DOI: 10.1148/rg.242035187
RadioGraphics 2004;24:565-587
From the Archives of the AFIP
Meckel Diverticulum: Radiologic Features with Pathologic Correlation1
Angela D. Levy, LTC, MC, USA and
Christine M. Hobbs, MD
1 From the Departments of Radiologic Pathology (A.D.L.) and Hepatic and Gastrointestinal Pathology (C.M.H.), Armed Forces Institute of Pathology, 6825 16th St NW, Washington, DC 20306-6000; and the Department of Radiology and Nuclear Medicine, Uniformed Services University of the Health Sciences, Bethesda, Md (A.D.L.). Received August 28, 2003; accepted October 7. Both authors have no financial relationships to disclose. Address correspondence to A.D.L. (e-mail: levya@afip.osd.mil).
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Abstract
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Meckel diverticulum is the most common congenital anomaly of the gastrointestinal tract, occurring in 2%–3% of the population. It results from improper closure and absorption of the omphalomesenteric duct. Meckel diverticulum is the most common end result of the spectrum of omphalomesenteric duct anomalies, which also include umbilicoileal fistula, umbilical sinus, umbilical cyst, and a fibrous cord connecting the ileum to the umbilicus. The formation of Meckel diverticulum occurs with equal frequency in both sexes, but symptoms from complications are more common in male patients. Sixty percent of patients come to medical attention before 10 years of age, with the remainder of cases manifesting in adolescence and adulthood. Heterotopic gastric and pancreatic mucosa are frequently found histologically within the diverticula of symptomatic patients. The most common complications are hemorrhage from peptic ulceration, small intestinal obstruction, and diverticulitis. Although the clinical, pathologic, and radiologic features of the complications of Meckel diverticulum are well known, the diagnosis of Meckel diverticulum is difficult to establish preoperatively.
Index Terms: Enteritis, 742.274 • Intestines, diverticula, 742.1493 • Intestines, hemorrhage, 95.7181 • Intestines, stenosis or obstruction, 742.723 Intussusception, 742.73
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LEARNING OBJECTIVES FOR TEST 6
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After reading this article and taking the test, the reader will be able to:
- Describe the embryologic and clinical features of Meckel diverticulum.
- Identify the pathologic and radiologic features of complications of Meckel diverticulum.
- Discuss the radiologic evaluation of patients with suspected Meckel diverticulum.
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Introduction
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Meckel diverticulum is the most common congenital anomaly of the gastrointestinal tract, occurring in 2%–3% of the population (1). Originally described in 1809 by the German anatomist, Johann Friedrich Meckel (1781–1833), the diverticulum is the result of incomplete atrophy of the omphalomesenteric duct (2). Occurring on the antimesenteric border of the distal ileum, Meckel diverticulum is a true diverticulum, composed of all layers of the intestinal wall, and is lined by normal small intestinal mucosa. It frequently contains heterotopic gastric and pancreatic mucosa and less commonly, duodenal, colonic, or biliary mucosa.
Clinical symptoms arise from complications of the diverticulum such as peptic ulceration with hemorrhage; diverticulitis; intestinal obstruction from diverticular inversion, intussusception, volvulus, torsion, or inclusion of the diverticulum in a hernia; formation of enteroliths; and development of neoplasia within the diverticulum. Although most complications manifest during childhood, they may occur during adult life as well. The preoperative diagnosis of a complicated Meckel diverticulum can be challenging and is often difficult to establish. The challenge is especially true in many adult patients because the clinical symptoms and imaging features of a complicated Meckel diverticulum overlap with those of many other disorders that cause acute abdominal pain or gastrointestinal bleeding. The purpose of this article is to review the embryologic, clinical, pathologic, and radiologic features of Meckel diverticulum with an emphasis on radiologic-pathologic correlation.
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Embryologic Features
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The omphalomesenteric (vitelline) duct is the embryonic communication between the yolk sac and the developing midgut. During the 6th week of embryogenesis, the midgut elongates and herniates into the umbilical cord. Within the umbilical cord, the midgut rotates 90° counterclockwise around the axis of the superior mesenteric artery. At the same time, the midgut elongates to form the jejunum and ileum and the lumen of the omphalomesenteric duct closes. By the 10th week of embryogenesis, the midgut returns to the abdominal cavity and the omphalomesenteric duct becomes a thin fibrous band, which eventually disintegrates and is absorbed (3). The omphalomesenteric duct will continue to grow if it fails to completely atrophy and disintegrate.
Incomplete atrophy of the omphalomesenteric duct may result in a variety of anomalies: umbilicoileal fistula, omphalomesenteric duct sinus, omphalomesenteric duct cyst, fibrous connection of the ileum to the umbilicus, or Meckel diverticulum (Fig 1). Umbilicoileal fistula results from a completely patent omphalomesenteric duct and is the least common of these anomalies. The duct remains open through its entire course (Fig 1a). Patients usually come to clinical attention in the newborn period because of fecal drainage from the umbilicus (3). Ileoileal intussusception into the patent duct may occur, appearing clinically as ileal prolapse at the umbilicus (4).
