Bladder stone. Gross clinical specimen of a large bladder stone (urolith or vesical calculus). This is a mass of uric acid that calcifies due to obstruction of the bladder outlet or because the urine is highly concentrated. They often form as complications of other urinary problems, such as urinary tract infections or prostate gland enlargment. Bladder stones are far more frequent in men than in women. Treatment is either by chemical dissolution (alkalinization of the urine) or surgical therapy. The latter involves breaking up the stone by mechanical or ultrasonic means, or by using a laser. The fragments are then surgically removed through the urethra.