BSIP DR PICHARD T. / SCIENCE PHOTO LIBRARY BSIP DR PICHARD T. / SCIENCE PHOTO LIBRARY
Gall stone. Coloured ultrasound scan of a human abdomen showing the presence of a gall stone in the gall bladder. The position of the gall stone (green) is shown by an arrow. The gall bladder is the dark oval shaped area at upper centre. Gall stones are typically made up of cholesterol, along with bile pigments and calcium compounds. They occur when the chemical composition of the bile becomes unbalanced. Symptoms are rare unless the gall stone becomes stuck in the duct leading out of the gall bladder causing intense pain and nausea. Ultrasound scanning uses a transducer to emit high frequency sound waves, some of which are reflected back, producing the scan.
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