acetohydoxamic acid (AHA, Lithostat) is a urease
  inhibitor that has been shown to stop stone
  growth in 80 vs. 40 on placebo. Use is limited
  by frequent side effects including palpitations,
  nausea, and hemolytic anemia

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Surgical management

• Open surgery
• Percutaneous nephrolithotomy (PNL)
• Shock wave lithotripsy (SWL)

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Retrospective study

• 112 patients with staghorn calculus with mean
  follow up 7.7 years
• Renal deterioration occurred in 28
• Worse outcome associated with solitary kidney,
  recurrent stones, hypertension, urinary
  diversion, and neurogenic bladder

J Urol 1995 May153(5)1403-7