Approach to Gastrointestinal Imaging

Approach to Gastrointestinal Imaging

Main Text


Nuclear gastrointestinal imaging comprises functional studies of the stomach, liver, gallbladder, and spleen, as well as localizing the source of GI bleeding and abdominopelvic infection. These studies provide a useful adjunct to anatomic imaging in complicated cases and are often the standard of care for optimal clinical management in patients with chronic abdominal pain, occult infection, and GI bleeding.

Imaging Protocols

Gastric Emptying

Symptoms of postprandial nausea, bloating, and abdominal pain can be caused by gastric emptying that is too fast or too slow. In patients with gastroparesis, gastric emptying studies using Tc-99m sulfur colloid in a standardized egg sandwich meal can confirm the diagnosis as well as evaluate the efficacy of prokinetic agents. Interestingly, in one study, 23% of patients with suspected gastroparesis actually showed rapid gastric transit on a nuclear gastric emptying study, even though they had not undergone a surgery that could cause dumping syndrome. Recent studies suggest abnormal emptying of solids &/or liquids can cause symptoms of gastroparesis. A dual-radiotracer technique (Tc-99m sulfur colloid in an egg sandwich and In-111 DTPA in water) is now being performed, showing coincident solid and liquid emptying during the same four-hour study. Liquid gastric emptying studies are used in pediatric patients with feeding difficulties/failure to thrive and in adult and pediatric patients with feeding tubes. The value of these studies often lies in determining the timing of when a patient’s stomach empties, so that feeding schedules can be optimized.

Biliary Patency and Function

In patients with acute right upper quadrant (RUQ) pain, US can have a sensitivity as low as 54% for acute cholecystitis. Assessing patency of the cystic duct and common bile duct using Tc-99m IDA derivatives offers valuable clinical information early in the disease course, when outcomes can be optimized with early cholecystectomy. Patients with chronic intermittent RUQ pain and a patent biliary system can have acalculous cholecystopathy or gallbladder dyskinesia. Defined as a gallbladder ejection fraction 35-38% on hepatobiliary scan, patients with gallbladder dyskinesia can be triaged to laparoscopic cholecystectomy with symptomatic relief 94-98% of the time. In patients with gallbladder ejection fraction > 80%, gallbladder hyperkinesia or excessive contractility may also be an indication for cholecystectomy, and limited studies show these patients have symptomatic relief post surgery.

After laparoscopic cholecystectomy, the incidence of bile leak can be as high as 4% (higher than the traditional rate with open cholecystectomy). After surgery, hepatobiliary scans become useful in patients with postoperative pain to diagnose biliary leak or biloma. In addition, enterogastric bile reflux, a complication of gallbladder and gastric surgery that causes postoperative abdominal pain, can be seen on hepatobiliary scan.

Liver and Spleen Imaging

Although anatomic imaging with US, CT, and MR characterizes the vast majority of abdominal lesions, a small percentage remain indeterminate. To avoid liver biopsy, Tc-99m IDA derivatives, Tc-99m sulfur colloid, and Tc-99m RBC scans can diagnose focal nodular hyperplasia, hepatic adenomas, and hemangiomas, particularly in lesions > 2 cm. Similarly, ectopic splenic tissue can be diagnosed using Tc-99m heat-damaged RBC scans, avoiding biopsy if confused with cancer recurrence and directing surgery in patients with recurrent idiopathic thrombocytopenic purpura post splenectomy. Radiotracer-based localization of splenic tissue remains important in infants with certain congenital anomalies, as US can be inconclusive and insensitive in this clinical scenario. In these patients, the presence or absence of splenic tissue directs antibiotic therapy and offers information on projected lifespan.

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May 7, 2023 | Posted by in CARDIOVASCULAR IMAGING | Comments Off on Approach to Gastrointestinal Imaging

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