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Kidney stone

Also known as kidney calculus or renal calculus. Any of the hard concretions varying in size from a tiny particle to staghorn calculi which may fill the renal pelvis; 90% are calcium, the remaining 10% being composed mainly of cystine, uric acid, or struvite. Small calculi may be passed for years without symptoms, while larger ones may cause renal colic, hematuria, or ureteral or pelvic obstruction leading to hydronephrosis or infection.