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Figure 1a. Drawings illustrate the spectrum of anomalies resulting from incomplete atrophy of the omphalomesenteric duct. (a) Umbilicoileal fistula is a completely patent omphalomesenteric duct connecting the ileum to the anterior abdominal wall at the umbilicus. (b) Umbilical sinus results from failure of the umbilical end of the omphalomesenteric duct to close. (c) Umbilical cyst occurs when the midportion of the duct remains patent and each end obliterates. (d) A persistent fibrous cord occurs when the duct obliterates but is not absorbed. (e, f) Meckel diverticulum results when the ileal end of the duct remains patent and the umbilical end atrophies. The diverticulum remains connected to the umbilicus by a fibrous band if the obliterated duct fails to be absorbed (e).
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Figure 1b. Drawings illustrate the spectrum of anomalies resulting from incomplete atrophy of the omphalomesenteric duct. (a) Umbilicoileal fistula is a completely patent omphalomesenteric duct connecting the ileum to the anterior abdominal wall at the umbilicus. (b) Umbilical sinus results from failure of the umbilical end of the omphalomesenteric duct to close. (c) Umbilical cyst occurs when the midportion of the duct remains patent and each end obliterates. (d) A persistent fibrous cord occurs when the duct obliterates but is not absorbed. (e, f) Meckel diverticulum results when the ileal end of the duct remains patent and the umbilical end atrophies. The diverticulum remains connected to the umbilicus by a fibrous band if the obliterated duct fails to be absorbed (e).
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Figure 1c. Drawings illustrate the spectrum of anomalies resulting from incomplete atrophy of the omphalomesenteric duct. (a) Umbilicoileal fistula is a completely patent omphalomesenteric duct connecting the ileum to the anterior abdominal wall at the umbilicus. (b) Umbilical sinus results from failure of the umbilical end of the omphalomesenteric duct to close. (c) Umbilical cyst occurs when the midportion of the duct remains patent and each end obliterates. (d) A persistent fibrous cord occurs when the duct obliterates but is not absorbed. (e, f) Meckel diverticulum results when the ileal end of the duct remains patent and the umbilical end atrophies. The diverticulum remains connected to the umbilicus by a fibrous band if the obliterated duct fails to be absorbed (e).
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Figure 1d. Drawings illustrate the spectrum of anomalies resulting from incomplete atrophy of the omphalomesenteric duct. (a) Umbilicoileal fistula is a completely patent omphalomesenteric duct connecting the ileum to the anterior abdominal wall at the umbilicus. (b) Umbilical sinus results from failure of the umbilical end of the omphalomesenteric duct to close. (c) Umbilical cyst occurs when the midportion of the duct remains patent and each end obliterates. (d) A persistent fibrous cord occurs when the duct obliterates but is not absorbed. (e, f) Meckel diverticulum results when the ileal end of the duct remains patent and the umbilical end atrophies. The diverticulum remains connected to the umbilicus by a fibrous band if the obliterated duct fails to be absorbed (e).
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Figure 1e. Drawings illustrate the spectrum of anomalies resulting from incomplete atrophy of the omphalomesenteric duct. (a) Umbilicoileal fistula is a completely patent omphalomesenteric duct connecting the ileum to the anterior abdominal wall at the umbilicus. (b) Umbilical sinus results from failure of the umbilical end of the omphalomesenteric duct to close. (c) Umbilical cyst occurs when the midportion of the duct remains patent and each end obliterates. (d) A persistent fibrous cord occurs when the duct obliterates but is not absorbed. (e, f) Meckel diverticulum results when the ileal end of the duct remains patent and the umbilical end atrophies. The diverticulum remains connected to the umbilicus by a fibrous band if the obliterated duct fails to be absorbed (e).
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Figure 1f. Drawings illustrate the spectrum of anomalies resulting from incomplete atrophy of the omphalomesenteric duct. (a) Umbilicoileal fistula is a completely patent omphalomesenteric duct connecting the ileum to the anterior abdominal wall at the umbilicus. (b) Umbilical sinus results from failure of the umbilical end of the omphalomesenteric duct to close. (c) Umbilical cyst occurs when the midportion of the duct remains patent and each end obliterates. (d) A persistent fibrous cord occurs when the duct obliterates but is not absorbed. (e, f) Meckel diverticulum results when the ileal end of the duct remains patent and the umbilical end atrophies. The diverticulum remains connected to the umbilicus by a fibrous band if the obliterated duct fails to be absorbed (e).
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Partial obliteration of the omphalomesenteric duct may result in an omphalomesenteric duct sinus or cyst, a fibrous cord, or a Meckel diverticulum. An omphalomesenteric duct sinus occurs when the distal (umbilical) end fails to close and forms a sinus tract that may vary in length (Fig 1b). The ileum remains connected by a fibrous band. Clinically, mucus discharge from the umbilicus is noted during infancy. The omphalomesenteric cyst (also called vitelline cyst) develops when the midportion of the duct remains patent while each end obliterates (Fig 1c). The cyst may be located at any location along the duct. Mucus accumulates within the cyst because it is lined by intestinal mucosa (3). A fibrous cord connecting the umbilicus to the ileum results from an atrophic omphalomesenteric duct that is not completely obliterated and absorbed (Fig 1d). Congenital fibrous bands are clinically significant because they may lead to intestinal obstruction or volvulus (5).
