You are in: eMedicine Specialties > Radiology > PEDIATRICS Meckel DiverticulumArticle Last Updated: May 6, 2008AUTHOR AND EDITOR INFORMATIONSection 1 of 11
  Author: Ali Nawaz Khan, MBBS, FRCS, FRCP, FRCR, LRCP, Chairman of Medical Imaging, Professor of Radiology, NGHA, King Fahad National Guard Hospital, King Abdulaziz Medical City, Riyadh, Saudi Arabia Ali Nawaz Khan is a member of the following medical societies: American Institute of Ultrasound in Medicine, Radiological Society of North America, Royal College of Physicians, Royal College of Physicians and Surgeons of the United States, Royal College of Radiologists, and Royal College of Surgeons of England Coauthor(s): Muthusamy Chandramohan, MBBS, DMRD, FRCR, Consultant Radiologist, Bradford Teaching Hospitals, UK; Sumaira MacDonald, MBChB, PhD, MRCP, FRCR, Lecturer, Sheffield University Medical School; Endovascular Fellow, Sheffield Vascular Institute Editors: Robert J Starshak, MD, Medical Director, Assistant Clinical Professor, Department of Radiology, Medical College of Wisconsin, Falls Medical Group; Bernard D Coombs, MB, ChB, PhD, Consulting Staff, Department of Specialist Rehabilitation Services, Hutt Valley District Health Board, New Zealand; David A Stringer, BSc, MBBS, FRCR, FRCPC, Professor, National University of Singapore; Head, Diagnostic Imaging, KK Women's and Children's Hospital, Singapore; Robert M Krasny, MD, Consulting Staff, Department of Radiology, The Angeles Clinic and Research Institute; John Karani, MBBS, FRCR, Consulting Staff, Department of Radiology, King's College Hospital, London Author and Editor Disclosure Synonyms and related keywords: Meckel's diverticulum, Meckel diverticula, diverticulum of the ileum, intestinal obstruction, intestinal hemorrhage, hernia of Littre INTRODUCTIONSection 2 of 11
  BackgroundMeckel diverticulum represents a true diverticulum of the ileum containing all 3 layers of the bowel wall. Meckel diverticulum develops if the omphalomesenteric or vitelline duct, which connects the primitive midgut with the yolk sac, fails to obliterate, which normally occurs at 7-8 weeks of gestation. Heterotopic tissue, including gastric mucosa and pancreatic tissue, is present in 50% of patients. Symptoms resulting from a Meckel diverticulum occur because of complications and are more frequent in children than in adults and include hemorrhage and intestinal obstruction. Hemorrhage is usually due to erosion of adjacent ileal mucosa by acid produced by ectopic gastric mucosa. Intestinal obstruction is most often due to volvulus about the Meckel diverticulum or intussusception with the diverticulum as the lead point.1 Meckel diverticulum is notoriously difficult to diagnose at both clinical and imaging examination because the symptoms and imaging features are nonspecific.1, 2, 3, 4, 5 PathophysiologyEctopic gastric or pancreatic mucosa is found in 50% of patients with Meckel diverticula. Rarely, colonic or hepatobiliary tissue is found. Symptoms may develop because of ulceration within the gastric or adjacent ileal mucosa and gastrointestinal bleeding. Intestinal obstruction, perforation, and inflammation are further complications (see Mortality/Morbidity, below).5, 6 Single or multiple enteroliths may develop within the lumen of the diverticulum in as many as 10% of patients. Most enteroliths show a peripheral calcification. Obstruction of the lumen by an enterolith may lead to diverticulitis. Extrusion of an enterolith into the lumen of the small bowel may cause intestinal obstruction similar to a gallstone ileus. Herniation of a Meckel diverticulum into the inguinal canal is called a hernia of Littre.1, 7 FrequencyUnited StatesMeckel diverticulum is found in 2-3% of individuals at autopsy, and it is the most common congenital anomaly of the gastrointestinal tract. InternationalWorldwide, the frequency of Meckel diverticulum is the same as that in the United States. Mortality/MorbidityComplications resulting from a Meckel diverticulum occur in 20% of patients. Most patients present with unexplained lower gastrointestinal bleeding. In most of these patients (95%), ectopic gastric mucosa within the diverticulum causes the bleeding.3 The second most common complication is intestinal obstruction, which results either from intussusception of the diverticulum into the lumen of the