Imaging Manifestations of Meckel s Diverticulum

Imaging of Meckel s Diverticulum bdominal Imaging Pictorial Essay Khaled M. Elsayes 1 Christine O. Menias 2 Howard J. Harvin 2 Isaac R. Francis 1 Elsayes KM, Menias CO, Harvin HJ, Francis IR Keywords: abdominal imaging, congenital malformation, diverticulum, Meckel s diverticulum DOI:10.2214/JR.06.1257 Received September 22, 2006; accepted after revision January 15, 2007. 1 Department of Radiology, University of Michigan Health Center at nn rbor, nn rbor, MI 48100-0030. ddress correspondence to K. M. Elsayes (kelsayes@med.umich.edu). 2 Mallinckrodt Institute of Radiology, Washington University, St. Louis, MO. CME This article is available for CME credit. See www.arrs.org for more information. JR 2007; 189:81 88 0361 803X/07/1891 81 merican Roentgen Ray Society Imaging Manifestations of Meckel s Diverticulum OJECTIVE. Meckel s diverticulum is the most common congenital anomaly of the gastrointestinal tract, found in 2% of the population in autopsy studies. Most patients remain asymptomatic during their lifetime. Complications of Meckel s diverticulum are reported to occur in approximately 4 40% of patients and include inflammation (diverticulitis), hemorrhage, intussusception, small-bowel obstruction, stone formation, and neoplasm. The purpose of this article is to familiarize the radiologist with the current imaging of Meckel s diverticulum and its presenting complications. The spectrum of diagnostic findings on various imaging techniques will be reviewed. CONCLUSION. Meckel s diverticulum and its complications are a serious health problem. Familiarity of the radiologist with the appearance of this pathologic entity enables an accurate diagnosis in emergent settings. eckel s diverticulum is the most M common congenital anomaly of the gastrointestinal tract. It is seen in 2% of the population, and it is caused by failure of the omphalomesenteric duct to regress. The point of attachment of a Meckel s diverticulum to the bowel varies. Most (75%) Meckel s diverticula are found within 100 cm of the ileocecal valve [1]. Meckel s diverticulum occurs with equal frequency in both sexes, but symptoms from complications are more common in male patients. Meckel s diverticula are typically asymptomatic and usually are found incidentally, with a lifetime risk of complications reported to be 4 40% [2]. Heterotopic gastric and pancreatic mucosa are frequently found histologically in the diverticula of symptomatic patients [2]. The most common complications are hemorrhage from peptic ulceration, small-intestinal obstruction, and diverticulitis [3]. The purpose of this article is to familiarize the radiologist with the current imaging of Meckel s diverticulum and its presenting complications. The spectrum of diagnostic findings on various imaging techniques will be reviewed. Embryology and natomy Meckel s diverticulum was named after Johann Friedrich Meckel, who described its anatomy and embryology in 1809 [4]. Meckel s diverticulum is a remnant of the omphalomesenteric or vitelline duct, which connects the yolk sac to the midgut through the umbilical cord. This duct is typically obliterated by the 5th 8th week of gestation. Failure of duct closure results in diverticulum (90% of cases), omphalomesenteric fistula, enterocyst, or a fibrous band. Meckel s diverticulum arises from the antimesenteric border of the distal small bowel, typically 40 100 cm from the ileocecal valve, with a typical length of up to 5 cm and diameter of up to 2 cm. lood supply to this diverticulum typically comes from the omphalomesenteric artery (a remnant of the primitive vitelline artery arising from an ileal branch of the superior mesenteric artery). Meckel s diverticula are lined with heterotopic mucosa in up to 60% of cases in the following manner: gastric mucosa, 62%; pancreatic, 6%; both gastric and pancreatic, 5%, jejunal, 2%; runner s glands, 2%; and gastric and duodenal, 2% [5]. Imaging Findings and Usefulness of Various Imaging Techniques Various imaging techniques have been used for diagnosing Meckel s diverticulum. Conventional radiographic examination is of limited value and is usually unrevealing. However, it may show enteroliths, findings of bowel obstruction, and the presence of gas or a gas fluid level in the diverticulum. JR:189, July 2007 81

