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
Urea
2NH3 + CO2
NH3 + H20
NH4+ + OH-
Magnesium ammonium phosphate crystals
– orthorhombic shape
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
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
Abdominal plain film showing b/l
radiopaque staghorn calculi
CT w/o contrast showing R staghorn
calculus
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
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
Surgical management
• Open surgery
• Percutaneous nephrolithotomy (PNL)
• Shock wave lithotripsy (SWL)
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