Meckel diverticulum is the most common (98% of cases) of the omphalomesenteric duct anomalies (3,6). The diverticulum results from fibrous obliteration of the umbilical end of the omphalomesenteric duct and complete patency of the ileal end of the duct. The diverticulum is on the antimesenteric side of the ileum and may connect to the umbilicus by a fibrous band if the fibrous portion of the duct fails to be completely obliterated and absorbed (Fig 1e, 1f). The diverticulum is usually found within 100 cm of the ileocecal valve on the antimesenteric border of the ileum. The arterial blood supply and venous drainage of a Meckel diverticulum are through remnants of the embryologic omphalomesenteric (vitellointestinal) vessels that lie within a separate fold of the small intestinal mesentery supporting the diverticulum or along the surface of the diverticulum (7).
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Clinical Features
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Meckel diverticulum occurs in 2%–3% of the population (1). There is no known gender predilection for the formation of Meckel diverticulum. Those found incidentally at autopsy and surgery are found with equal frequency in both sexes (8). However, symptomatic Meckel diverticulum is more common in men than women. The male-to-female ratio of patients with symptoms is reported to be higher in the Japanese population (male:female, 2.4–2.8:1) compared with the United States and European populations (male:female, 1.6–1.8:1) (9–11). Meckel diverticulum has no associations with other major congenital malformations. There is a higher prevalence (5%–8%) of Meckel diverticulum in patients with Crohn disease compared with the general population (12,13). The explanation for and clinical significance of this association are not clear. It has been hypothesized that infectious or inflammatory agents may be present within the diverticulum that increase gastrointestinal permeability or that the diverticulum provides a site of mechanical or motility disturbance in the distal small intestine that promotes ischemia and a predisposition for the development of Crohn disease (12).
In the majority of patients, Meckel diverticulum is asymptomatic. Many Meckel diverticula are discovered incidentally during a radiologic evaluation or surgical procedure performed for other reasons or they are found at autopsy. It is generally stated throughout the medical literature that 25% of Meckel diverticula become symptomatic. However, in a retrospective study of 202 patients, Soltero and Bill (14) calculated that the lifetime risk of developing complications from a Meckel diverticulum is 4% up to the age of 20 years, 2% up to the age of 40 years, and zero in the elderly population.
Clinical symptoms from complications of Meckel diverticulum occur more commonly in children than adults. Sixty percent of Meckel diverticula become symptomatic before patients reach 10 years of age. Hemorrhage is the most frequent complication in the pediatric population, and it is almost always associated with peptic ulceration from heterotopic gastric mucosa located within the diverticulum (15). The mucosal ulcer may be located in the diverticulum or in the adjacent ileum. The bleeding is usually painless. It can be massive and dramatic, manifesting as bright red blood in the stool, or slow and occult, manifesting as guaiac-positive stools or anemia. Profuse bleeding is usually self-limited because of physiologic contraction of the splanchnic vessels in response to hypovolemia (8). The stool of a patient with an actively bleeding Meckel diverticulum is classically bright red and has a texture that is comparable to "current jelly." The phrase "brick red" is also used to describe the color of stool in a patient with a bleeding Meckel diverticulum.
Intestinal obstruction is the second most common complication. It is usually seen in older children and adults. The reported prevalence of complications of Meckel diverticula in adult patients ranges from 26% to 53% (16). Clinical symptoms include bilious vomiting, abdominal distension, periumbilical pain, and constipation. There are many mechanisms for small intestinal obstruction from a Meckel diverticulum. These mechanisms include intussusception; volvulus or internal hernia from persistent attachment of the diverticulum to the umbilicus by the obliterated omphalomesenteric duct, mesodiverticular band, or adhesion; luminal obstruction from an inverted diverticulum, diverticulitis, or foreign body impacted in the diverticulum; inclusion of the diverticulum into a hernia; neoplastic obstruction; or rarely, the inclusion of a Meckel diverticulum in a true knot that forms between the ileum and sigmoid.
Acute Meckel diverticulitis usually manifests as abdominal pain, fever, and vomiting. The clinical presentation may be indistinguishable from that of acute appendicitis. If the diverticulum is located at a distance from the ileocecal valve, the location of maximal abdominal tenderness may be in the left lower quadrant or midabdomen. The pathogenesis of Meckel diverticulitis is related to obstruction or narrowing of the mouth of the diverticulum by an enterolith, fecolith, parasite, foreign body, neoplasm, or inflammation and fibrosis from peptic ulceration.
Enteroliths are considered rare complications of Meckel diverticulum, but they were found in 10% of the cases reported from our institution (17). Patients with enteroliths had a median age of 45 years and presented with chronic, intermittent abdominal pain or gastrointestinal bleeding (17).
Meckel diverticulum entrapped in a hernia has become known as Littre hernia. Although the original description by Alexis Littre in 1700 reported a small intestinal diverticulum incarcerated in a femoral hernia (18), the term is now used to describe the presence of a Meckel diverticulum in a hernia in any location. Fifty percent of Meckel diverticula in hernias occur in the inguinal region (Fig 2); 20%, in a femoral location; 20%, in an umbilical location; and the remanding 10% in other locations (19). The clinical presentation of patients with Littre hernias is indolent. The symptoms of abdominal distension, pain, fever, and vomiting typically evolve slower than the symptoms in patients who have small intestine entrapped in a hernia (19).
