Ultrasonography is a diagnostic imaging method where sound waves are emitted from a small transducer (like a microphone) placed on the skin. The sound waves pass through the tissues and are invariably reflected and reabsorbed at interfaces between different tissues. The sound waves bounce back to the transducer in somewhat different form; the ultrasound machine computes the sound energy into a representative image. Typically, on an ultrasound image fluid appears black, and tissues such as fat appear bright or white

It is especially useful for patients complaining of right upper quadrant pain, for the evaluation of diseases of the gall bladder or biliary tract (tubes that drain the liver or gallbladder into the small intestine) and provides valuable information about a number of internal organs within the abdomen such as the liver. Among the many conditions that may be diagnosed confidently with ultrasound are gallstones, an inflamed gall bladder, dilatation of the bile ducts, abnormal liver texture, focal liver masses or the presence of free fluid within the abdomen which itself may be associated with a variety of gastrointestinal disorders