[size=20px]An 11-year old boy diagnosed three years ago with terminal ileal Crohn disease presents with a four day history of diffuse abdominal pain, decreased oral intake and emesis. Over the last 12 months he has required several admissions for similar presentations and a infliximab regimen was started two months ago. The physical exam is significant for distended abdomen with mild tenderness but no signs of peritonitis. The preferred noninvasive imaging modality to distinguish a Crohn disease flare up from chronic stricture is

 

a abdominal ultrasonography.

 

b barium small bowel follow through.

 

c computerized tomographic enterography.

 

d magnetic resonance enterography.

 

e capsule endoscopy.[/size]

D

D

D

D

D

E

C

Correct answer

D magnetic resonance enterography.

 

As the incidence of inflammatory bowel disease in children continues to increase, a reliable, accurate and radiation free imaging modality is needed since these patients will require multiple imaging exams throughout their lifetime. The distal small bowel can be difficult to assess with plain films, standard contrast studies, and endoscopy. Magnetic resonance enterography is a noninvasive imaging modality lacking ionizing radiation and is currently the preferred imaging modality in pediatric inflammatory bowel disease. It can detect inflammatory changes in the intestinal wall and complications such as fistula, abscess and stenosis. The presence of a small bowel stricture (i.e. thickened intestinal wall, narrowed luminal diameter and prestenotic dilatation) with a hypointense bowel wall and no significant contrast enhancement indicates a long standing fibrotic stricture, rather than an acute flare up, which would not benefit from further medical treatment.

 

A 2017 systematic review and meta-analysis of 18 articles including 687 patients found a sensitivity of 83% and a specificity of 93% for magnetic resonance enterography using histopathology as the reference standard in pediatric and adolescent inflammatory bowel disease patients. A 2019 systematic literature review confirmed the findings and recommended MRE as the preferred technique.

 

Small bowel follow through is time consuming, limited in assessing extraintestinal complications, operator and patient dependent leading to decreased sensitivity and exposes the patient to ionizing radiation.

 

Ultrasonography has the advantage of being radiation free, low cost and widely available. It may serve as a screening modality for Crohn disease. Ultrasound does not allow for comprehensive examination of the small bowel, can be limited by intervening bowel gas, obesity and abdominal pain in addition to decreased interobserver agreement in mid- and proximal small bowel imaging.

 

Computerized tomographic enterography is a fast study and can reliably demonstrate mural and extraintestinal disease. However, the need for repeated imaging in a disease such as Crohn disease with a life long chronic relapsing course may lead to a concerning cumulative radiation dose.

 

Capsule endoscopy can directly visualize the small bowel mucosa but cannot evaluate extraintestinal disease and should not be used in stricturing disease as capsule retention requiring surgical exploration may occur in patients with significant luminal narrowing.