Bowel Wall Thickening in Children: CT Findings

1. In the name of God Bowel Wall Thickening in Children: CT Findings H. Bahrami

2. Point: • The differential diagnosis for diseases affecting the bowel in pediatric patients can be narrowed by paying attention to specific radiologic signs and the patient’s clinical history

3. Technical Considerations: • We obtain 5-mm-thick axial images that are routinely retrospectively reformatted in the coronal plane • If the patient is less than 6 months old, we obtain 3.75-mm-thick axial images • No routine acquisition of delayed images

4. Timing: • If sedation is required, oral contrast material is administered approximately 15–20 minutes before placing the child on the CT table plus the time required to sedate the child, accounts for the 40–45 minutes just prior to the actual scanning • When sedation is not required, patients are scanned 1 hour after the ingestion of oral contrast material

5. Oral Contrast: • Omnipaque mixed with Gatorade (Quaker Oats, Chicago, Ill) is offered initially to children • Besides being nonionic, iohexol is tasteless and has a thinner consistency, increasing patient compliance • In addition, we have noticed a faster transit time, yielding better enhancement of more distal portions of the colon and sometimes even of the rectum • When there is a history of iodine allergy, the child is offered flavored barium suspension

6. Negative contrast agent: • We also use cold water as a negative contrast agent more frequently in children who refuse other oral contrast agents and when the evaluation of the mucosa is most important, such as in graft-versus-host disease (GVHD) and vasculitis • Cold water is better tolerated when nausea is present; however, it makes the timing of the study more challenging because of its rapid absorption through the bowel and the lack of colonic distention

7. Negative contrast agent disadvantages: • Water makes the wall of the bowel more conspicuous and may give the false impression of mild thickening • Fistulous tracts • Acute appendicitis An appendix filled with a positive contrast agent is easier to recognize and virtually excludes appendicitis

8. False impression of mild wall thckening:

10. Findings: • Recognizing the presence and degree of bowel wall thickening is of the utmost importance • Some authors have described the normal bowel wall thickness in adults as 1–2 mm when the lumen is distended • Colonic wall thickness is more dependent on distention and intraluminal contents than is small • To our knowledge, there are no published standards of normal bowel wall thickness in children

11. Findings: • As a practical general rule, the bowel wall should be barely perceptible when adequately distended • When a peristaltic loop is imaged, transient wall thickening is present, usually posing no diagnostic dilemma at CT • Depending on the degree of bowel wall thickening, luminal narrowing may lead to proximal bowel dilatation

13. Severity: • Pseudomembranous colitis and Crohndisease tend to be associated with the most severe wall thickening

14. Crohn disease:

15. Distribution: • Either the small bowel, the large bowel, or both • Focal (only a few centimeters), segmental (usually a few bowel loops), diffuse (either the entire small bowel or large bowel), or universal (the entire small and large bowel)

16. Pattern: • Eccentric involvement is more commonly seen with tumors, either benign or malignant • Whereas circumferential thickening tends to occur with inflammatory conditions and infections • One exception to this rule is the “apple core” sign, which represents luminal narrowing resulting from focal circumferential wall thickening of the bowel

17. Wall attenuation: • A hyperattenuatingwall is seen with hemorrhage as a result of trauma, purpura, or vasculitis • A sub mucosal fatty “halo” has been described as a result of chronic inflammation, such as in inflammatory bowel disease and GVHD • A fatty halo has also been reported in asymptomatic obese patients

18. Long-standingulcerative colitis:

19. history of BMT who was receiving steroids:linear subserosal mural air

20. Pneumatosisintestinalis: • Intramural gas may have a different appearance, depending on whether it is submucosalor subserosal; • The former is bubbly or cystic in appearance and the latter is curvilinear

21. Pneumatosisintestinalis: More than 50 causes; • Ischemia • Rotavirus gastroenteritis • Bowel obstruction such as pyloric stenosisand meconiumileus • Accidental and non-accidental trauma • Steroids • Chemotherapy • Organ transplantation • Cystic fibrosis and asthma

22. Target sign, mural stratification:

23. Submucosal edema is definitive evidence of bowel wall injury (typically acute), often producing the “target” sign • Mural stratification is due to hypoattenuatingsubmucosaledema, with the enhancing hyperattenuating inner and outer layers of the target representing the mucosa and muscularispropria–serosa, respectively

25. The “accordion” sign: • Is caused by contrast material trapped between thickened edematous haustral folds in the colon • Although the accordion sign is most commonly seen in pseudomembranouscolitis, it is not pathognomonic for this disease

