A 30-year-old man comes to the emergency department due to severe abdominal pain. The patient first developed the pain yesterday, and it has become increasingly worse. Over the last few hours, he has also developed bilious emesis. The patient has had no previous surgeries. Temperature is 37.8 C (100 F) and pulse is 110/min. Physical examination shows diffuse abdominal tenderness with guarding during palpation. Abdominal imaging reveals bowel wall thickening within a blind pouch connected to the ileum. A laparotomy is performed. During the procedure, a fibrous band is seen attaching the end of the pouch to the umbilicus. The walls of this pouch are most likely composed of which of the following?
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This patient's outpouching from the ileum with a fibrous band connected to the umbilicus is characteristic of a Meckel diverticulum.
This congenital anomaly is due to incomplete obliteration of the vitelline (omphalomesenteric) duct in utero; the duct normally serves as a communication between the yolk sac and the primitive midgut in early gestation. Meckel diverticulum is typically located in the small bowel 2 feet from the ileocecal valve and, if symptomatic, often presents by age 2 (ie, rule of 2s); however, it can cause complications at any age.
Meckel diverticulum is a true diverticulum, consisting of all 3 layers of the intestinal wall: mucosa, submucosa, and muscularis. It often contains heterotopic gastric mucosa, which secretes hydrochloric acid and leads to the classic presentation of painless lower gastrointestinal bleeding (hematochezia) due to the ulceration of adjacent intestine. Patients may also develop diverticular inflammation with signs of acute intestinal obstruction (eg, abdominal pain, guarding, bilious emesis), as seen in this patient. Other complications of a Meckel diverticulum can include intussusception, volvulus, and bowel perforation.
(Choice A) Fibrous scar tissue, which can be present postoperatively or due to chronic inflammation, can cause intestinal obstruction with severe abdominal pain, bilious emesis, and guarding. However, a blind pouch connected to the ileum with an attachment to the umbilicus would not be present.
(Choice B) Granulation tissue is new connective tissue that forms in response to wound healing, and the peritoneum is the lining of the abdominal cavity. These tissues are not contained in a Meckel diverticulum.
(Choice C) False diverticula contain only mucosa and submucosa. These layers herniate through defects in the muscular layer. Colonic and Zenker (upper esophageal) diverticula are examples of false diverticula.
(Choice D) Tumors of the omentum (ie, adipose tissue covering the abdominal organs) are a rare cause of abdominal pain and vomiting but are not associated with an outpouching of the ileum.
Educational objective:
Meckel diverticulum, which classically causes painless hematochezia but can present with acute abdominal pain if inflamed (ie, diverticulitis), is an anatomic connection between the ileum and umbilicus resulting from incomplete obliteration of the vitelline duct. This congenital anomaly is a true diverticulum, consisting of all 3 layers of the intestinal wall (mucosa, submucosa, and muscularis).