A calculus is a solid concretion, or stone, that forms within the body from the precipitation of minerals and other substances from body fluids. The most common types encountered in sonography are gallstones, or biliary calculi, and kidney stones, or renal calculi. On ultrasound, calculi typically appear as strongly echogenic structures that produce a distinct posterior acoustic shadow. The detection of calculi is one of the most frequent indications for abdominal ultrasound, and the characteristic appearance of a bright stone with a trailing shadow is one of the most recognizable findings in all of diagnostic ultrasound.
Sonography Term