lithiasis /lithī″əsis/ [Gk, lithos, stone, osis, condition] , the formation of calculi in the hollow organs or ducts of the body. Calculi are formed of mineral salts and may irritate, inflame, or obstruct the organ in which they form or lodge. Lithiasis occurs most commonly in the gallbladder, kidney, and lower urinary tract. Lithiasis may be asymptomatic, but more often the condition is extremely painful. Surgery may be necessary if the stones cannot be excreted spontaneously. Lower urinary tract calculi often can be dissolved. See also biliary calculus, cholelithiasis, renal calculus, urinary calculus.