small bowel (inverted diverticulum) or from a volvulus. A volvulus occurs around a fibrous band attaching the omphalomesenteric diverticulum to the umbilicus. The diverticulum may become inflamed as a result of obstruction by an enterolith. The diverticulum may become herniated into the inguinal canal and cause intestinal obstruction.1, 7 Rarely, benign and malignant tumors may both occur within a Meckel diverticulum and include polyps, carcinoid tumors, adenocarcinoma, and sarcoma. The incidence of tumors reported with Meckel diverticulum is 0.5-3.2%. Occasionally, an ulcer in a patient with Meckel diverticulum becomes perforated, leading to peritonitis. The highest morbidity and mortality rates occur with volvulus. RaceNo race predilection exists. SexThe male-to-female ratio is 3:1. AgeMost patients with symptoms of Meckel diverticula present when they are younger than 10 years.8, 9 AnatomyThe primitive endodermal tube of the gut is divided into the foregut, which is supplied by the celiac axis; the midgut, which is supplied by the superior mesenteric artery; and the hindgut, which is supplied by the inferior mesenteric artery. Early in development, the rapid proliferation of the gut wall obliterates the lumen, which is followed by recanalization. The midgut enlarges rapidly during the first 5 weeks of gestation and becomes too large for the abdominal cavity; subsequently, it is herniated into the umbilical cord. The apex of the herniated midgut is continuous with the vitellointestinal duct and the yolk sac, which, even at this early stage of development, is reduced to a fibrous strand. The axis of the herniated midgut is formed by the superior mesenteric artery, which subdivides the midgut into a cephalic and caudal limb. The cephalic limb eventually forms most of the upper small bowel, while the caudal limb forms the terminal 60 cm or so of the small bowel, cecum, and colon as far as the junction of the proximal two thirds and distal one third of the transverse colon. At approximately the 10th week of gestation, the midgut begins its return into the abdominal cavity. This return occurs by a highly complex developmental process, and as a result, numerous anomalies of the bowel may ensue, which include bowel atresias and stenoses, abnormalities of the vitellointestinal duct, failure of cecal descent, malrotation, malfixation, reversed bowel rotation, and exomphalos.10 Meckel diverticulum is a remnant of the embryonic vitellointestinal duct, which is a communication between the primitive midgut and the yolk sac; thus, a Meckel diverticulum is always on the antimesenteric border. Occasionally, the diverticulum ends in a fibrous solid strand. The vitellointestinal duct may persist as a fistula or fibrous band connecting the small bowel to the umbilicus or as a cyst within a fibrous band passing from the antimesenteric border of the small bowel to the umbilicus (see Images 1-4). Clinical DetailsPatients may present with acute or chronic gastrointestinal bleeding. Some patients are evaluated primarily for anemia. Vague pain in the lower abdomen is not unusual and may be present for several years. Patients may present with an acute abdomen resulting from acute diverticulitis, intestinal obstruction, or perforation; however, most patients with Meckel diverticula are asymptomatic, and the diverticulum is found incidentally on imaging, surgery, or autopsy. Preferred ExaminationPlain radiography, barium studies, angiography, computed tomography (CT), ultrasonography, and scintigraphy all play complementary roles in the diagnosis of the complications of Meckel diverticulum. The diagnosis is notoriously difficult and remains a continuing challenge for the radiologist.1, 4, 5, 8, 9, 10, 11, 12, 13, 14, 15 Limitations of TechniquesIn all imaging modalities, findings of Meckel diverticulum are nonspecific. Most Meckel diverticula are diagnosed during surgery or autopsy, with imaging playing a secondary role. The most sensitive technique is scintigraphy, and various modifications to imaging techniques have been devised to improve sensitivity. Ultrasonography and CT are improving and can help in making an anatomic diagnosis. DIFFERENTIALSSection 3 of 11
Abdominal Aortic Aneurysm, Diagnosis Embolization, Hemorrhage Embolization, Vascular Lesions Gastrointestinal Bleeding, Lower Gastrointestinal Stromal Tumors - Leiomyoma/Leiomyosarcoma Intussusception, Child Small-Bowel Obstruction RADIOGRAPHSection 4 of 11
