^BBladder stone.^b X-ray of a bladder stone (round, white, centre). Also called a ^Iurolith^i or a ^Ivesical^i ^Icalculus^i, this is usually a mass of uric acid that calcifies due to bladder obstruction or infection. Treatment ranges from chemical dissolution (alkalinization of the urine) to surgical therapy. The latter involves breaking up the stone by the use of mechanical, ultrasonic or laser techniques. The stone fragments may then be surgically removed through the urethra. The bones of the pelvis are also seen.