How are gallstones diagnosed?
Gallstones are diagnosed in one of two situations.
- When there are symptoms or signs that suggest the presence of gallstones and the diagnosis of gallstones is being pursued.
- Coincidentally while a non-gallstone-related medical problem is being evaluated.
Ultrasonography is the most important means of diagnosing gallstones. Standard computerized tomography (CT or CAT scan) and magnetic resonance imaging (MRI) may occasionally demonstrate gallstones; however, they are not as useful compared to ultrasonography.
Ultrasonography is a radiological technique that uses high-frequency sound waves to produce images of the organs and structures of the body. The sound waves are emitted from a device called a transducer and are sent through the body's tissues. The sound waves are reflected by the surfaces and interiors of internal organs and structures as "echoes." These echoes return to the transducer and are transmitted onto a viewing monitor. On the monitor, the outline of organs and structures can be determined as well as their consistency, for example, liquid or solid.
There are two types of ultrasonographic techniques that can be used for diagnosing gallstones: transabdominal ultrasonography and endoscopic ultrasonography.
For transabdominal ultrasonography, the transducer is placed directly on the skin of the abdomen. The sound waves travel through the skin and then into the abdominal organs. Transabdominal ultrasonography is painless, inexpensive, and without risk to the patient. In addition to identifying 97% of gallstones in the gallbladder, abdominal ultrasonography can identify many other abnormalities related to gallstones. It can identify:
- the thickened wall of the gallbladder when there is cholecystitis,
- enlarged gallbladder and bile duct due to obstruction by gallstones,
- pancreatitis, and
Transabdominal ultrasonography also may identify diseases not related to gallstones that may be the cause of the patient's problem, for example, appendicitis. The limitations of transabdominal ultrasonography are that it can only identify gallstones larger than 4-5 millimeters in size, and it is poor at identifying gallstones in the bile ducts.