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 techniques for evaluation of patients with acute symptoms. Meckel s diverticulum is not often seen on routine barium studies because of its small ostium, filling with intestinal contents, and peristalsis with rapid emptying. Meticulous examination with enteroclysis has been reported to be more sensitive [6]. On barium studies, Meckel s diverticulum appears as a blind-ending pouch arising from the antimesenteric side of the distal ileum (Fig. 1). Filling defects in the diverticulum may suggest gastric mucosa or tumor [3]. Meckel s diverticulum may be inverted, serving as lead point for intussusception, and appears as a soft polypoid filling defect [7]. Sonography lthough of limited value, sonography has been used for the investigation of Meckel s diverticulum [8]. High-resolution sonography usually shows a fluid-filled structure in the right lower quadrant having the appearance of a blind-ending, thick-walled loop of bowel, with the typical gut signature and a clear connection to a peristaltic, normal small-bowel loop (Fig. 2). The echo-free contents should not be compressed or expressed into the connecting bowel loop [8]. Hyperechoic mucosa ( gut signature ) is always detected, and enteroliths are visualized as shadowing echogenic foci [8]. CT On CT, Meckel s diverticulum is difficult to distinguish from normal small bowel in uncomplicated cases. However, a blind-ending fluidor gas-filled structure in continuity with small bowel may be seen. CT may also show enteroliths, intussusception, diverticulitis, and smallbowel obstruction. recent innovation of CT enterography has resulted in better visualization of small bowel and consequent higher sensitivity in the diagnosis of Meckel s diverticulum [9] (Fig. 3). CT enterography combines the improved spatial and temporal resolution of MDCT with large volumes of ingested neutral enteric contrast material to permit visualization of the small-bowel wall [9]. ngiography can show the persistent omphalomesenteric artery in most individuals with a Meckel s diverticulum who present with chronic gastrointestinal bleeding (Fig. 4). However, the recognition of a persistent vitellointestinal artery may be difficult because of overlying vessels, and superselective catheterization of distal ileal arteries may be necessary. The omphalomesenteric artery typically arises from mid or distal branches of the superior mesenteric artery. Ectopic gastric mucosa may show a dense blush (Fig. 4). Extravasation of contrast material in cases of active bleeding typically requires bleeding > 0.5 ml/min in order to be visualized [10]. Scintigraphy Scintigraphy with 99m Tc-Na-pertechnetate has only minor diagnostic value and a limited sensitivity of 60% in diagnosing Meckel s diverticulum [11]. However, it aids in the diagnosis of diverticula with ectopic gastric mucosa. Pertechnetate is taken up by mucinsecreting cells of the gastric mucosa and ectopic gastric tissue. Higher sensitivity in pediatric (85 90%) than in adult (60%) patients is noticed [11]. This could be due to earlier symptoms (such as hemorrhage) in patients with ectopic gastric mucosa (Fig. 5). Imaging of Complications of Meckel s Diverticulum Reported complication rates range from 4% to 40%, with complications including bleeding, bowel obstruction, enterolith formation, retention of foreign bodies, inflammation (diverticulitis or ulceration), and neoplasm [2, 5, 12]. Detection of heterotopic gastric mucosa is of paramount significance because it can result in serious complications such as bleeding. CT and scintigraphy play an important role in the diagnosis of heterotopic mucosa (Figs. 5 and 6). Hemorrhage Hemorrhage accounts for up to 30% of symptomatic Meckel cases [12]. Hemorrhage usually occurs secondary to ectopic gastric mucosa. Hemorrhage has been reported to be more common and more severe during childhood. ngiography is usually used to diagnose hemorrhage secondary to the bleeding Meckel s diverticulum (Fig. 4). owel Obstruction owel obstruction accounts for up to 40% of symptomatic Meckel s diverticula [12] (Fig. 7). Obstruction can be caused by trapping of a bowel loop by a mesodiverticular band, a volvulus of the diverticulum around a mesodiverticular band (Fig. 8), and intussusception, as well as by an extension into a hernia sac (Littre s hernia). Obstruction has been found to occur more frequently with a giant Meckel s diverticulum. MDCT is a sensitive technique for diagnosing small-bowel obstruction [13]. Ileocolonic intussusception can rarely occur secondary to an invaginated Meckel s diverticulum. In these cases, CT reveals dilated loops of proximal small bowel with an intraluminal mass seen in the ascending colon. This intracolonic mass is an intussuscepted ileum [14] (Fig. 9). Enterolith Formation Enterolith formation is an uncommon complication of Meckel s diverticulum despite diverticula being the most likely sites of a smallbowel enterolith. Enteroliths can be seen in 3 10% of Meckel s diverticula [12]. Enteroliths are thought to form as a result of stasis. pproximately 50% of enteroliths can be seen on radiography. However, unenhanced CT should be more valuable in detecting an enterolith (Figs. 10 and 11). Inflammation Diverticulitis accounts for up to 30% of symptomatic cases [12]. Diverticulitis commonly occurs secondary to acid secretion from ectopic gastric mucosa. It also can occur due to obstruction by enteroliths, foreign bodies, or neoplasm. Scintigraphy has been used for diagnosing Meckel s diverticulitis secondary to heterotopic gastric mucosa and usually shows a focal high uptake indicative of heterotopic gastric mucosa with an adjacent region of low-grade tracer localization attributable to the inflammatory mass [15]. CT is a sensitive technique for diagnosing Meckel s diverticulitis, which usually appears as a blind-ending pouch of variable size with mural thickness and containing fluid, air, or particulate material with surrounding mesenteric inflammation [16] (Figs. 10 and 12). Neoplasm Neoplasms arising in Meckel s diverticula are rare, accounting for up to 3% of complicated cases [14]. The most frequently reported neoplasm complicating a Meckel s diverticulum is carcinoid tumor. Other reported tumors include leiomyoma (Fig. 13), leiomyosarcoma [17], angioma, neuroma, lipoma, carcinosarcoma, and adenocarcinoma [18, 19]. These tumors have nonspecific imaging features, including a sessile or lobulated filling defect. Malignant neoplasms may infiltrate the adjacent mesenteric fat [19]. Perforation Meckel s diverticulum can rarely be complicated by perforation, which is a serious health 82 JR:189, July 2007

