Staghorn calculus

• Large renal stones that are usually comprised of magnesium ammonium phosphate (struvite)
• Struvite stones are generally produced by urease-producing bacteria, primarily Proteus
• However, staghorn calculi can also be associated with Escherichia coli, Ureaplasma urealyticum, and occasionally Enterococcus, Klebsiella, Morganella, Mycoplasma, Corynebacterium, and staphylococci12