Not all urinary calculi require surgical treatment. Intervention generally is required only if there is pain, obstruction, or associated urinary tract infection. In certain situations, however, therapy may be indicated for asymptomatic calculi. For example, surgical removal of staghorn calculi is recommended in most individuals because of the risk to renal function posed by an untreated staghorn calculus. Also, the removal of smaller calculi, regardless of symptoms, often is considered for occupational, social, or health reasons. Airline pilots, or anybody for whom a sudden attack of renal colic might produce unacceptable or even dangerous interruptions of occupation or lifestyle, are candidates for the treatment of asymptomatic urolithiasis. Patients about to undergo organ transplantation or implantation of artificial prostheses should be rendered stone-free to minimize the risk of urinary tract infection, which could prove life-threatening in such patients.