Gastrointestinal imaging

From IKE
Jump to: navigation, search

Esophageal diseases

Radionuclide esophageal motility studies are sometimes used to evaluate abnormal esophageal motility. This is a quantitative evaluation of the swallowing of radioactive solids and liquids.

Gastroesophageal reflux of stomach contents into the esophagus can be diagnosed by administration of a radioactive drink (acidified orange juice) followed by graded abdominal compression, which is accomplished by inflating a large pneumatic binder around the abdomen.

Stomach diseases

Nuclear imaging techniques can be used to help patients with recurrent gastric ulcers. Though patients may permanently respond to a short course of antacid therapy, there is recurrence of ulceration in some patients. Many of these patients have been found to have an infection in the stomach wall (helicobacter pylori), which can be diagnosed by administering radioactive urea orally. Helicobacter pylori have the unique ability to break down urea resulting in carbon dioxide release (radioactive carbon dioxide in ths case). The radioactive carbon dioxide can be detected in the breath with a urea breath test.

Some patients have poor emptying of the gastric contents, which can result in bloating after eating. This can be detected by administering a radiolabelled meal and quantitatively imaging the stomach after the meal, also known as a gastric emptying study. If there is poor clearance of the radioactivity in the stomach, obviously the stomach is not emptying quickly.

Some patients with anemia have large red blood cells (aka megaloblastic anemia), which can lead to neurological symptoms. Serum Vitamin B12 is usually ordered and is below normal, a condition known as pernicious anemia.


Small bowel and colon diseases

Upper gastrointestinal bleeds are usually diagnosed by endoscopy. GI bleeding when acute but not life-threatening can be diagnosed by radiolabelling the patient's red blood cells and taking pictures, a procedure that is more important for lower GI bleeding.

More invasive angiograms can be performed if extravasation of radiolabelled red blood cells into the gastrointestinal tract is observed. The GI bleed may even be treated during angiography by occluding the vessel supplying the bleed.

Patients with subacute or chronic diarrhea may have active inflammation such as Crohn's disease or ulcerative colitis. This can be diagnosed by labeling the patient's white blood cells and taking pictures of the abdomen, a procedure referred to as a white blood cell scan. Accumulation of white blood cells in the distal small bowel indicates active Crohn's disease, whereas accumulation of radiolabelled white blood cells in the colon indicates active ulcerative colitis. Patients with abdominal abscesses or abscesses anywhere will have focal accumulation of white blood cells at the abscess on a white blood cell scan.

The white blood cell scan is an important diagnostic test.

Gallbladder diseases

Patients can have acute right upper quadrant pain. If an ultrasound of the gall bladder shows stones in the gallbladder (gallstones), there is a high probability that the right upper quadrant pain is due to acute cholecystitis with obstruction of the cystic duct from a stone. However, if the ultrasound does not demonstrate gallstones, the pain could be originating from other pathology (e.g., gastric or duodenal ulcer, pancreatitis, etc). Removing the gallbladder will not improve the patient's condition should other pathology be present that is not a gallbladder pathology.

A gallbladder scan (aka Hida scan) will show lack of filling of the gallbladder if cystic duct obstruction with acute cholecystitis is present. Then, a gallbladder emptying study can be performed. If the gallbladder does not empty normally, in response to the hormone cholecystokinin, there is a 90% chance of significant improvement and more likely cure of the abdominal pain with cholecystectomy. Thus, gallbladder filling and emptying studies are useful tests.

Liver masses

Category:Liver diseases may also be detected with careful imaging. Ultrasound is one inexpensive and readily available way to detect asymptomatic liver masses, including metastases, liver cell carcinoma (hepatoma), hepatic adenoma, focal nodular hyperplasia and hemangioma, most of which are benign.

Some benign lesions require open large sample biopsy with removal of a lot of the mass to make the diagnosis pathologically (e.g., focal nodular hyperplasia), though others such as hepatic cavernous hemangioma can bleed if a needle biopsy is performed, and often require urgen life-saving laparotomy to stop the bleeding. As such, biopsies and surgeries should not be performed asymptomatic people with a low likelihood of malignancy.

Cavernous hemangiomas can be proven non-invasively by labeling the patient's red blood cells and imaging the liver. Hemangiomas are intensely hot (concentrate radiolabelled red blood cells) whereas other lesions are not.