The Hidden Hitchhiker

When a Meckel's Diverticulum with Pancreatic Tissue Triggers Adult Intestinal Chaos

Introduction: An Abdominal Enigma

Most people associate intestinal emergencies with appendicitis or food poisoning, but deep within the small intestine, a forgotten embryonic remnant can unleash chaos.

Meckel's diverticulum—present in 2% of the population—is a silent time bomb that rarely detonates in adults. Even rarer is its transformation into a lead point for intussusception (a "telescoping" of the bowel), fueled by heterotopic pancreatic tissue—misplaced cells secreting corrosive enzymes. While pediatric cases dominate textbooks, a 45-year-old man's story of recurrent hematochezia (bright red rectal bleeding) reveals an adult-specific diagnostic labyrinth where standard tools fail, and overlooked tissues become dangerous actors 1 .

Did You Know?

Meckel's diverticulum is named after Johann Friedrich Meckel, who described its embryonic origin in 1809.

Quick Stats
  • Prevalence: 2% of population
  • Complication rate: 4-25% of cases
  • Adult presentations: Often misdiagnosed

Key Concepts: Embryonic Leftovers and Cellular Stowaways

Meckel's Diverticulum

A true diverticulum comprising all intestinal layers, Meckel's forms when the omphalomesenteric duct fails to regress during fetal development.

  • Location: 45-90 cm proximal to ileocecal valve
  • Ectopic Tissues: Gastric mucosa (62%), pancreatic tissue (6%) 8
  • Size Matters: >2 cm elevates complication risks 4
Heterotopic Pancreas

Defined as pancreatic tissue disconnected from the main organ, arising from pluripotential cell migration errors during development.

Heinrich Classification:
  1. Type 1: Acini, ducts, islets (most dangerous)
  2. Type 2: Ducts and acini only
  3. Type 3: Ducts alone
Intussusception

When Meckel's acts as a lead point, dragging proximal ileum into distal segments (ileoileal or ileocecal intussusception).

  • Adults account for <5% of cases 5 6
  • Often with pathologic lead points
  • Can be life-threatening if not treated
Clinical Insight

Adult presentations shift from childhood bleeding toward obstruction or inflammation, making intussusception exceptionally unusual past age 30 1 8 .

In-Depth Look: The Diagnostic Odyssey of an Adult Case

The Case: A 45-Year-Old Man's Recurrent Bleeding

A previously healthy adult presented with monthly hematochezia and no pain. Initial endoscopy and CT scans were normal. Hemoglobin dropped to 114 g/L, and stool tests confirmed occult bleeding. Standard Meckel's scintigraphy (Tc-99m pertechnetate) failed—likely due to absent gastric mucosa 1 .

Patient Timeline
  • Month 1: First episode of hematochezia
  • Month 3: Colonoscopy - normal findings
  • Month 5: CT scan - inconclusive
  • Month 6: DBE reveals Meckel's diverticulum
  • Month 7: Successful laparoscopic resection
Illustration of Meckel's diverticulum

Illustration showing Meckel's diverticulum in the small intestine.

Diagnostic Breakthrough: Double-Balloon Enteroscopy (DBE)

Methodology:

  1. Preparation: 12-hour fast; conscious sedation.
  2. Insertion: A flexible endoscope with an overtube and balloons alternates inflation to "walk" through the small bowel.
  3. Identification: At 100 cm proximal to the ileocecal valve, DBE revealed:
    • A "double duct sign" (pathognomonic for Meckel's).
    • An ulcer at the diverticulum's base 1 .
Results and Analysis

DBE detected the diverticulum missed by CT and scintigraphy. Biopsies confirmed heterotopic pancreatic tissue (Heinrich Type 1). This highlights DBE's superiority for adult small-bowel bleeding where gastric mucosa is absent 1 .

Diagnostic Modalities Compared

Method Sensitivity in Adults Limitations
Tc-99m scan 25-50% Requires gastric mucosa
CT enterography 30-45% Low for flat lesions
DBE 70-90% Invasive, operator-dependent
Capsule endoscopy 60-75% Risk of retention in strictures
Table 1: Diagnostic Modalities Compared 1 8
Diagnostic Sensitivity Comparison
Surgical Outcomes
Complication Resolution Rate Recurrence Risk
Bleeding 98% <2%
Intussusception 95% 5%
Perforation 85% 10-15%
Table 2: Surgical Outcomes in Adult Meckel's Cases 1 6 8

Surgical Resolution: Laparoscopic Resection

The diverticulum (3 cm × 2 cm) was resected with adjacent ileum. Pathology validated pancreatic acini, ducts, and islets within the diverticulum wall. The ulcer (0.5 cm × 0.6 cm) confirmed acid-independent erosion from pancreatic enzymes 1 .

Surgical Approach
  • Laparoscopic resection
  • Segmental ileal resection
  • Primary anastomosis
Post-Op Outcomes
  • Hospital stay: 3 days
  • Full recovery: 2 weeks
  • No recurrence at 1 year
Essential Reagents
Reagent Application
Tc-99m pertechnetate Detects ectopic gastric mucosa
Anti-chromogranin antibodies Confirms pancreatic islets
HE stain Classifies Heinrich types
Table 3: Essential Reagents 1 4

Conclusion: A Call for Vigilance in Adult GI Mysteries

Once deemed a pediatric oddity, Meckel's diverticulum with heterotopic pancreas is emerging as a stealthy adult adversary. As showcased by the 45-year-old's ordeal, advanced endoscopy and imaging are rewriting diagnostic playbooks.

For clinicians, the takeaway is clear: in unexplained lower GI bleeding, think beyond the usual suspects—a hidden pancreatic hitchhiker may be the culprit 1 .

"The abdomen is a Pandora's box of embryonic secrets. In adults, Meckel's diverticulum isn't just a relic—it's a landmine."

Adapted from Surgical Chronicles (2025)

References