Findings
Degree of ConfidenceFindings on plain abdominal radiographs are nonspecific. A conventional small-bowel barium examination has a low yield because the diverticula fill transiently and surrounding loops of small bowel tend to overlap and obscure the diverticula.13 Enteroclysis can detect as many as 50% of Meckel diverticula. Retrograde small-bowel examination probably helps in detecting most Meckel diverticula because of the distal location. False Positives/NegativesThe neck of the diverticulum may become occluded by inflammation, which makes it difficult for the diverticulum to fill with barium; thus, a false-negative diagnosis may occur. Similarly, if the neck of the diverticulum is wide at the point where peristaltic activity tends to keep the diverticulum empty or partially filled, the result is a false-negative finding. Demonstration of Meckel diverticulum does not necessarily mean that the diverticulum is the cause of symptoms. A barium examination involves simply filling the diverticulum with barium. In an actively bleeding patient, barium examination does not show whether the bleeding originates in the diverticulum. Rarely, a false-positive diagnosis may occur with acquired small-bowel diverticula (occurs in patients >40 y) and bowel duplications. CT SCANSection 5 of 11
FindingsCT rarely is used as a primary imaging modality in patients in whom Meckel diverticulum is suspected. Most diagnoses made by using CT scans are incidental. An inverted Meckel diverticulum associated with an intussusception may be revealed as an intraluminal mass composed of a central area of fat attenuation representing the entrapped mesenteric fat of the inverted diverticulum, surrounded by a thick collar of soft-tissue attenuation.6 Degree of ConfidenceSufficient experience has not been gained to suggest the degree of confidence with CT. False Positives/NegativesIntussusception from other causes may appear similar to intussusception associated with Meckel diverticulum on CT scans. ULTRASOUNDSection 6 of 11
FindingsThe orifice of the diverticulum may become occluded. When this occurs, the wall becomes inflamed and the diverticulum is distended by fluid. Acute inflammation may mimic appendicitis. These diverticula are rarely revealed on sonograms, but they have been noted when they are distended by fluid. Sonographically, Meckel diverticulum may be identified when complications occur, such as a fluid-filled overdistended tube connected to the umbilicus. This tubular structure can be differentiated from an inflamed appendix because the former is larger and is located farther from the cecum. Two target signs of different sizes have been described in a double intussusception of the Meckel diverticulum into the ileum and the ileum into the colon. Degree of ConfidenceOccasionally, intussusception secondary to Meckel diverticulum has been diagnosed by using sonograms. However, the sensitivity and specificity of ultrasonographic examination generally is low. Ultrasonography is usually the first investigation used in young patients presenting with abdominal pain because it is noninvasive, but its role in evaluating gastrointestinal hemorrhage is limited. False Positives/NegativesThe exact percentage of false-negative findings with diverticulitis and intussusception secondary to a Meckel diverticulum is unknown. Meckel diverticulitis and intussusception secondary to a Meckel diverticulum must be differentiated from appendicitis and other causes of intussusception. NUCLEAR MEDICINESection 7 of 11
FindingsThe mucoid cells of the gastric mucosa secrete chloride into the intestinal lumen. Excretion does not depend on the presence of the parietal cells. Technetium-99m (99mTc)pertechnetate behaves in a manner that is analogous to halide anions (eg, chloride, iodide). The mucoid surface cells of gastric mucosa, whether located normally or ectopically, actively accumulate and secrete pertechnetate into the intestine. This is the basis for detecting ectopic gastric mucosa in symptomatic Meckel diverticulum.8, 9, 14, 15 Patient preparation is important to optimize results of this technique. This includes avoiding certain procedures, such as administration of cathartics (drugs