27. The “comb” sign: • Represents hypervascular engorged vasa recta aligned like the teeth of a comb on the mesenteric site of the bowel • This finding is classically seen in inflammatory bowel disease, especially Crohn disease, and suggests a clinically active disease • Can also be seen in vasculitis and purpura

29. The “toothpaste” or “lead pipe” sign: • Associated with chronic diseases leading to a “featureless” bowel • It is commonly seen with Crohn disease or chronic GVHD or as the sequelaof radiation therapy

30. Homosexual teenager:

31. Infection: • Gastroenteritis and colitis are probably the most common causes of bowel wall thickening and are usually diagnosed clinically • Occasionally, however, they are identified at CT, either incidentally or as an atypical manifestation • It is difficult to make the diagnosis of a specific type of infection on the basis of imaging findings alone

32. Most of the bacterial colitidestend to involve the right colon • Certain ancillary signs such as lymphadenopathyand splenomegalysuggest Salmonella • Diffuse involvement suggests E coli or Cytomegalovirus • The rectosigmoidcolon tends to be involved with Herpes, Neisseriagonorrhoeae, and Treponemapallidumas part of the so-called gay bowel syndrom

34. Pseudomembranous Colitis. • Extreme segmental or diffuse wall thickening • The degree of wall thickening is greater than in any other infectious or inflammatory process involving the bowel except for Crohndisease • The so-called accordion sign is suggestive of but not pathognomonicfor this entity and is usually seen in advanced cases • Typically, no significant pericolonicfat stranding is seen

35. Diffuse concentric colonic wall thickening:

36. E coli Infection. • In children may result in HUS • Is the most common cause of acute renal failure in children • The cecumand ascending colon are the most commonly involved areas • CT findings include mural stratification, narrowing of the bowel lumen, and pericolonicfat stranding • Colonic ischemia and perforation are well-known complications

38. Trauma: • The duodenum and small bowel are commonly injured after trauma • Typically, duodenal hematomas are intramural, involving the second or third portion of the duodenum • The characteristic finding is an eccentric mass protruding into the bowel lumen and causing varying degrees of obstruction • In acute trauma, the mass tends to be slightly hyperattenuating • Localized enhancing wall thickening is usually present

40. Hypoperfusion complex–shock bowel syndrome: • Is the manifestation of a tenuous hemodynamic instability, usually secondary to trauma even after aggressive resuscitation efforts with intravenous fluid • CT findings include dilated and fluid-filled small bowel loops with sparing of the colon • The small bowel wall is thickened in a diffuse and concentric fashion, displaying intense enhancement after contrast material administration

41. Lymphoma: • Secondary bowel involvement from generalized lymphomas is more common than primary lymphoma • T-cell lymphomas of the bowel include plaques, mucosal ulceration, and strictures • B-cell type lymphoma manifests as polypoid masses or eccentric wall thickening

42. Lymphoma: • Aneurysmal dilatation secondary to destruction of the autonomic nerve plexus by tumor infiltration can be seen • The presence of hepatosplenomegaly and hypoattenuating bulky adenopathy are supporting findings • Both the small bowel and colon are involved; however, B-cell lymphomas tend to affect the distal ileum, whereas T-cell types affect the duodenum and jejunum

43. Intussusceptioncontainsmesenteric fat (arrow), manifestation of lymphoma

44. A large, low-attenuation eccentric mass with intense peripheral enhancement (arrow)

45. Gastrointestinal stromaltumors: • The most common mesenchymalneoplasms of the gastrointestinal tract • The most common site of involvement is the stomach, followed by the small intestine • These tumors arise from the muscularispropria, typically manifesting as an eccentric well-circumscribed mass, occasionally with a hypoattenuating center representing cystic degeneration or necrosis

46. Hemangioma: • Seldom involve the gastrointestinal tract • Most hemangiomas are pedunculated, intraluminalpolypoid lesions; occasionally, they may have an infiltrative growth pattern • If there is diffuse involvement, the term hemangiomatosisshould be used • The small bowel is the most commonly affected site, with jejunalpredominance

48. CT findings include diffuse infiltration of the intestinal wall with mural thickening and occasional phleboliths • A hyperattenuating, markedly enhancing bowel wall is a classic finding

50. Colon Cancer. • Arising from the mucosa • Rare in the pediatric age group but can occasionally manifest in the 2nd decade of life • The transverse colon and the rectosigmoid are the two most commonly affected sites • Radiologic features including polypoid, ulcerative, annular constricting (apple core sign) and scirrhous carcinomas