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Pathologic Features
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Gross Features
Meckel diverticulum is always on the antimesenteric border of the distal ileum. The location of Meckel diverticulum in the ileum varies from patient to patient, but it is usually found within 100 cm of the ileocecal valve. It is usually closer to the ileocecal valve in infants (30–90 cm) compared with adults (60–100 cm) (5). Meckel diverticulum may be connected to the umbilicus by a fibrous band or to adjacent segments of intestine or mesentery by congenital fibrous bands (mesodiverticular bands) or adhesions (20). In many cases, a separate fold of the small intestinal mesentery supports the diverticulum (Fig 1f). There is substantial variability in the size and shape of Meckel diverticula from patient to patient. The length and width of the diverticulum are variable as well (Fig 3). The length of a Meckel diverticulum may measure up to 15 cm (20). Giant Meckel diverticula are considered to be those more than 5–6 cm in diameter (21).
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Figure 3a. (a) Intraoperative photograph of a 19-year-old man who presented with gastrointestinal bleeding shows the serosal surface of a 4.0 x 2.5-cm Meckel diverticulum (M) located on the antimesenteric side of the ileum. (b) Intraoperative photograph of the serosal surface of the distal ileum in a 44-year-old woman with guaiac-positive stools and anemia shows a 1-cm diverticulum on the antimesenteric border.
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Figure 3b. (a) Intraoperative photograph of a 19-year-old man who presented with gastrointestinal bleeding shows the serosal surface of a 4.0 x 2.5-cm Meckel diverticulum (M) located on the antimesenteric side of the ileum. (b) Intraoperative photograph of the serosal surface of the distal ileum in a 44-year-old woman with guaiac-positive stools and anemia shows a 1-cm diverticulum on the antimesenteric border.
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Histologic Features
Meckel diverticulum is a true diverticulum that is composed of all layers of the ileal wall. Normal small intestinal epithelium lines the diverticulum (Fig 4). Heterotopic tissue is found in approximately 50% of resected Meckel diverticula. Gastric heterotopia is most common, reported in 23%–50% of cases (22,23). The gastric mucosa may be fundic, body, antral, or pyloric in type. Fundic and body mucosa contain oxyntic glands with parietal, chief, and mucous neck cells (Fig 5). Heterotopic pancreatic tissue is found in 5%–16% of cases (24). Pancreatic acini, ducts, and islets may occur alone or in combination with one another (Fig 6). The heterotopic pancreatic tissue may be located in the distal tip of the diverticulum and serve as a lead point for intussusception. Rarely, other heterotopic tissue may occur, such as that from duodenal Brunner glands or colonic or biliary epithelium (20).
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Figure 4a. Meckel diverticulum. (a) Photomicrograph (original magnification, x16; hematoxylin-eosin [H-E] stain) shows the diverticulum composed of all layers of the intestinal wall. Normal small intestinal mucosa and a focus of gastric mucosa (arrow) line the diverticulum. (b) Photomicrograph (original magnification, x48; H-E stain) shows normal small intestinal mucosa with goblet cells along the luminal surface (arrow).
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Figure 4b. Meckel diverticulum. (a) Photomicrograph (original magnification, x16; hematoxylin-eosin [H-E] stain) shows the diverticulum composed of all layers of the intestinal wall. Normal small intestinal mucosa and a focus of gastric mucosa (arrow) line the diverticulum. (b) Photomicrograph (original magnification, x48; H-E stain) shows normal small intestinal mucosa with goblet cells along the luminal surface (arrow).
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Figure 5a. Heterotopic gastric mucosa in Meckel diverticulum. (a, b) Photomicrographs (original magnification, x40; H-E stain) show gastric fundic mucosa surfaced by foveolar cells (straight arrow). Oxyntic glands (curved arrow in b) contain eosinophilic parietal cells adjacent to basophilic chief cells. (c) Photomicrograph (original magnification, x40; H-E stain) shows small intestinal epithelium with goblet cells (*) adjacent to typical gastric epithelium (arrow). (d) Photomicrograph (original magnification, x16; H-E stain) shows erosions in the mucosa (arrowhead) with underlying heterotopic gastric antral glands (arrow).
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Figure 5b. Heterotopic gastric mucosa in Meckel diverticulum. (a, b) Photomicrographs (original magnification, x40; H-E stain) show gastric fundic mucosa surfaced by foveolar cells (straight arrow). Oxyntic glands (curved arrow in b) contain eosinophilic parietal cells adjacent to basophilic chief cells. (c) Photomicrograph (original magnification, x40; H-E stain) shows small intestinal epithelium with goblet cells (*) adjacent to typical gastric epithelium (arrow). (d) Photomicrograph (original magnification, x16; H-E stain) shows erosions in the mucosa (arrowhead) with underlying heterotopic gastric antral glands (arrow).
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Figure 5c. Heterotopic gastric mucosa in Meckel diverticulum. (a, b) Photomicrographs (original magnification, x40; H-E stain) show gastric fundic mucosa surfaced by foveolar cells (straight arrow). Oxyntic glands (curved arrow in b) contain eosinophilic parietal cells adjacent to basophilic chief cells. (c) Photomicrograph (original magnification, x40; H-E stain) shows small intestinal epithelium with goblet cells (*) adjacent to typical gastric epithelium (arrow). (d) Photomicrograph (original magnification, x16; H-E stain) shows erosions in the mucosa (arrowhead) with underlying heterotopic gastric antral glands (arrow).
