Medical Health Encyclopedia

If the doctor only suspects common duct stones, however, identifying them is problematic. It requires blood tests, imaging tests, invasive procedures, or some combination that serve both for detection and possibly removal.

Laboratory Tests. Evidence that may suggest common bile duct stones includes dark urine, jaundice, or pancreatitis. In such cases, the doctor may perform certain blood tests. Elevated levels of the following suggest the presence of common duct stones:

• Alkaline phosphatase (ALP). Elevated levels of this enzyme are typically the first signs of common bile duct stones.
• Bilirubin (the orange-yellow pigment found in bile). Bilirubin levels increase after alkaline phosphatase rises.
• Liver enzymes known as aspartate aminotransferase (AST) and alanine aminotransferase (ALT). These enzymes may temporarily spike if the stone passes into the small intestine.

A number of techniques, particularly endoscopic retrograde cholangiopancreatography (ERCP), endoscopic ultrasound (EUS) and magnetic resonance cholangiography (MRC), are proving to be equally effective for detecting common bile duct stones. Only ERCP, however, allows removal of the stones, but it is invasive. A National Institutes of Health expert panel has endorsed the use of ERCP as a diagnostic technique for patients who are clearly ill with symptoms of gallstones. For patients who are not as sick, the panel recommended noninvasive imaging techniques.

Imaging Techniques

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Ultrasound. Ultrasound is a simple, rapid, and noninvasive imaging technique. It is the diagnostic method most frequently used to detect gallstones and is the method of choice for detecting acute cholecystitis. The patient must not eat for six or more hours before the test, which takes only about 15 minutes. During the procedure, the doctor can check the liver, bile ducts, and pancreas and quickly scan the gallbladder wall for thickening (characteristic of cholecystitis).