Bladder stone. Gross clinical specimen of a large bladder stone (urolith or vesical calculus). This is usually a mass of uric acid that calcifies due to obstruction of the bladder outlet. Treatment is either 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.