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Figure 5d. Heterotopic gastric mucosa in Meckel diverticulum. (a, b) Photomicrographs (original magnification, x40; H-E stain) show gastric fundic mucosa surfaced by foveolar cells (straight arrow). Oxyntic glands (curved arrow in b) contain eosinophilic parietal cells adjacent to basophilic chief cells. (c) Photomicrograph (original magnification, x40; H-E stain) shows small intestinal epithelium with goblet cells (*) adjacent to typical gastric epithelium (arrow). (d) Photomicrograph (original magnification, x16; H-E stain) shows erosions in the mucosa (arrowhead) with underlying heterotopic gastric antral glands (arrow).
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Figure 6a. Heterotopic pancreatic tissue in Meckel diverticulum. (a) Photomicrograph (original magnification, x10; H-E stain) shows a round focus of heterotopic pancreatic tissue (arrow) and multiple heterotopic gastric glands (arrowheads). Extensive ulceration is seen. (b) Photomicrograph (original magnification, x160; H-E stain) shows pancreatic acini. (c) Photomicrograph (original magnification, x80; H-E stain) shows pancreatic acinar cells and islets (arrow). (d) Photomicrograph (original magnification, x64; H-E stain) shows pancreatic ducts (*) surrounded by smooth muscle.
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Figure 6b. Heterotopic pancreatic tissue in Meckel diverticulum. (a) Photomicrograph (original magnification, x10; H-E stain) shows a round focus of heterotopic pancreatic tissue (arrow) and multiple heterotopic gastric glands (arrowheads). Extensive ulceration is seen. (b) Photomicrograph (original magnification, x160; H-E stain) shows pancreatic acini. (c) Photomicrograph (original magnification, x80; H-E stain) shows pancreatic acinar cells and islets (arrow). (d) Photomicrograph (original magnification, x64; H-E stain) shows pancreatic ducts (*) surrounded by smooth muscle.
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Figure 6c. Heterotopic pancreatic tissue in Meckel diverticulum. (a) Photomicrograph (original magnification, x10; H-E stain) shows a round focus of heterotopic pancreatic tissue (arrow) and multiple heterotopic gastric glands (arrowheads). Extensive ulceration is seen. (b) Photomicrograph (original magnification, x160; H-E stain) shows pancreatic acini. (c) Photomicrograph (original magnification, x80; H-E stain) shows pancreatic acinar cells and islets (arrow). (d) Photomicrograph (original magnification, x64; H-E stain) shows pancreatic ducts (*) surrounded by smooth muscle.
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Figure 6d. Heterotopic pancreatic tissue in Meckel diverticulum. (a) Photomicrograph (original magnification, x10; H-E stain) shows a round focus of heterotopic pancreatic tissue (arrow) and multiple heterotopic gastric glands (arrowheads). Extensive ulceration is seen. (b) Photomicrograph (original magnification, x160; H-E stain) shows pancreatic acini. (c) Photomicrograph (original magnification, x80; H-E stain) shows pancreatic acinar cells and islets (arrow). (d) Photomicrograph (original magnification, x64; H-E stain) shows pancreatic ducts (*) surrounded by smooth muscle.
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It has been long held that the pathogenesis of inflammation, ulceration, perforation, and hemorrhage in a Meckel diverticulum was secondary to peptic ulceration from heterotopic gastric mucosa. Several authors have explored the possibility that Helicobacter pylori may play a role in the pathogenesis of complications within Meckel diverticula (22,25,26). H pylori has been reported to colonize heterotopic mucosa within Meckel diverticulum, but there has been no convincing evidence published to date that H pylori plays a role in the pathogenesis of complications of Meckel diverticulum (27).
Histologic features of inflammation that may be seen in a Meckel diverticulum include the presence of neutrophils in the lamina propria or epithelium and expansion of the lamina propria by chronic inflammatory cells. Attenuation of the superficial epithelium, villous atrophy, and mucosal erosion may also be present (Fig 7). With severe inflammation, ulceration (Fig 8), mucosal hemorrhage, and edema may occur. Lymphoid aggregates and hyperplasia may be present. With more substantial inflammation and subsequent bacterial superinfection, abscesses form within the wall of the Meckel diverticulum and perforation may occur.
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Figure 7a. Meckel diverticulitis. (a) Photomicrograph (original magnification, x16; H-E stain) shows submucosal edema and hemorrhage (S). There is a microabscess within the muscularis propria (arrow), as well as an inflammatory infiltrate in the subserosal fat (*). (b) Photomicrograph (original magnification, x40; H-E stain) shows regenerative epithelium (arrow) over a healing ulcer with granulation tissue. There is abundant fibropurulent exudate in the lumen (*).
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Figure 7b. Meckel diverticulitis. (a) Photomicrograph (original magnification, x16; H-E stain) shows submucosal edema and hemorrhage (S). There is a microabscess within the muscularis propria (arrow), as well as an inflammatory infiltrate in the subserosal fat (*). (b) Photomicrograph (original magnification, x40; H-E stain) shows regenerative epithelium (arrow) over a healing ulcer with granulation tissue. There is abundant fibropurulent exudate in the lumen (*).