that irritate the gastrointestinal tract), contrast-enhanced studies, endoscopy, and use of enemas for 48 hours prior to the procedure. The administration of certain drugs prior to scintigraphy improves results. These drugs include pentagastrin (which stimulates radionuclide uptake), cimetidine (which inhibits release of pertechnetate from the ectopic mucosa), and glucagon (which inhibits peristalsis). Because pentagastrin also increases motility, it may be most useful when used in conjunction with glucagon. Degree of ConfidenceScintigraphy has an accuracy of 83-88%, a sensitivity of more than 85%, and a specificity of more than 95%. Sensitivity drops after adolescence. False Positives/NegativesFalse-positive results have been reported for a variety of reasons, including faulty technique, uptake at other sites of ectopic gastric mucosa (eg, in a gastrogenic cyst), and some enteric duplications. Occasionally, false-positive results are observed in a normal small bowel. Vascular anomalies are a further source of false-positive findings, such as aneurysms, arteriovenous malformations, hemangiomas, and hypervascular tumors. Because 99mTc pertechnetate is excreted by the kidneys, horseshoe kidneys, caliceal diverticulum, and urinary tract obstruction resulting from a variety of causes may cause false-positive scans. False-positive scans also may occur with a variety of bowel ulcerations, inflammations, and obstructions, including those due to duodenal ulcers, ulcerative colitis, Crohn disease, appendicitis, laxative abuse, intestinal obstruction, intussusception, and volvulus. These false-positive results are thought to be due to hyperemia caused by these conditions. Careful attention to the timing of appearance of abnormal accumulations of pertechnetate can aid in distinguishing the false-positive causes from those due to ectopic gastric mucosa. The accumulations of pertechnetate due to hyperemia appear early in the study and tend to fade over time. The accumulations in ectopic gastric mucosa appear at, or nearly simultaneous with, the stomach and increase in intensity in parallel with the stomach. Lateral and oblique views are often helpful in differentiating the anterior location of a diverticulum from the posterior location of urinary activity. False-negative scans may occur if the gastric mucosa mass within the diverticulum is insufficient or if intraluminal scintigraphic activity is diluted as a result of brisk hemorrhage or bowel hypersecretion. The quality of images is poor in patients who have received perchlorate or atropine. ANGIOGRAPHYSection 8 of 11
FindingsIn patients presenting with acute gastrointestinal tract bleeding from a Meckel diverticulum, superior mesenteric angiograms may demonstrate not only the site of bleeding by focal contrast agent extravasation but also the cause of bleeding. Demonstration of the vitelline artery, which is an anomalous end branch of the superior mesenteric artery, is pathognomonic. The vitelline artery originates as an ileal branch of the superior mesenteric artery; this vessel is nonbranching and directed toward the right lower quadrant of the abdomen. This artery supplies the diverticulum via a network of tortuous and irregular small vessels likened to a basket-weave pattern. Superselective technique and the use of epinephrine are recommended to cause selective constriction of the normal splanchnic circulation for optimal depiction of the site of the lesion.11 Degree of ConfidenceAngiography has an accuracy of 59%. False Positives/NegativesBleeding at a rate of 2-3 mL/min is required in adults for angiographic detection; higher rates of hemorrhage may be required in children for angiographic detection. Rarely, a Meckel diverticulum is supplied by branches arising from the ileocolic artery, which makes it more difficult to differentiate the causes of bleeding related to the cecum and ascending colon. INTERVENTIONSection 9 of 11
When diagnostic angiography images depict severe gastrointestinal tract bleeding, superselective embolization should be considered so that surgery can be performed under stable conditions.3, 11, 16 Medical/Legal Pitfalls
See also the Medscape Resource Center Medical Malpractice and Legal Issues. MULTIMEDIASection 10 of 11
REFERENCESSection 11 of 11
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