Bowel / IBD (Crohn) — Reference values

Bowel / IBD (Crohn) — Reference values: Bowel wall thickness, Calculator — appendicitis (US + Alvarado), Activity signs (Crohn on US).

Measurements and reference values

Measurement	Usual value	Note
Bowel wall thickness	≤ 3 mm	> 3 mm suggests inflammation (sens. 89% / spec. 96%)Source: Abdom Radiol / PMC

Classifications and calculators

Calculator — appendicitis (US + Alvarado)

Finding	Reading
Appendix <6 mm, compressible	Usually normal.
6–7 mm or not visualized	Borderline: weigh secondary signs; non-visualization does not exclude.
≥7 mm non-compressible + signs	Appendicitis likely (inflamed fat, hyperemia, appendicolith).
Periappendiceal collection/fluid	Suspected perforation/abscess.

Alvarado: migratory pain (1), anorexia (1), nausea (1), RLQ tenderness (2), rebound (1), fever (1), leukocytosis (2), left shift (1). ≥7 = high probability; 5–6 = observe; ≤4 = low.

Source: ACR appropriateness / Alvarado 1986 / SPR pediatric US

Activity signs (Crohn on US)

Sign	Finding
Wall	Thickness > 3 mm
Vascularity	Hypervascularity (Limberg ≥ 2)
Mesenteric fat	Proliferation/inflammation (creeping fat)
Complications	Lymph nodes, stricture, fistula, abscess, ascites

Source: Intestinal US in IBD (PMC)

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