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Figure 8a. Ulceration in Meckel diverticulum. (a) Photomicrograph (original magnification, x16; H-E stain) shows marked ulceration of the mucosal surface (arrow). An inflammatory infiltrate and hemorrhage are present. There is a focus of heterotopic pancreatic ducts (*). (b) Photomicrograph (original magnification, x16; H-E stain) shows peptic ulceration in an area of oxyntic gastric epithelium.
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Figure 8b. Ulceration in Meckel diverticulum. (a) Photomicrograph (original magnification, x16; H-E stain) shows marked ulceration of the mucosal surface (arrow). An inflammatory infiltrate and hemorrhage are present. There is a focus of heterotopic pancreatic ducts (*). (b) Photomicrograph (original magnification, x16; H-E stain) shows peptic ulceration in an area of oxyntic gastric epithelium.
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Radiologic Features
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The radiologic diagnosis of Meckel diverticulum is most relevant for those patients presenting with clinical signs and symptoms of its complications. The imaging evaluation of patients should be tailored to their age and clinical presentation and is discussed in the following sections of this article. Although conventional barium studies (small bowel follow-through study, enteroclysis, or retrograde ileal opacification by means of barium enema) have been largely replaced by other imaging modalities for evaluation of patients with acute symptoms, they continue to have a role in the examination of patients who have persistent symptoms despite negative cross-sectional imaging findings. In selected cases, barium evaluation of the small intestine may be complementary to cross-sectional imaging studies when the diagnosis of Meckel diverticulum is in question.
It has been shown that conventional barium studies can help diagnose Meckel diverticulum accurately when meticulous technique is used (5,28,29). Meckel diverticulum is identified as a saccular, blind-ending structure located on the antimesenteric border of the ileum. The antimesenteric location can be confirmed from the position of the diverticulum, which faces away from the axis of the root of the small intestinal mesentery (Fig 9). Meckel diverticulum is usually found in the right lower quadrant and pelvic region, but it may have a periumbilical location (Fig 10). Periumbilical or midabdominal locations may be secondary to adhesions or congenital bands that fix the diverticulum to the umbilicus or adjacent intestinal segments.
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Figure 9a. Barium examination of the small intestine demonstrating Meckel diverticulum. (a) Image from a small bowel follow-through study in a 10-year-old girl with intermittent bloody stools and anemia shows a wide-mouthed Meckel diverticulum (arrow) on the antimesenteric border of the ileum. The tip of the diverticulum points away from the root of the small bowel mesentery. (b) Image from a small bowel follow-through study in an 11-year-old girl with abdominal pain and anemia shows an elongated Meckel diverticulum extending from the antimesenteric border of the distal ileum. The neck of the diverticulum is narrow (arrow). (Fig 9b courtesy of William M. Thompson, MD, Duke University, Durham, NC.)
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Figure 9b. Barium examination of the small intestine demonstrating Meckel diverticulum. (a) Image from a small bowel follow-through study in a 10-year-old girl with intermittent bloody stools and anemia shows a wide-mouthed Meckel diverticulum (arrow) on the antimesenteric border of the ileum. The tip of the diverticulum points away from the root of the small bowel mesentery. (b) Image from a small bowel follow-through study in an 11-year-old girl with abdominal pain and anemia shows an elongated Meckel diverticulum extending from the antimesenteric border of the distal ileum. The neck of the diverticulum is narrow (arrow). (Fig 9b courtesy of William M. Thompson, MD, Duke University, Durham, NC.)
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Figure 10a. Enteroliths in a Meckel diverticulum in a 40-year-old man with chronic, intermittent abdominal pain. (a) Supine abdominal radiograph demonstrates multiple stones with peripheral calcification (arrow) in the right upper quadrant. (b) Image from a small bowel follow-through study shows a Meckel diverticulum in the right midabdomen (arrow). The dense collection of barium obscures the stones.
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Figure 10b. Enteroliths in a Meckel diverticulum in a 40-year-old man with chronic, intermittent abdominal pain. (a) Supine abdominal radiograph demonstrates multiple stones with peripheral calcification (arrow) in the right upper quadrant. (b) Image from a small bowel follow-through study shows a Meckel diverticulum in the right midabdomen (arrow). The dense collection of barium obscures the stones.
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The junction of the diverticulum with the ileum may show a mucosal triangular plateau or triradiate fold pattern (Fig 11), which represents the site of omphalomesenteric duct attachment to the ileum (29). Filling defects within the diverticulum may represent enteroliths, fecoliths, or foreign bodies. Mucosal nodularity or masses within the diverticulum are occasionally encountered, and such findings represent nodular foci of heterotopic tissue, inflammation, or more rarely, neoplasia.
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Figure 11. Image from a barium study of the small intestine in a 35-year-old woman with abdominal pain shows a Meckel diverticulum. There is a triradiate fold pattern at the junction of the diverticulum with the ileum (arrow). (Courtesy of William M. Thompson, MD, Duke University, Durham, NC.)
