How are gallstones diagnosed?
The most commonly used test to detect gallstones is an ultrasound. Ultrasound is a painless and accurate procedure that transmits high-frequency sound waves through body tissues. The echoes are recorded and transformed into video or photographic images of the internal structures of the body. While no test is 100%, this is a very accurate test for diagnosing gallstones. There are other radiology tests that are sometimes used, but ultrasound is the main tool for diagnosing gallbladder disease.
In general, ultrasound does not visualize the common bile duct well. Though stones in this duct aren’t as common, they can happen. If they are suspected, the following tests may be done:
Endoscopic retrograde cholangiopancreatography (ERCP): This is both a test and a possible treatment for common bile duct stones. When used as a test, an endoscope—a flexible tube with a light and a camera attached—is inserted into the patient's mouth, down the throat, and into the stomach and small intestine. A dye is injected to allow the bile ducts to stand out. If there are gallstones in the bile duct, they can be removed by the endoscope. This scope cannot remove stones contained within the gallbladder.
Illustration showing the flexible tube for the ERCP can diagnose and sometimes treat gallstones.
Magnetic resonance cholangiopancreatography (MRCP): In MRCP, the bile ducts are examined with magnetic resonance imaging (MRI), a test that uses a large magnet, radio waves, and a computer to produce very clear images of parts of the body. Unlike ERCP, MRCP can only diagnose common bile duct stones. It cannot remove them. However, MRCP’s advantage over ERCP is that it is the safer alternative, so often physicians will opt for MRCP initially.
Endoscopic ultrasound (EUS): This procedure combines endoscopy with ultrasound (there’s a probe at the tip of the scope). Like ERCP, this scope is passed through the mouth and advanced to the common bile duct and gallbladder region. It visualizes the common bile duct well. Similarly to MRCP, gallstones are identified but not removed during this procedure. If common bile duct stones are demonstrated by EUS (or MRCP), then an ERCP will generally follow to remove them.
Illustration showing how the scope of the can go into the body to view the gallstones.