A Meckel scan is a nuclear medicine imaging test used to detect a Meckel’s diverticulum, a small pouch in the wall of the small intestine that some people are born with. The scan works by injecting a small amount of radioactive tracer into a vein, which gets absorbed by stomach-lining tissue. If that type of tissue exists where it shouldn’t (inside the pouch), it lights up on the camera. In children, the scan has a sensitivity of about 94% and specificity of 97%, making it the preferred noninvasive test for this condition.
What a Meckel’s Diverticulum Is
A Meckel’s diverticulum is a remnant of fetal development. During early pregnancy, a duct connects the developing intestine to the yolk sac. That duct normally disappears before birth, but in roughly 2% of people, a small bulge remains on the wall of the small intestine. Most people with one never know it exists. It only causes problems when the pouch contains tissue that doesn’t belong there, most commonly tissue identical to the lining of the stomach.
This misplaced stomach tissue produces acid just like it would in the actual stomach. But the small intestine isn’t built to handle acid, so the surrounding tissue can erode, bleed, or cause blockages. Younger children are more likely to develop symptoms than older children or adults. The classic presentation taught in medical training is painless rectal bleeding, but research shows that bowel obstruction is actually the more common reason young children end up in the emergency department with a symptomatic Meckel’s diverticulum. Symptoms can include abdominal pain, vomiting (sometimes green-tinged bile), lethargy, and decreased appetite.
How the Scan Detects the Problem
The tracer used in a Meckel scan is called technetium-99m pertechnetate. It behaves similarly to chloride in the body, meaning the acid-producing cells of stomach tissue naturally pull it out of the bloodstream and concentrate it. Normal stomach tissue in the upper abdomen will always light up on the scan. The key finding is a second bright spot lower in the abdomen, typically in the right lower quadrant, where stomach-type tissue shouldn’t exist.
This is what makes the test so targeted. It doesn’t image the pouch itself. It images the misplaced stomach lining inside the pouch. Because most symptomatic Meckel’s diverticula contain this ectopic gastric tissue, the scan is well suited to catching the cases that actually cause bleeding or other complications.
What to Expect During the Scan
You (or your child) will need to fast beforehand, typically for several hours, so the stomach and intestines are relatively empty. An IV line is placed, and the radioactive tracer is injected. After that, you lie flat on a table under a gamma camera, which captures images of your abdomen as the tracer circulates and concentrates in gastric tissue. The imaging portion generally takes about 30 to 60 minutes, with pictures taken at regular intervals to track how the tracer moves through the body.
The test is painless aside from the needle stick. The radiation dose is low, comparable to many standard diagnostic imaging tests. No sedation is usually required, though very young children who can’t stay still may need help remaining calm.
Medications That Improve Accuracy
Several medications can be given before the scan to make it more reliable. Acid-blocking drugs like cimetidine, ranitidine, or famotidine are the most common. These work by preventing the stomach-lining cells from releasing the tracer too quickly into the intestine, which keeps the abnormal tissue “bright” on the camera for longer. In children, proton pump inhibitors (a different class of acid blocker) are sometimes used instead because they’re easier to administer on short notice.
Glucagon is another option. It slows down the movement of the intestinal walls, which prevents the tracer from washing downstream before it can be captured on the image. Without these pretreatments, the tracer can disperse through the intestine and obscure the area of concern. Your medical team will decide which combination, if any, is appropriate.
Accuracy and Limitations
A large review of 183 pediatric cases found the scan achieved 94% sensitivity and 97% specificity for detecting ectopic gastric tissue. That means it correctly identifies the problem in the vast majority of cases and rarely flags something that isn’t there. Some sources report even higher accuracy when pretreatment medications are used properly.
False positives can occur. Several other conditions cause abnormal tracer uptake in the abdomen, including intestinal duplications (extra segments of bowel), Barrett’s esophagus, inflammatory bowel lesions, arteriovenous malformations, and certain bowel tumors. Abnormalities in the urinary tract can also interfere, since the tracer is excreted through the kidneys and bladder. A full bladder or kidney abnormality can mimic or mask a true positive result.
False negatives happen too, most often when a Meckel’s diverticulum doesn’t contain enough gastric tissue to absorb a detectable amount of tracer. If the pouch is inflamed, bleeding heavily, or contains a different tissue type (like pancreatic tissue instead of stomach tissue), the scan may miss it entirely. A negative Meckel scan doesn’t completely rule out the diagnosis, especially if symptoms are strongly suggestive.
Why It’s Ordered Instead of Other Tests
CT scans and ultrasounds can sometimes detect a Meckel’s diverticulum, but they do so inconsistently because the pouch can look like normal bowel. The Meckel scan’s advantage is that it identifies the specific tissue abnormality causing the symptoms rather than trying to spot a structural change. This makes it the preferred first-line imaging test when a doctor suspects a symptomatic Meckel’s diverticulum, particularly in children with unexplained gastrointestinal bleeding. If the scan is negative but clinical suspicion remains high, other imaging or even surgical exploration may follow.