Table 1.

Stone composition (table modified from Moe¹³).

Stone composition	Frequency	Comment
Calcium	80%	Radio-opaque
Struvite stones	5–15%	Associated with infection
Uric acid	5–10%	Radiolucent
Cystine	1–2.5%
Ammonium urate	0.5–1%
Others: xanthine, protein matrix 2,8-dihydroxyadenine drugs, e.g. indinavir, triamterene	Rare