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Staghorn calculi – causes and treatment

Staghorn calculi – causes and treatment. Brad Weaver 8/19/08. 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

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Staghorn calculi – causes and treatment

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  1. Staghorn calculi – causes and treatment Brad Weaver 8/19/08

  2. 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-

  3. Magnesium ammonium phosphate crystals – orthorhombic shape

  4. Struvite stones cont. • Occur 3:1 ratio female:male • 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

  5. 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

  6. Abdominal plain film showing b/lradiopaquestaghorn calculi

  7. CT w/o contrast showing R staghorn calculus

  8. 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

  9. 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

  10. Surgical management • Open surgery • Percutaneous nephrolithotomy (PNL) • Shock wave lithotripsy (SWL)

  11. 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 May;153(5):1403-7

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