Meckel’s diverticulum study

The Meckel’s Diverticulum Study, also referred to as a Meckel’s Scan, is a specialized nuclear medicine test used to detect the presence of ectopic gastric mucosa in the small intestine, typically within a Meckel's diverticulum. This test is especially valuable in diagnosing the cause of unexplained gastrointestinal bleeding, especially in young children and adolescents. Meckel’s diverticulum is a congenital pouch (true diverticulum) found in the small intestine, present in approximately 2% of the population. It may contain functioning gastric mucosa, which secretes acid, potentially causing ulceration and bleeding in the adjacent intestinal tissue.

The scan uses Technetium-99m pertechnetate (99mTc), a radiopharmaceutical that selectively accumulates in gastric mucosa. When injected intravenously, it enables the visualization of ectopic mucosal tissue through gamma camera imaging, thereby identifying the source of occult or intermittent GI bleeding.

What is Meckel's Diverticulum?

1. Meckel’s diverticulum is a congenital anomaly resulting from the incomplete obliteration of the vitelline duct (omphalomesenteric duct).
2. It is usually located within 2 feet of the ileocecal valve on the antimesenteric border of the ileum.
3. While often asymptomatic, a Meckel’s diverticulum may cause complications, especially if it contains ectopic gastric or pancreatic tissue.
4. Gastric mucosa can secrete acid, leading to ulceration, inflammation, and bleeding in adjacent bowel regions.
5. The condition is most commonly identified in children under the age of 10, though adults can also be affected.

Why is the Meckel's Diverticulum Scan Performed?

1. To detect ectopic gastric mucosa in a suspected Meckel's diverticulum.
2. To localize the source of unexplained gastrointestinal bleeding, especially when endoscopy or colonoscopy fails to identify the cause.
3. To evaluate recurrent melena (black stools) or hematochezia (fresh blood in stools) in children.
4. To avoid invasive surgical exploration by providing accurate anatomical localization.
5. To guide surgical management in symptomatic Meckel’s diverticulum.

Indications for Meckel’s Scan

1. Recurrent or unexplained lower GI bleeding in pediatric patients.
2. Iron-deficiency anemia due to chronic occult bleeding.
3. Abdominal pain with suspected gastrointestinal tract anomalies.
4. Negative findings in endoscopy and colonoscopy despite persistent bleeding.
5. Evaluation of intermittent melena or rectal bleeding without trauma.

How is the Meckel’s Diverticulum Scan Performed?

1. The patient is positioned comfortably under a gamma camera for imaging.
2. A small intravenous dose of 99mTechnetium pertechnetate is administered.
3. The tracer is selectively taken up by the gastric mucosa, including any ectopic mucosa.
4. Dynamic imaging begins immediately and continues for approximately 30 to 60 minutes.
5. The gamma camera captures sequential images of the abdomen, monitoring tracer distribution.
6. An abnormal focal uptake in the right lower abdomen indicates a Meckel’s diverticulum containing gastric mucosa.
7. In some cases, delayed images or pharmacological adjuncts (such as pentagastrin, cimetidine, or glucagon) may be used to improve diagnostic accuracy.

Preparation for the Test

1. Fasting for at least 4–6 hours before the scan is generally required.
2. Any medications that affect gastric secretion or GI motility (e.g., H2 blockers or antacids) may need to be temporarily discontinued under medical guidance.
3. The patient must inform the clinician of any allergies, recent GI infections, or previous nuclear medicine scans.
4. In pediatric patients, distraction techniques or mild sedation may be used if the child is anxious or uncooperative.

Benefits of the Meckel’s Scan

1. Non-invasive and painless procedure with no need for anesthesia or surgery.
2. Provides functional imaging of gastric mucosa—not just structural information.
3. Can detect small or intermittent sources of bleeding often missed by other modalities.
4. Helps localize bleeding before surgery, aiding in precise resection.
5. Low radiation exposure, making it safe for children and repeat studies if necessary.

Limitations of the Scan

1. False negatives may occur if the ectopic mucosa is absent or too small to detect.
2. False positives can be caused by urinary tract activity, bowel inflammation, or vascular anomalies.
3. Not all Meckel’s diverticula contain gastric mucosa, which is necessary for detection with 99mTc.
4. May not identify non-bleeding or fibrotic diverticula.
5. May require adjunct imaging or surgical exploration in inconclusive cases.

Who Interprets the Scan?

The Meckel’s scan is interpreted by a nuclear medicine physician or radiologist with experience in gastrointestinal imaging. The final report highlights:

1. Presence or absence of abnormal radiotracer uptake.
2. Localization of suspected Meckel’s diverticulum.
3. Recommendation for further testing or surgical intervention, if needed.

Post-Test Instructions

1. The patient may resume normal activity and diet unless otherwise instructed.
2. Increase fluid intake to help flush out any remaining tracer.
3. Results are typically available within 24 hours and shared with the referring doctor.
4. If bleeding continues despite a negative scan, other modalities may be pursued.

Conclusion

The Meckel’s Diverticulum Scan is a highly valuable nuclear medicine test designed to detect ectopic gastric mucosa, which is often responsible for unexplained GI bleeding in children and young adults. Using a simple and non-invasive radioactive tracer (99mTc-pertechnetate), the test provides real-time imaging of gastric mucosal uptake in abnormal locations, most notably in Meckel’s diverticulum. Its advantages include high sensitivity (when gastric mucosa is present), minimal discomfort, and the ability to guide surgical intervention when needed. When other modalities like endoscopy or colonoscopy fail to provide answers, the Meckel’s scan can play a decisive role in diagnosis and management, reducing patient suffering and preventing complications.

Early identification and localization of Meckel’s diverticulum through this test can significantly improve outcomes, particularly in pediatric patients where timely intervention is critical.