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The diagnosis of Meckel diverticulum is virtually pathognomonic when it is correctly identified as a saccular, blind-ending pouch on the antimesenteric border of the ileum with a triradiate fold pattern converging with the ileum. There are several entities that may resemble Meckel diverticulum on barium studies and that should be considered in the differential diagnosis. These entities include acquired solitary diverticula of the small intestine; communicating enteric duplications; pseudosacculations, which are seen in motility disorders and Crohn disease; and cavitating malignancies of the small intestine, such as lymphoma and gastrointestinal stromal tumors. Cavitating malignancies should be readily differentiated from Meckel diverticulum because they usually have a component of mural thickening and they exhibit mass effect on the affected and adjacent segments of intestine.
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Imaging of Complications of Meckel Diverticulum
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Hemorrhage
Hemorrhage is the most frequent complication of Meckel diverticulum in the pediatric population. Technetium-99m pertechnetate scintigraphy is the modality of choice for evaluating pediatric patients with gastrointestinal hemorrhage and a suspected Meckel diverticulum. The mucus cells in the gastric epithelium accumulate and secrete the pertechnetate anion. After intravenous injection of Tc-99m pertechnetate, a Meckel diverticulum containing gastric mucosa will manifest as a small rounded area of increased activity in the right lower quadrant.
A Meckel diverticulum usually appears within 30 minutes of the injection, but its visualization may take up to an hour if there are small amounts of heterotopic gastric mucosa (30). Normal activity will simultaneously appear in the stomach. Occasionally, the activity of a Meckel diverticulum will be present elsewhere in the abdomen or will change positions during the course of the study (Fig 12a). Intestinal activity may appear simultaneously with the gastric and heterotopic gastric activity or later in the course of the scan (Fig 12b). Care should be taken in interpreting these studies because the presence of intestinal activity may mask the activity of heterotopic gastric mucosa in a Meckel diverticulum (31). Single photon emission computed tomography (SPECT) has been reported to demonstrate a positive Meckel diverticulum when results from conventional planar imaging are negative (32). Improved resolution provided by SPECT makes it a useful adjunct when the clinical suspicion for a bleeding Meckel diverticulum is high and findings from planar Tc-99m pertechnetate imaging are negative.
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Figure 12a. Meckel diverticulum diagnosed with Tc-99m pertechnetate scintigraphy. (a) Tc-99m pertechnetate scans of a 17-year-old boy with painless rectal bleeding show a small focus of uptake in the right lower quadrant within minutes of radiopharmaceutical injection. The activity changes shape and position during the study (arrows), which is indicative of active hemorrhage and extravasation of radioactivity into the intestinal lumen. (b) Tc-99m pertechnetate scans of a 4-year-old boy who had multiple episodes of bright red bleeding from the rectum show a persistent focus of uptake in the right lower quadrant, a finding consistent with a Meckel diverticulum. There is delayed appearance of proximal small intestinal activity (arrow), most likely secondary to transit of activity from the stomach.
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Figure 12b. Meckel diverticulum diagnosed with Tc-99m pertechnetate scintigraphy. (a) Tc-99m pertechnetate scans of a 17-year-old boy with painless rectal bleeding show a small focus of uptake in the right lower quadrant within minutes of radiopharmaceutical injection. The activity changes shape and position during the study (arrows), which is indicative of active hemorrhage and extravasation of radioactivity into the intestinal lumen. (b) Tc-99m pertechnetate scans of a 4-year-old boy who had multiple episodes of bright red bleeding from the rectum show a persistent focus of uptake in the right lower quadrant, a finding consistent with a Meckel diverticulum. There is delayed appearance of proximal small intestinal activity (arrow), most likely secondary to transit of activity from the stomach.
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In the pediatric population, the sensitivity of Tc-99m pertechnetate scintigraphy is 85%; specificity, 95%; and accuracy, 90% (33,34). Tc-99m pertechnetate scintigraphy is less sensitive (63%), specific (2%), and accurate (46%) in the adult population because the prevalence of heterotopic gastric mucosa declines with age in symptomatic Meckel diverticula, and other abdominal disorders that cause gastrointestinal bleeding are more frequently encountered (35). False-positive results may occur when there is a gastric or small intestinal duplication, heterotopic gastric mucosa in otherwise normal small intestine, or ulcerative or inflammatory processes that cause substantial intestinal hyperemia. Ulcerative colitis, Crohn disease, idiopathic intussusception, and small intestinal obstruction may also cause false-positive findings (30). False-negative results occur in Meckel diverticula that do not contain heterotopic gastric mucosa or when there is an inadequate number of gastric cells to concentrate the Tc-99m pertechnetate anion.
Scintigraphic studies that demonstrate active gastrointestinal hemorrhage are also useful to localize the site of hemorrhage in patients who are briskly bleeding. Tc-99m–labeled sulfur colloid or red blood cell scintigraphy is sensitive for the localization of the site of gastrointestinal hemorrhage, but neither technique is specific for Meckel diverticulum. Therefore, these studies are less useful for the specific diagnosis of Meckel diverticulum.
Angiography may be useful in the evaluation of an adult patient with occult or intermittent gastrointestinal bleeding for the localization of the site of bleeding, specific diagnosis, and therapeutic preoperative embolization. In these patients, the diagnosis of Meckel diverticulum is often unsuspected. Meckel diverticulum receives arterial blood supply from a remnant of the omphalomesenteric (vitellointestinal) artery, and demonstration of this artery is diagnostic of Meckel diverticulum. In some patients, the primary blood supply may also come from branches of the ileocolic artery (7). The vitellointestinal artery usually arises from a distal ileal branch of the superior mesenteric artery and may have a number of side branches (Fig 13) (36). A vascular blush may also be identified at the site of the Meckel diverticulum (Fig 13b). When active hemorrhage is occurring at the time of angiography, luminal extravasation of contrast material will be present (Fig 14).
