Diagnostic Ultrasound - Abdomen and Pelvis

Crohn Disease
TERMINOLOGY
Synonyms
• Terminal ileitis, regional enteritis, ileocolitis
Definitions
• Chronic, relapsing granulomatous inflammatory disease
with predominant involvement of gastrointestinal tract
IMAGING
General Features
• Best diagnostic clue
○ Bowel wall thickening
– Adults: > 3 mm
– Children: Small bowel thickness > 2.5 mm and large
bowel wall thickness > 2 mm
• Location
○ From mouth to anus
– Involvement: Terminal ileum (95%), colon (22-55%),
rectum (14-50%)
□ Small bowel alone (30-35%), small bowel and colon
(50-60%), colon alone (20%)
– Increased small bowel involvement in younger
patients (80% vs. 60%)
○ Look for skip lesions: Normal bowel between areas of
involved bowel
Ultrasonographic Findings
• Grayscale ultrasound
○ Mural
– Bowel wall thickening
– Increased or decreased echogenicity of bowel wall
– Loss of normal bowel wall stratification
– Ulceration
– Fistula/sinus tract
– Intramural abscess
– Luminal narrowing
– Postinflammatory polyps can form during healing of
extensive ulcerative disease
○ Extramural
– Thickening/increased echogenicity of mesentery
– Separation of bowel loops
– Fistulas (enteroenteric, enteromesenteric,
enterocutaneous, enterovesical, enterovaginal)
– Lymphadenopathy
– Phlegmon/abscess
○ Decreased/absent peristalsis of involved bowel
• Color Doppler
○ Hyperemia of bowel wall and mesentery
– Correlates with disease activity as angiogenesis and
inflammation are directly correlated
• Contrast material-enhanced ultrasonography
○ Improves sensitivity for detecting inflammation
○ Objective quantification for assessing degree of
inflammation and for follow-up
• Elastography
○ Able to detect changes of fibrosis in affected bowel wall
segments
Fluoroscopic Findings
• Upper GI/small bowel series
○ Aphthous ulcers: Earliest macroscopic change, central
punctate barium with surrounding edema (target/bull's
eye)
○ Cobblestone appearance: Linear and transverse ulcers
with spared surrounding mucosa (pseudopolyps)
○ Luminal narrowing, ulceration; penetrating disease:
Fistula or sinus tract
CT Findings
• CECT or CT enterography (CTE)
○ Wall thickening
○ Engorgement of vasa recta ("comb" sign)
○ Inflammation in mesentery
○ Reactive lymphadenopathy
○ Penetrating disease: Fistulae, sinus tracks,
phlegmon/abscess
○ Luminal narrowing ± obstruction
○ Perianal disease
○ Enhancement of bowel wall; "target" or "double halo"
sign
MR Findings
• MR enterography (MRE)
○ Similar findings to CT but without using ionizing radiation
○ Can assess peristalsis on free-breathing coronal
sequences
○ Useful in evaluating perianal involvement
Imaging Recommendations
• Best imaging tool
○ Undiagnosed or suspected patients stratified into high or
low risk based on symptoms, laboratory values, physical
exam, and family history
– Low risk: Ultrasound or MRE recommended
– High risk: MRE or CTE
○ Newly diagnosed patients
– MRE or CTE
○ Patients with established diagnosis of Crohn disease
– Acute/emergent assessment: CT
– Monitoring/longstanding complications: MRE
• Protocol advice
○ Ultrasound
– High-resolution, high-frequency linear transducer (>
10 MHz)
□ Convex transducer for better penetration as
needed (3-8 MHz)
– Encourage clear, noncarbonated beverages prior to
exam to help distend bowel
– Graded compression
– Harmonic imaging: Wide band preferred
– Clips for assessment of bowel motility
DIFFERENTIAL DIAGNOSIS
Infectious Colitis
• Shigella, Salmonella, Campylobacter, Escherichia coli O157:H,
Yersinia, parasites, amebiasis
• Clostridium difficile if recent antibiotic use
• Cytomegalovirus in immunocompromised patients
• Tuberculosis: Narrowed terminal ileum and cecum
Diagnoses: Bowel
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