Meckels Scan Test: Purpose, Test Details & Results

Purpose of Meckels Scan Test

When a child or young adult presents with unexplained gastrointestinal bleeding, one rare but important diagnosis to consider is Meckel’s diverticulum. The Meckel’s scan—also known as a technetium-99m pertechnetate scan—is a specialized nuclear medicine test designed to detect this abnormality. Understanding why and when this scan is used helps patients, families, and healthcare providers make informed decisions about care for gastrointestinal symptoms.

Table 1: Main Reasons for Ordering a Meckel's Scan

The Clinical Role of Meckel’s Scan

Meckel’s diverticulum is a congenital pouch found in the small intestine. While often silent, it may contain stomach-like tissue that secretes acid, leading to ulceration and bleeding—especially in children. The Meckel’s scan is primarily performed in patients who have:

• Unexplained gastrointestinal (GI) bleeding, especially if painless and from the rectum
• Unexplained anemia thought to be due to GI blood loss
• Persistent or recurrent abdominal pain when other causes have been ruled out
• Occasionally, infants with unexplained discharge or infection at the umbilicus, as this can rarely be due to a persistent connection related to Meckel’s diverticulum 1 2 3 4 5 6

Who Should Get This Test?

The test is most accurate and useful when:

• The patient is a child or adolescent with painless lower GI bleeding
• There is clinical suspicion of Meckel’s diverticulum, especially if the bleeding is significant enough to cause anemia 1 3 4 5
• Other causes of bleeding have been excluded, and the clinical presentation is suggestive (e.g., sudden dark or bright red blood per rectum without pain) 3 4

Limitations of the Scan’s Purpose

It’s important to note that the Meckel’s scan is less helpful for:

• Generalized abdominal pain without bleeding
• Children or adults without GI symptoms
• Confirming Meckel’s diverticulum if the scan is negative but suspicion remains very high 1 2 7

Meckels Scan Test Details

If you or your child is scheduled for a Meckel’s scan, knowing how the test works and what to expect can help ease anxiety. The scan is minimally invasive and generally well-tolerated, but it does require careful preparation and skilled interpretation for the best results.

Table 2: Steps Involved in a Meckel’s Scan

How the Test Works

The Meckel’s scan relies on a small amount of radioactive material called technetium-99m pertechnetate. This substance is injected into a vein (usually the arm). It accumulates in stomach tissue—both normal and misplaced (ectopic) tissue that can occur in Meckel’s diverticulum 1 3 4.

A gamma camera is then used to take pictures of the abdomen over about 30 to 60 minutes. If a Meckel’s diverticulum contains stomach-like (gastric) cells, the technetium will "light up" in that location, appearing as a bright spot distinct from the normal stomach 3 4 6.

Preparation for the Scan

For best results, patients may be asked to:

• Fast for several hours before the procedure
• Sometimes receive medications (such as cimetidine, glucagon, or pentagastrin) to improve the scan’s sensitivity by reducing the movement of technetium out of the gastric tissue 3 4 7
• Avoid certain medications or foods prior to testing as instructed by the care team

Safety and Comfort

• The test uses a small amount of radioactivity, which is considered safe for children and adults, with the benefits outweighing the minimal risk 1 3 4
• The injection may cause brief discomfort; otherwise, the test is painless
• Rarely, a repeat scan may be recommended if the first result is negative or unclear but suspicion remains high 7

Limitations and Possible Pitfalls

• Not all Meckel’s diverticula contain gastric tissue, so some cases can be missed (false negatives) 1 2 7
• Rarely, other conditions (such as bowel inflammation or duplication cysts) can cause false positives 3 6
• Proper patient preparation and scan technique are crucial for accuracy; poorly prepared scans may need to be repeated 3 7

Meckels Scan Test Results & Follow-Up

After the scan, interpreting the results and deciding next steps is key. The clinical team combines scan findings with symptoms and other test results to guide your care.

Table 3: Interpreting Meckel’s Scan Results

What Do the Results Mean?

Positive Scan
A bright spot outside the normal stomach area strongly suggests Meckel’s diverticulum with gastric tissue. This finding is highly predictive—especially in a child with bleeding—and surgery is usually recommended to remove the diverticulum and confirm the diagnosis 3 4 5.

Negative Scan
If the scan is negative but suspicion remains high (for example, ongoing unexplained GI bleeding), a repeat scan or direct surgical exploration may be needed. Sometimes, a negative scan truly means no Meckel’s diverticulum, but in rare cases, the diverticulum is present but does not contain enough gastric tissue to show up 1 2 7.

False Negatives and False Positives

• False negatives may occur if the Meckel’s diverticulum lacks gastric tissue or the scan technique/preparation was suboptimal. In such cases, repeated or alternative imaging—or direct surgical exploration—may be considered, especially if bleeding is severe 1 2 7.
• False positives are uncommon but can happen if other pathologies (like duplication cysts) take up the tracer 3 6.

Test Accuracy: Sensitivity, Specificity, and Predictive Value

• Sensitivity (correctly identifying those with the disease): Ranges from 60–100%, but is highest (up to 94–100%) in children with lower GI bleeding and anemia 1 3 4 5 6.
• Specificity (correctly identifying those without the disease): Typically above 90%, often 97% or higher 3 4 5 6.
• Positive Predictive Value: When the scan is positive in a child with GI bleeding, it is highly likely to be correct 3 4 5.
• Negative Predictive Value: A negative scan is usually reassuring, but not perfect—clinical judgement should guide further action if suspicion remains high 1 2 7.

What Happens After the Test?

• If positive: Surgery is recommended to remove the Meckel’s diverticulum, confirm the diagnosis, and prevent further bleeding 3 4 5.
• If negative but suspicion is high: Options include a repeat scan (especially if the first was done without optimal preparation), endoscopy, or sometimes exploratory surgery 1 2 7.
• If negative and symptoms resolve: No further action may be needed, but follow-up is important to ensure symptoms do not recur 3 5 6.

Conclusion

The Meckel’s scan is a valuable diagnostic tool—particularly in children with unexplained lower gastrointestinal bleeding. While highly accurate in many cases, it is not perfect, and clinical judgement remains essential. Here are the main takeaways:

• Meckel’s scans are best for evaluating unexplained GI bleeding in children, especially with anemia.
• The test involves a small injection of technetium-99m and imaging to detect gastric tissue in abnormal locations.
• Proper preparation and technique are vital for accurate results.
• A positive scan is highly predictive and usually leads to surgery; a negative scan does not always rule out disease if suspicion remains high.
• Repeat scans or alternative investigations may be needed in select cases.
• Work closely with your healthcare team to interpret results and decide on next steps.

With the right use, the Meckel’s scan can provide clarity and guide appropriate treatment for this challenging but treatable condition.