Medical Health Encyclopedia

Ultrasound detects gallstones as small as two millimeters in diameter with an accuracy of 90% to 95%. Some experts recommend that if an ultrasound does not detect stones, but gallstones are still strongly suspected, the test should be repeated.

Air in the gallbladder wall may indicate gangrene.

Ultrasound does not appear to be very useful for identifying cholecystitis in symptomatic patients who do not have gallstones. In one study, ultrasound detected some gallbladder abnormalities, no matter what the cause of the abdominal pain. In only a few cases, however, were the symptoms actually caused by cholecystitis.

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Ultrasound is also not as useful for common bile duct stones and cannot image the cystic duct. (Nevertheless, normal ultrasound results along with normal bilirubin and liver enzyme tests are very accurate indications that there are no stones in the common bile duct.)

An ultrasound variation called endoscopic ultrasound (EUS) is accurate and useful for patients with an intermediate risk for common bile ducts stones. Its accuracy is comparable to endoscopic retrograde cholangiopancreatography (ERCP), the standard for diagnosing stones in the common bile duct. However, if common duct stones are detected they cannot be removed. It is useful then when common bile duct stones are suspected but the patient is not clearly ill.

X-Rays. Standard x-rays of the abdomen may detect calcified gallstones and gas. Variations include oral cholecystography or cholangiography.

In oral cholecystography the patient takes a tablet containing a dye the night before the text. The dye fills the gallbladder and x-rays are used to take images of it the next day. It has been available since 1924 but has largely been replaced by ultrasound. It is more sensitive than standard x-rays, however, and may be useful in some cases for determining the structural and functional status of the gallbladder, often before nonsurgical procedures.