2. Meckel diverticulum:
failure of closure of the omphalomesenteric duct in the embryo.
The duct connects the yolk sac to the primitive foregut through the
umbilical cord. It is considered the most common structural congenital anomaly
of the gastrointestinal tract.
Approximately 1-3% of population may have a Meckel diverticulum, have
increased male predilection, it may occur with equal frequency in both sexes
although symptoms from complications are more common in male patients.
3. Meckel diverticulum is the most common and clinically important form of
heterotopic gastric mucosa. Although ectopic gastric mucosa is the
terminology frequently used, this is not really correct.
Ectopic refers to an organ that has migrated—for example, an ectopic
kidney.
Heterotopic refers to a tissue at its site of origin.
Causes of heterotopic gastric mucosa:
1.Meckel diverticulum.
2. Gastrointestinal duplications.
3. Postoperative retained gastric antrum.
4. Barrett esophagus.
4. Mechanism of Uptake
The mucosa of the gastric fundus contains multiple cell types including:
Parietal cells that secrete hydrochloric acid.
Chief cells that secrete pepsinogen and intrinsic factor.
The gastric Fundus, antrum and pylorus contain:
- G cells that secrete the hormone gastrin.
- Parietal cells were originally thought to be solely responsible for gastric uptake and
secretion of Tc-99m pertechnetate.
5. This is a true diverticulum that arises on the antimesenteric side of the small bowel,
approximately 80 to 90 cm proximal to the ileocecal valve. It is usually 2 to 3 cm in
size but may be larger.
Gastric mucosa is present in 10% to 30% of patients with Meckel diverticulum.
In 60% of symptomatic patients with the diverticulum, and in 98% of those with
bleeding.
More than 60% percent of patients with complications of Meckel diverticulum are
under age 2. Bleeding after age 40 is uncommon.
True diverticulum
6. Clinical presentation
A large proportion of individuals remain asymptomatic although up to a third of them may experience
clinical symptoms. There is an increased incidence of the Meckel diverticulum in Crohn patients compared
to the general population:
1.Gastrointestinal hemorrhage (melena/hematochezia): most common complication and
may account for ~30% of symptomatic cases.
2.Small-bowel obstruction: second most common presentation adhesion or mesodiverticular
band luminal obstruction
3. Volvolus.
4.Intussusception: particularly if the diverticulum inverts.
5.Internal hernia: from a persistent attachment of the diverticulum to the umbilicus by the
obliterated omphalomesenteric duct.
7. Radiographic features
Imaging these may occasionally be detected incidentally or may be identified if there is a
complication.
Fluoroscopy
Small bowel enemas have sometimes been used for the diagnosis in some centers, although a
precise technique is required if the diagnosis is to be excluded with any degree of certainty.
CT
CT is of limited value in uncomplicated cases, as the diverticulum may resemble a normal
bowel loop.
CT may show a fluid- or air-filled blind-ending pouch that arises from the antimesenteric side
of the distal ileum.
8. Angiography or CT angiography
When investigated in the context of gastrointestinal hemorrhage, angiography/CT
angiography may show the persistent omphalomesenteric artery in most individuals with a
Meckel diverticulum although recognition of the artery may be difficult due to overlying
vessels.
Scintigraphy
Scintigraphy with 99mTc-Na-pertechnetate has a limited sensitivity (~60%); however, it
aids in the diagnosis of diverticula with ectopic gastric mucosa.
Higher sensitivity may be present in children (~85-90%).
9. Methodology
Patient Preparation
- Fasting 4 to 6 hours before study to reduce size of stomach
- No pretreatment with sodium perchlorate; may be given after completion of study.
- No barium studies should be performed within 3 to 4 days of scintigraphy.
- Void before, during if possible, and after study.
Premedication
Cimetidine: 20 mg/kg/day orally for 48 hours in divided doses (or) Intravenous: 300 mg in 100 mL 5% dextrose
over 20 minutes; imaging begins 1 hour later.
(or)
Ranitidine: 2 mg/kg twice daily (or) Intravenous: 1 mg/kg (maximum 50 mg) intravenously over 20 minutes;
imaging begins 1 hour later
(or)
Famotidine: 0.5 mg/kg once daily × 48 hours Intravenous: 0.25 mg/kg intravenously 1 hour before procedure
11. Instrumentation
• Gamma camera: Large field of view
• Collimator: Low energy, all purpose or
high resolution
Imaging Procedure
• Obtain flow images: 60 1-second
frames.
• Obtain static images: 500k-counts for
first image, others for
• same time every 5 to 10 minutes for 1
hour.
• Erect, right lateral, posterior, or
oblique views. Obtain post-void image.
may be helpful at 30 to 60 minutes.
Patient Position
Position patient supine under camera with
xiphoid to symphysis pubis in field of view.
12. Image Interpretation
On the scan, a Meckel diverticulum appears as a focal area of increased
activity, usually in the right lower quadrant (see Fig. 10.37).
Tc-99m pertechnetate uptake is seen within 5 to 10 minutes after
injection and increases over time, typically at a rate similar to that of
gastric uptake.
Lateral or oblique views can help confirm the anterior position of the
diverticulum versus the posterior location of renal or ureteral activity.
Upright views may distinguish fixed activity (e.g., duodenum) from
heterotopic gastric mucosa, which moves inferiorly, and also renal
pelvic activity.
The intensity of activity may fluctuate because of intestinal secretions,
hemorrhage, or increased motility washing out radiotracer.
Post-void images can empty the renal collecting system and aid in
better visualization of areas adjacent to
the bladder.
13. Differential Diagnosis:
• Meckel diverticulum: A persistent focus in the RLQ whose uptake follows that
of the mucosa in the stomach is the most likely etiology, given the history.
• Duplication cyst: A known potential false-positive, this is less likely, given
the typical location of a Meckel diverticulum in the RLQ and the history.
• Ectopic renal pelvis: Another potential false-positive, this is less likely
because the timing of tracer uptake in this lesion follows the stomach, not the
urinary system.
14. Essential Facts:
• Found in 2% of the population
• Presents around 2 years of age
• Is twice as common in males
• Is 2 inches in size, 2 feet from the ileocecal valve
• Only 20% contain gastric mucosa.
• Only those that contain gastric mucosa will be seen on a Meckel scan,
and only those will typically bleed.
• Other manifestations of a Meckel diverticulum: include pain, perforation,
and intussusception/obstruction.
• Treatment is surgery.
15. (“Meckel scan”) demonstrates an abnormal and persistent focus in the right lower
quadrant (RLQ), which begins to appear at the same time as normal mucosal activity in the
stomach (arrow).
17. The scan shows faint focal uptake in the right upper-mid abdomen on the 5, 10, 15, 20 and 25-minute
delayed images (yellow arrows), consistent for Meckel diverticulum.