Imaging of Meckel s Diverticulum event. Perforation is usually secondary to inflammatory diverticulitis, gangrene, and peptic ulceration [20 22]. Perforation can be suggested by the presence of free intraperitoneal air in the setting of Meckel s diverticulum. This can be further detected on CT (Fig. 14). Conclusion Meckel s diverticulum and its complications are a serious health problem. Familiarity of the radiologist with the appearance of this pathologic entity enables an accurate diagnosis in emergent settings. References 1. Satya R, O Malley JP. Meckel diverticulum with massive bleeding. Radiology 2005; 236:836 840 2. Fink M, lexopoulou E, Carty H. leeding Meckel s diverticulum in infancy: unusual scintigraphic and ultrasound appearances. Pediatr Radiol 1995; 25:155 156 3. Levy D, Hobbs CM. From the archives of the FIP. Meckel diverticulum: radiologic features with pathologic correlation. RadioGraphics 2004; 24:565 587 4. Opitz JM, Schultka R, Gobbel L. Meckel on developmental pathology. m J Med Genet 2006; 140:115 128 5. Matsagas MI, Fatouros M, Koulouras, Giannoukas D. Incidence, complications and management of Meckel s diverticulum. rch Surg 1995; 130:143 146 6. Maglinte DD, Elmore MF, Isenberg M, Dolan P. Meckel diverticulum: radiologic demonstration by enteroclysis. JR 1980; 134:925 932 7. Hori K, Suzuki Y, Fujimori T. Inverted Meckel s diverticulum. Surgery 2003; 133:116 117 8. Mostbeck GH, Liskutin J, Dorffner R, et al. Ultrasonographic diagnosis of a bleeding Meckel s diverticulum. Pediatr Radiol 2000; 30:382 9. Paulsen SR, Huprich JE, Fletcher JG, et al. CT enterography as a diagnostic tool in evaluating small bowel disorders: review of clinical experience with over 700 cases. RadioGraphics 2006; 26:641 657 10. Mitchell W, Spencer J, llison DJ, et al. Meckel s diverticulum: angiographic findings in 16 patients. JR 1998; 170:1329 1333 11. Poulsen K, Qvist N. Sodium pertechnetate scintigraphy in detection of Meckel s diverticulum: is it usable? Eur J Pediatr Surg 2000; 10:228 231 12. Kusomoto H, Yoshida M, Takahashi I., et al. Complications and diagnosis of Meckel s diverticulum in 776 patients. m J Surg 1992; 164:382 383 13. ufort S, Charra L, Lesnik, et al. Multidetector CT of bowel obstruction: value of post-processing. Eur Radiol 2005; 15:2323 2329 14. Konstantakos K. Meckel s diverticulum induced ileocolonic intussusception. m J Surg 2004; 187:557 558 15. Connolly S, Drubach L, Connolly LP. Meckel s diverticulitis: diagnosis with computed tomography and Tc-99m pertechnetate scintigraphy. Clin Nucl Med 2004; 29:823 824 16. ennett GL, irnbaum, althazar EJ. CT of Meckel s diverticulitis in 11 patients. JR 2004; 182:625 629 17. Saadia R, Decker G. Leiomyosarcoma of Meckel s diverticulum: a case report and review of the literature. J Surg Oncol 1986; 32:86 88 18. Yamaguchi K, Maeda S, Kitamura K. denocarcinoma in Meckel s diverticulum: case report and literature review. ust N Z J Surg 1989; 59:811 813 19. Kusumoto H, Yoshitake H, Mochida K, Kumashiro R, Sano C, Inutsuka S. denocarcinoma in Meckel s diverticulum: report of a case and review of 30 cases in the English and Japanese literature. m J Gastroenterol 1992; 87:910 913 20. aldisserotto M. Color Doppler sonographic findings of inflamed and perforated Meckel diverticulum. J Ultrasound Med 2004; 23:843 848 21. Schmidt C, rown L, Klomp H, et al. Perforated Meckel s diverticulum. Surgery 2001; 129:643 644 22. Jelenc F, Strlic M, Gvardijancic D. Meckel s diverticulum perforation with intraabdominal hemorrhage. J Pediatr Surg 2002; 37:E18 Fig. 1 Image from small-bowel follow-through examination shows filling of blind-ending diverticulum (arrow) in right lower quadrant in 17-year-old girl with chronic abdominal pain. Fig. 2 Sonogram in 30-year-old woman shows blind-ending thickened loop with gut signature correlating with inflamed Meckel s diverticulum (short arrow) in right lower quadrant. Note cecum (long arrow) and iliac vessels (arrowhead). Fig. 3 37-year-old man with occult gastrointestinal bleeding. xial image from CT enterography examination shows increased enhancement in Meckel s diverticulum (arrow). Surgical pathology confirmed ectopic gastric mucosa. JR:189, July 2007 83

