Why does Meckel's diverticulum bleed?

Why Meckel's Diverticulum Bleeds

Meckel's diverticulum bleeding primarily occurs due to acid secretion from ectopic gastric mucosa causing ulceration of adjacent ileal mucosa, leading to erosion of blood vessels and subsequent hemorrhage.

Pathophysiology of Bleeding

Meckel's diverticulum is the most common congenital abnormality of the gastrointestinal tract, and its bleeding mechanism involves several key factors:

1. Ectopic Tissue Presence:

   • Approximately 50% of Meckel's diverticula contain ectopic tissue 1
   • Gastric mucosa is present in 60-85% of cases 1
   • Pancreatic tissue is found in 5-16% of cases 1

2. Acid Secretion Mechanism:

   • The ectopic gastric mucosa secretes acid
   • This acid erodes the adjacent normal ileal mucosa, which lacks protective mechanisms against acid
   • The resulting ulceration leads to erosion of blood vessels

3. Bleeding Characteristics:

   • Typically presents as painless, bright red rectal bleeding
   • Can be severe enough to require blood transfusion (67% of pediatric bleeding cases) 2
   • Often intermittent in nature

Diagnostic Considerations

When Meckel's diverticulum bleeding is suspected:

• Meckel Scan: The most useful diagnostic method using technetium-99m pertechnetate, which is taken up by the ectopic gastric mucosa 3, 1

  • The technique involves intravenous administration of 99mTc pertechnetate
  • Dynamic scintigraphy is performed for 30-60 minutes
  • Identifies fixed abdominal region of ectopic gastric mucosa 3
  • Has a diagnostic sensitivity of 85% in pediatric patients 2

• Other Imaging: CT enterography may help detect Meckel's diverticulum but is less specific than nuclear medicine scans 3

Clinical Presentation Patterns

Meckel's diverticulum bleeding typically presents in specific ways:

• Most symptomatic cases occur in children and young adults 3
• Presents as unexplained gastrointestinal bleeding without pain 1
• Can mimic other conditions like Crohn's disease, appendicitis, or peptic ulcer disease 1
• May be exacerbated by NSAIDs (as seen in a case report where bleeding occurred after acetylsalicylic acid ingestion) 4

Risk Factors for Bleeding

Certain factors increase the likelihood of bleeding from a Meckel's diverticulum:

• Presence of ectopic gastric mucosa (found in 88% of symptomatic cases) 2
• Young age (more common in pediatric population)
• Male gender (pediatric studies show male predominance with 120 boys vs 44 girls) 2
• Anatomical factors such as fibrous bands to umbilicus or mesentery 2

Management Implications

Understanding the bleeding mechanism guides management:

• Surgical resection is the definitive treatment 1
• Laparoscopic approach is feasible and effective 4
• Diagnostic laparotomy is considered the most sensitive test for Meckel's diverticulum when other investigations are inconclusive 3

Clinical Pitfalls

Important considerations to avoid misdiagnosis:

• Meckel's diverticulum bleeding can be mistaken for other causes of lower GI bleeding
• Negative upper and lower endoscopy with persistent bleeding should raise suspicion
• Consider Meckel's diverticulum in any patient with unexplained rectal bleeding, especially children and young adults
• Pertechnetate scans may be falsely negative if the diverticulum lacks gastric mucosa

Understanding the mechanism of bleeding in Meckel's diverticulum is crucial for prompt diagnosis and appropriate management, particularly in cases of unexplained gastrointestinal bleeding where standard endoscopic evaluations are negative.