Sometimes a very large calculus nearly fills the calyceal system, with extensions into calyces that give the appearance of a stag's (deer) horns. Hence, the name "staghorn calculus". Seen here is a horn-like stone extending into a dilated calyx, with nearly unrecognizable overlying renal cortex from severe hydronephrosis and pyelonephritis. Nephrectomy may be performed because the kidney is non-functional and serves only as a source for infection.

Shown below are typical urinalysis findings for this condition, with evidence for "infection stones" of magnesium ammonium phosphate.



Macroscopic Urinalysis:

CharacteristicResult
ColorYellow
AppearanceCloudy
Leukocyte Esterase3+
NitritePos
pH7.5
ProteinTrace
Blood1+
Specific Gravity1.030
Ketones1+
GlucoseNeg
BilirubinNeg

Microscopic Urinalysis:

CharacteristicResult
WBC/hpf >100/hpf
RBC/hpf 5-10/hpf
Casts None
Other Many triple phosphate crystals