Fig. 4 17-year-old girl with abdominal pain and rectal bleeding. and, Selective angiograms of superior mesenteric artery show focal region of pooling surrounding Meckel s diverticulum with contrast blush (arrow). C D Fig. 5 26-year-old woman with Meckel s diverticulum. D, Technetium-99m-labeled heat-damaged RC scans show focus of intense activity (arrows, D) in right lower quadrant on initial flow study. Operative findings confirmed hemorrhagic Meckel s diverticulum. 84 JR:189, July 2007

Imaging of Meckel s Diverticulum Fig. 6 26-year-old woman. xial contrast-enhanced CT scan shows blind-ending Meckel s diverticulum with thickened mucosal folds (arrow). Pathology confirmed ectopic gastric mucosa in Meckel s diverticulum. Fig. 7 23-year-old man. and, xial contrast-enhanced CT images show blind-ending fluid-filled structure (arrow, ) resulting in small-bowel obstruction. Operative findings confirmed Meckel s diverticulum. Fig. 8 21-year-old woman with right lower quadrant pain and neutrophilia. and, xial CT scans show U-shaped loop of bowel in pelvis, suggesting volvulus of diverticulum around mesodiverticular band (arrow). Operative findings confirmed torsion of Meckel s diverticulum. JR:189, July 2007 85

Fig. 9 13-year-old boy with right lower quadrant abdominal pain. and, CT scans reveal long-segment enteroenteric intussusception due to inverted Meckel s diverticulum (arrow, ). Fig. 10 31-year-old woman. and, xial CT scans show enterolith (arrow, ) in dilated infected Meckel s diverticulum. Note adjacent infiltration of ileocolic mesentery, suggesting superimposed diverticulitis (arrows, ). Fig. 11 28-year-old woman with vomiting and abdominal pain., xial CT scan reveals distended fluid-filled diverticulum (arrow) with narrowed neck., CT scan shows enteroliths (arrow) in neck of diverticulum. Operative findings confirmed obstructed Meckel s diverticulum containing enterolith. 86 JR:189, July 2007

Imaging of Meckel s Diverticulum Fig. 12 28-year-old man with 1 week of epigastric pain that subsequently localized to right lower quadrant. C, CT scans show inflammatory process in right lower quadrant (arrows, ) with small abscess (arrow, and C). Operative exploration confirmed perforated Meckel s diverticulitis. Fig. 13 37-year-old woman with melena. Technetium- 99m-labeled RC study shows bleeding in right lower quadrant (arrow). Operative findings confirmed Meckel s diverticulum with ulcerated leiomyoma (thought to be cause of bleeding). C JR:189, July 2007 87

C Fig. 14 34-year-old man. C, Serial CT slices through lower abdomen show perforated Meckel s diverticulum (black arrow, ). Extraluminal gas (arrow, ), and inflammatory changes (white arrow, ) are seen adjacent to diverticulum. Operative findings confirmed imaging findings. FOR YOUR INFORMTION This article is available for CME credit. See www.arrs.org for more information. 88 JR:189, July 2007