Oral Cholecystogram

The oral cholecystogram, or OCG, is a radiologic procedure for diagnosinggallstones. An oral cholecystogram is in contrast to anintravenous cholangiogram(IVC). The oral cholecystogram is rarely used, asultrasoundor CT are more accurate, faster techniques for identifyinggallstoneswithout exposure toiodine.

胆管本身不能seen on the x-ray in an OCG because the iodine is not concentrated in the ducts. Therefore, any gallstones lodged in the ducts will go undetected on OCG.

无法想象胆囊OCG可能occur for one of two reasons. First, a gallstone may have obstructed the cystic duct and prevented the iodine-containing bile from entering the gallbladder. Second, inflammation of the gallbladder -- usually due to gallstones -- may have interfered with the gallbladder's ability to concentrate bile and iodine. Whichever the cause, failure to visualize the gallbladder on an OCG strongly suggests a diseased gallbladder.

The risks of an oral cholecystogram are few. One, of course, is theradiation. However, in an OCG there is a relatively small amount of radiation from the x-rays.

Another risk involves the iodine. Some people areallergicto iodine. Fortunately, most people who are allergic know that they are, and therefore do not undergo the test.

The OCG finds gallstones 95% of the time. However, the OCG has tended to be replaced byultrasonographybecause ultrasonography is slightly better at diagnosing gallstones and can be done immediately without waiting one or two days for the OCG's iodine to be absorbed, excreted, and concentrated. The OCG also cannot give information about the presence of non-gallstone related diseases, which ultrasonography is sometimes able to do. A limitation of the OCG is that it does not work well when there is more than a minimal amount ofjaundice. Fortunately, most people with gallstones are not jaundiced.

As would be expected, ultrasonography sometimes finds gallstones that are missed by the OCG. Less frequently, the OCG finds gallstones that are missed by ultrasonography. For this reason, if gallstones are strongly suspected but ultrasonography does not show them, it is reasonable to consider doing an OCG. So OCGs are still done, and for good reason.