"Staghorn calculi, also sometimes called coral calculi, are renal calculi that obtain their characteristic shape by forming a cast of the renal pelvis and calyces, thus resembling the horns of a stag. They refer to struvite calculi involving the renal pelvis and extending into at least two calyces7."
"Staghorn calculi are composed of struvite (chemically this is magnesium ammonium phosphate or MAP) and are usually seen in the setting of recurrent urinary tract infection with urease-producing bacteria (e.g. Proteus, Klebsiella, Pseudomonas and Enterobacter). Urease hydrolyses urea to ammonium with an increase in the urinary pH 3-5."
"There is usually little differential, provided intravenous contrast has not been administered. In the latter situation, the opaque collecting system may be attributed to contrast rather than the calculus, especially when staghorn calculi are bilateral."