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Figure 13a. Meckel diverticulum in a 22-year-old man with chronic abdominal pain and anemia. (a) Angiogram shows a vitellointestinal artery (arrow) arising from a distal ileal branch of the superior mesenteric artery. (b) Late arterial phase image shows a tubular-shaped angiographic blush (arrow) at the site of the diverticulum. (c) Photograph of the opened, resected surgical specimen shows a hemorrhagic Meckel diverticulum.
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Figure 13b. Meckel diverticulum in a 22-year-old man with chronic abdominal pain and anemia. (a) Angiogram shows a vitellointestinal artery (arrow) arising from a distal ileal branch of the superior mesenteric artery. (b) Late arterial phase image shows a tubular-shaped angiographic blush (arrow) at the site of the diverticulum. (c) Photograph of the opened, resected surgical specimen shows a hemorrhagic Meckel diverticulum.
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Figure 13c. Meckel diverticulum in a 22-year-old man with chronic abdominal pain and anemia. (a) Angiogram shows a vitellointestinal artery (arrow) arising from a distal ileal branch of the superior mesenteric artery. (b) Late arterial phase image shows a tubular-shaped angiographic blush (arrow) at the site of the diverticulum. (c) Photograph of the opened, resected surgical specimen shows a hemorrhagic Meckel diverticulum.
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Figure 14. Angiogram shows active hemorrhage from a Meckel diverticulum in a 26-year-old man with hematochezia. Selective injection of the ileocolic artery shows hemorrhage from a proximal branch (arrow). There is extravasation of contrast material into the intestinal lumen (arrowheads).
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Intestinal Obstruction
Although intestinal obstruction is the second most common complication of Meckel diverticulum, the diagnosis is rarely made preoperatively. The diagnosis can be made with certainty only if the diverticulum is visualized at the site of obstruction. However, the diagnosis can be suggested if features of the known complications of Meckel diverticulum can be identified on radiographs or cross-sectional images.
In the setting of intestinal obstruction, the most useful feature for the diagnosis of a Meckel diverticulum on abdominal radiographs is the identification of enteroliths. When present, enteroliths in Meckel diverticula are almost always visualized on abdominal radiographs (Fig 15). Most commonly, enteroliths manifest as peripheral calcification with a radiolucent center and less often have a laminated appearance (17). They are most commonly located in the right lower quadrant of the abdomen, but they may be present in the middle and upper abdomen if adhesions from inflammation or congenital bands fix and alter the location of the diverticulum.
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Figure 15a. Torsion of a Meckel diverticulum causing small intestinal obstruction in a 30-year-old man who presented with abdominal distension and vomiting. Supine (a) and upright (b) abdominal radiographs show features of a mechanical small intestinal obstruction and an oval air collection that contains multiple peripherally calcified stones (arrow) in the right lower quadrant. At surgery, these findings proved to represent torsion of a Meckel diverticulum and multiple enteroliths. (Courtesy of Charles Rohrmann, Jr, MD, University of Washington, Seattle.)
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Figure 15b. Torsion of a Meckel diverticulum causing small intestinal obstruction in a 30-year-old man who presented with abdominal distension and vomiting. Supine (a) and upright (b) abdominal radiographs show features of a mechanical small intestinal obstruction and an oval air collection that contains multiple peripherally calcified stones (arrow) in the right lower quadrant. At surgery, these findings proved to represent torsion of a Meckel diverticulum and multiple enteroliths. (Courtesy of Charles Rohrmann, Jr, MD, University of Washington, Seattle.)
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Computed tomography (CT) is an invaluable imaging modality for the evaluation of patients with intestinal obstruction. However, it is difficult to use CT to accurately identify a Meckel diverticulum as the cause of intestinal obstruction. Meckel diverticulum may produce obstruction by diverticular inversion causing luminal obstruction or leading an intussusception (Fig 16); volvulus from persistent attachment to the umbilicus, adhesions, or congenital mesodiverticular bands; diverticulitis (Figs 17, 18); foreign body impaction; inclusion of the diverticulum into a hernia; neoplasm; or formation of a true knot. True knots are rare causes of intestinal obstruction. When they occur, the small intestine becomes entrapped in a sigmoid volvulus. Meckel diverticulum may be included in the knot (37).
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Figure 16a. Intussuscepted Meckel diverticulum with infarction producing small intestinal obstruction in a 41-year-old woman with diffuse abdominal pain, nausea, and vomiting. (a) Intravenous contrast material-enhanced CT scan shows diffuse small intestinal dilatation. (b) Contrast-enhanced CT scan of the pelvis demonstrates an ileoileal intussusception, which appears as a thickened edematous segment of small bowel (arrowheads) with alternating bands of soft-tissue and fluid attenuation. There is a central focus of fat attenuation (arrow). (c) Photograph of the opened, resected surgical specimen shows an infarcted and necrotic Meckel diverticulum (arrow) that was the lead point of the intussusception.
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Abstract
LEARNING OBJECTIVES FOR TEST...
