What is Meckel's diverticulum in a patient under 40 with chronic gastrointestinal blood loss and negative GI and stool workups?

Meckel's Diverticulum: Definition and Clinical Significance

Meckel's diverticulum is the most common congenital malformation of the gastrointestinal tract, present in approximately 2% of the population, representing a remnant of the vitelline duct that appears as a true diverticulum containing all layers of the intestinal wall located on the antimesenteric border of the distal ileum. 1, 2, 3

Anatomical Characteristics

• True diverticulum structure: Contains all intestinal wall layers including muscularis propria, distinguishing it from acquired diverticula 1, 2
• Location: Found on the antimesenteric border of the distal ileum, typically within 60-100 cm of the ileocecal valve 2
• Embryological origin: Results from incomplete obliteration of the vitelline (omphalomesenteric) duct during fetal development 3

Clinical Presentations in Your Patient Population

In patients under 40 years old with chronic gastrointestinal blood loss, Meckel's diverticulum is a critical diagnostic consideration, as younger patients are more likely to have Meckel's diverticulum and Dieulafoy's lesion as causes of obscure bleeding compared to older patients who typically have vascular lesions. 4, 5

Bleeding Manifestations

• Painless rectal bleeding is the classic presentation, particularly in younger patients and children 1, 6
• Bleeding occurs in 99 of 233 symptomatic pediatric patients in one series, making it the most common symptomatic presentation 6
• Mechanism: Ectopic gastric mucosa within the diverticulum (present in 154 of 286 patients in one series) secretes acid that ulcerates adjacent ileal mucosa, causing hemorrhage 6
• Can present as occult blood loss leading to iron deficiency anemia or as overt melena/hematochezia 7, 6

Other Complications (Less Relevant to Your Scenario)

• Intestinal obstruction from intussusception, volvulus around fibrous bands, or adhesions 6, 8
• Diverticulitis mimicking appendicitis 6, 3
• Perforation with peritonitis 6, 3
• Neoplastic transformation (rare) 2

Diagnostic Approach for Your Clinical Scenario

When upper endoscopy and colonoscopy are negative in a patient under 40 with chronic gastrointestinal blood loss, a Meckel's scan using Tc-99m pertechnetate scintigraphy is the diagnostic test of choice, with sensitivity of 89% and specificity of 98% for detecting symptomatic Meckel's diverticulum. 4, 1

Imaging Strategy

• Meckel's scan (Tc-99m pertechnetate): Detects ectopic gastric mucosa by accumulating in gastric parietal cells, creating a fixed focal area of uptake 1

  • Highest diagnostic accuracy when the patient has GI bleeding with anemia 1
  • Positive predictive value approaches 100% in anemic patients with GI bleeding 1
  • In one pediatric series, 55 of 78 scans (71%) were positive in patients with bleeding 6

• CT enterography: Alternative when bleeding is not active or Meckel's scan is negative, can identify the diverticulum and exclude other small bowel pathology 1

• Capsule endoscopy: Should be performed for comprehensive small bowel evaluation when initial endoscopic workup is negative, as it identifies bleeding sources in 55-65% of patients with obscure bleeding 4

Critical Diagnostic Pitfalls

Inverted Meckel's diverticulum can present as occult lower GI hemorrhage and is increasingly recognized (19 cases reported 2006-2012 vs. <40 cases from 1978-2005), requiring high clinical suspicion as it may be missed on standard imaging including Meckel's scans. 7

• Standard Meckel's scans can be falsely negative in 23 of 78 cases (29%) even in symptomatic bleeding patients 6
• Inverted diverticula may appear as intraluminal masses or intussusception on CT imaging 7
• Most symptomatic Meckel's diverticula with bleeding occur in children and young adults, making age a key diagnostic clue 1

Management Implications

Surgical resection is the definitive treatment for symptomatic Meckel's diverticulum, with laparoscopy becoming the preferred approach for both diagnosis and treatment. 6, 3

• Segmental resection of the diverticulum with primary anastomosis is standard 6, 8
• Incidentally found Meckel's diverticulum during surgery for other indications should be removed, as ectopic tissue is the main cause of future complications 6
• Delayed diagnosis leads to significant morbidity and mortality, particularly when complications like perforation or gangrene develop 8, 3