Diagnosis of Gallstones
The best test to diagnose gallstones in the gallbladder is an abdominal ultrasound, which uses sound waves to create images of the inside of the gallbladder. It is a noninvasive, painless test that is performed by placing an ultrasound probe on the outside of your abdomen.
No special preparation is required aside from fasting for six to eight hours. Abdominal ultrasound can detect gallstones as small as 2 mm. If you have acute cholecystitis, ultrasound can detect thickening of the gallbladder wall as well as the presence of inflammatory fluid (pus that contains bacteria and inflammatory cells) in and around the gallbladder. Abdominal ultrasound can also detect widening of the common bile duct due to obstruction by a stone.
If your doctor suspects that there is a gallstone in your common bile duct, an endoscopic ultrasound may be performed. This test uses a special endoscope with an ultrasound probe at its tip.
Computed tomography (CT) produces cross-sectional images of the human body using high-resolution x-rays that are processed by a computer. It involves lying on a special table while x-rays are passed through your body. Like abdominal ultrasound, CT is painless and noninvasive. It is better than ultrasound at detecting complications of acute cholecystitis, such as perforation of the gallbladder or bile ducts and the formation of an abscess (a localized accumulation of pus).
A hepatobiliary scintigram, also called a hepato-iminodiacetic acid (HIDA) scan, is used to evaluate the passage of bile through the bile ducts and gallbladder and to detect obstruction of the cystic duct. This test involves the intravenous injection of a small amount of a radioactive substance into a vein in your arm. The radioactive substance is removed from the blood by the liver and then secreted into the bile ducts. A special camera detects the presence of the radioactivity and creates a computer image of the bile ducts.
The procedure is safe and exposes you to only small amounts of radioactivity.
Endoscopic retrograde cholangiopancreatography (ERCP) is the best way to diagnose stones in the bile ducts. It uses a special side-viewing endoscope to locate the opening to the duodenum and to place a thin catheter in the bile ducts. A contrast agent is then injected into the bile ducts and x-rays are taken, allowing your doctor to study the anatomy of the ducts and identify any defects or blockages caused by stones, strictures, or masses.
A noninvasive, painless alternative to ERCP is magnetic resonance cholangiopancreatography (MRCP). It uses radiofrequency waves to create pictures of the bile and pancreatic ducts. During the procedure, you will lie very still in the magnetic resonance imaging (MRI) scanner. The test takes about 20 minutes and may not require the injection of a contrast agent.