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Definition This is an x-ray exam of the gallbladder (GB), a sac-like organ that stores bile that is located under the liver. The study involves taking tablets containing dye (contrast) which outline any abnormalities when x rays are taken the following day. The test was once the standard for diagnosing diseases of the GB such as gallstones, but is used less frequently now. This is due to advances in diagnostic ultrasound, which is quick, accurate and doesn't involve exposure to ionizing radiation. When functional parameters of the gallbladder need to be demonstrated, scintigraphy is now the study of choice. OCG, however, can be useful when a gallbladder is contracted down due to the presence of many, many gallstones. It can also help determine whether the cystic duct is clear, prior to surgical procedures such as lithotripsy. OCG may also be used to evaluate gallbladder disease that doesn't involve gallstones, such as adenomyomatosis of the gallbladder or cholesterolosis of the gallbladder. Purpose This test, also known as an oral cholecystogram or OCG, is usually ordered to help physicians diagnose disorders of the gallbladder, such as gallstones and tumors, which show up as solid dark structures. It is performed to help in the investigation of patients with upper abdominal pain. The test also measures gallbladder function, as the failure of the organ to visualize can signify a non-functioning or diseased gallbladder. The gallbladder may also not visualize if the bilirubin level is over 4 and the study should not be performed under these circumstances. Precautions Your physician must be notified if you are pregnant or allergic to iodine. Patients with a history of severe kidney damage, have an increased risk of injury or side effects from the procedure. In those cases, ultrasound is commonly used instead of the x-ray examination. Some people experience side effects from the contrast material (dye tablets), especially diarrhea. During preparation for the test, patients should not use any laxatives. Diabetics should discuss the need for any adjustment in medication with their physician. Description The exam is performed in the radiology department. The night before the test, patients swallow six tablets (one at a time) that contain the contrast (x-ray dye). The following day at the hospital, the radiologist examines the gallbladder with a fluoroscope (a special x ray that projects the image onto a video monitor). Sometimes, patients are then asked to drink a highfat formula that will cause the gallbladder to contract and release bile. X rays will then be taken at various intervals. There is no discomfort from the test. If the gallbladder is not seen, the patient may be asked to return the following day for x rays. Preparation The day before the test patients are instructed to eat a high fat lunch (eggs, butter, milk, salad oils, or fatty meats), and a fat-free meal (fruits, vegetables, bread, tea or coffee, and only lean meat) in the evening. Two hours after the evening meal, six tablets containing the contrast medium, are taken, one a time. After that, no food or fluid is permitted until after the test. Aftercare No special care is required after the study. Risks There is a small chance of an allergic reaction to the contrast material. In addition, there is low radiation exposure. X rays are monitored and regulated to provide the minimum amount of radiation exposure needed to produce the image. Most experts feel that the risk is low compared with the benefits. Pregnant women and children are more sensitive to the risks of x rays, and the risk versus benefits should be discussed with the treating physician. Normal results The x ray will show normal structures for the age of the patient. The gallbladder should visualize, and be free of any solid structures, such as stones, polyps, etc. Abnormal results Abnormal results may show gallstones, tumors, or cholesterol polyps (a tumor growing from the lining that is usually noncancerous). Typically stones will "float" or move around as the patient changes position, whereas tumors will stay in the same place. Key Terms - Bile
- A yellow-green liquid produced by the liver, which is released through the bile ducts into the small intestines to help digest fat.
- Bilirubin
- A reddish-yellow pigment formed from the destruction of red blood cells, and metabolized by the liver. Levels of bilirubin in the blood increase in patients with liver disease or blockage of the bile ducts.
- Ultrasound
- A non-invasive procedure based on changes in sound waves of a frequency that cannot be heard, but respond to changes in tissue composition. It requires no preparation and no radiation occurs; it has become the "gold standard" for diagnosis of stones in the gallbladder, but is less accurate in diagnosing stones in the bile ducts. Gallstones as small as 2 mm can be identified.
For Your Information Books - Levenson, Deborah E. and Fromm, Hans. "Oral Cholecystogram." In Hepatology: A Textbook of Liver Disease, edited by David Zakim and Thomas D. Boyer et al. Philadelphia: W.B. Saunders Company. 1996, p.1883.
- Sleisenger and Fordtran's Gastrointestinal and Liver Disease: Pathophysiology/Diagnosis/ Management, edited Mark Feldman, et al. Philadelphia: W.B. Saunders Company, 1998.
- Zeaman, Robert K. "Oral Cholecystography." In Bockus Gastroenterology, edited by William S. Haubrich et al. Philadelphia: W.B. Saunders Company. 1995, pp. 208-211.
Other- "Gall Bladder Exam." Harvard Medical School. http://www.bih.harvard.edu/radiology/Modalities/Xray/ xraysSubdivsf/gallbl.html.
- "Gallstones." National Institutes of Health.
- "Oral cholecystogram." Healthanswers.com.
Source: Gale Encyclopedia of Medicine, Published December, 2002 by the Gale Group
The Essay Author is Rosalyn Carson-DeWitt MD.
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