Radiography
Findings
- Plain radiographs may demonstrate appearances typical of an intestinal obstruction.1,5,12
- If the diverticulum is distended, a gas-filled viscus seen in the right iliac fossa or the mid abdomen may provide a clue to the diagnosis.
- The presence of an enterolith may further support the diagnosis.
- When perforation is a complication, plain abdominal and upright chest radiographs may reveal features of a pneumoperitoneum.
- Although a conventional small-bowel barium meal is usually not helpful in routinely depicting Meckel diverticulum in many patients, the anomaly can be detected if careful technique is applied.1,4 Some limitations encountered by using barium series are the overlapping of small bowel loops, the inability to achieve adequate distention, and the failure to adequately depict the mucosal pattern in the distal ileum. The yield improves with meticulous technique and spot compression imaging. The diagnostic yield is also improved with enteroclysis.
- Barium enema study probably reveals most Meckel diverticula when sufficient reflux is achieved into the terminal ileum.13
- Typically, the diverticulum is depicted as a contrast-filled outpouching, 0.5 to 20 cm long, that is located on the antimesenteric border of the ileum and has a junctional-fold pattern. The site of origin of a Meckel diverticulum rests on the demonstration of its junctional-fold pattern at the site of attachment. The characteristic junctional-fold appearances are a triradiate fold pattern, in which the loops are collapsed, and a mucosal triangular plateau, in which the loops are distended.
- An inverted Meckel diverticulum without an intussusception, which occurs in 20% of patients, appears as an elongated, smoothly marginated, clublike intraluminal mass parallel to the long axis of the ileum.
- Rarely, a gastric rugal pattern, intraluminal filling defects, and mucosal irregularity are identified. These are suggestive of ectopic gastric mucosa.
Degree of Confidence
Findings 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/Negatives
The 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.
Computed Tomography
Findings
CT 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 Confidence
Sufficient experience has not been gained to suggest the degree of confidence with CT.
False Positives/Negatives
Intussusception from other causes may appear similar to intussusception associated with Meckel diverticulum on CT scans.
Ultrasonography
Findings
The 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 Confidence
Occasionally, 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/Negatives
The 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 Imaging
Findings
The 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 (99m Tc)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 Confidence
Scintigraphy 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/Negatives
False-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. Because99m Tc 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.
Angiography
Findings
In 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 Confidence
Angiography has an accuracy of 59%.
False Positives/Negatives
Bleeding 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.
More on Meckel Diverticulum |
| Overview: Meckel Diverticulum |
 Imaging: Meckel Diverticulum |
| Follow-up: Meckel Diverticulum |
| Multimedia: Meckel Diverticulum |
| References |
| « Previous Page | Next Page » |
References
Pantongrag-Brown L, Levine MS, Buetow PC, et al. Meckel''s enteroliths: clinical, radiologic, and pathologic findings. AJR Am J Roentgenol. Dec 1996;167(6):1447-50. [Medline].
Ariga M, Suga K, Matsunaga N, et al. Failure to detect a huge Meckel''s diverticulum with abundant ectopic gastric mucosa on gastric mucosal scintigraphy with Tc-99m pertechnetate. Clin Nucl Med. May 2001;26(5):470-1. [Medline].
Ford PV, Bartold SP, Fink-Bennett DM, et al. Procedure guideline for gastrointestinal bleeding and Meckel''s diverticulum scintigraphy. Society of Nuclear Medicine. J Nucl Med. Jul 1999;40(7):1226-32. [Medline].
Groebli Y, Bertin D, Morel P. Meckel''s diverticulum in adults: retrospective analysis of 119 cases and historical review. Eur J Surg. Jul 2001;167(7):518-24. [Medline].
Hol L, Kuipers EJ. Clinical challenges and images in GI. Meckel's diverticulum. Gastroenterology. Aug 2007;133(2):392, 732. [Medline].
You JS, Chung SP, Park YS, Yu JS, Park YA. A case of strangulated small bowel obstruction caused by Meckel's diverticulum in an adult. J Emerg Med. Aug 2007;33(2):133-5. [Medline].
van Es HW, Sybrandy R. Diagnosis please. Case 19: enteroliths in a Meckel diverticulum. Radiology. Feb 2000;214(2):524-6. [Medline].
Emamian SA, Shalaby-Rana E, Majd M. The spectrum of heterotopic gastric mucosa in children detected by Tc- 99m pertechnetate scintigraphy. Clin Nucl Med. Jun 2001;26(6):529-35. [Medline].
Linebarger JS, Roy ML. Focus on diagnosis: common nuclear medicine studies in pediatrics. Pediatr Rev. Nov 2007;28(11):415-7. [Medline].
Delle Chiaie L, Neuberger P. Early prenatal sonographic detection of an uncomplicated Meckel diverticulum. Ultrasound Obstet Gynecol. Oct 2007;30(5):790-1. [Medline].
Mitchell AW, Spencer J, Allison DJ, Jackson JE. Meckel''s diverticulum: angiographic findings in 16 patients. AJR Am J Roentgenol. May 1998;170(5):1329-33. [Medline].
Navarro O, Dugougeat F, Kornecki A, et al. The impact of imaging in the management of intussusception owing to pathologic lead points in children. A review of 43 cases. Pediatr Radiol. Sep 2000;30(9):594-603. [Medline].
Nolan DJ. The true yield of the small-intestinal barium study. Endoscopy. Aug 1997;29(6):447-53. [Medline].
Omar AM, Al-Saee''d TA, Elgazzar A. Scintigraphic pattern of intestinal duplication on a Meckel''s diverticulum scan. Clin Nucl Med. Oct 1998;23(10):708-9. [Medline].
Swaniker F, Soldes O, Hirschl RB. The utility of technetium 99m pertechnetate scintigraphy in the evaluation of patients with Meckel''s diverticulum. J Pediatr Surg. May 1999;34(5):760-4; discussion 765. [Medline].
Okazaki M, Higashihara H, Yamasaki S, et al. Arterial embolization to control life-threatening hemorrhage from a Meckel''s diverticulum. AJR Am J Roentgenol. Jun 1990;154(6):1257-8. [Medline].
Further Reading
Keywords
Meckel's diverticulum, Meckel diverticula, diverticulum of the ileum, intestinal obstruction, intestinal hemorrhage, hernia of Littre
