A bladder calculus, or bladder stone, is a hard mineral deposit that forms within the urinary bladder, usually as a result of incomplete bladder emptying, urinary tract infections, or stones that have passed from the kidneys. On ultrasound, bladder stones appear as hyperechoic, rounded structures within the bladder that produce a characteristic posterior acoustic shadow. Unlike gallstones, which remain fixed to the gallbladder wall, bladder stones typically move freely when the patient changes position, rolling to the most dependent part of the bladder. This mobility is a helpful diagnostic feature that distinguishes bladder stones from masses or polyps that are attached to the bladder wall.
Sonography Term