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Mucosal thickening refers to an increase in the thickness of the bowel wall as visualized on cross-sectional imaging (CT, MRI, or ultrasound).
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It is a nonspecific radiologic sign that may result from a broad spectrum of inflammatory, infectious, ischemic, neoplastic, or systemic conditions.
Understanding the pattern, symmetry, extent, and associated findings is crucial for narrowing the differential diagnosis.
Normal Bowel Wall Thickness
| Segment | Thickness (distended) | Notes |
|---|---|---|
| Small bowel | ≤3 mm | Jejunum > ileum in folds (valvulae conniventes) |
| Colon | ≤5 mm | Varies by distension |
| Rectum | ≤6 mm | May appear thicker if collapsed |
Bowel wall thickening occurs due to one or more of the following mechanisms:
When evaluating bowel wall thickening on CT/MRI, assess:
| Feature | Interpretation Clues |
|---|---|
| Thickness | Mild (<1 cm) → benign; Marked (>2 cm) → neoplastic/infectious |
| Symmetry | Symmetric → inflammatory/ischemic; Asymmetric → neoplastic |
| Length of involvement | Long segment (>6 cm) → inflammatory/ischemic; Short (<5 cm) → tumor |
| Enhancement pattern | Homogeneous (tumor/fibrosis); Stratified “target” pattern (inflammation/edema/ischemia) |
| Perienteric changes | Fat stranding, abscess, fistula – inflammatory; Clean mesentery – neoplastic |
| Associated features | Lymphadenopathy, ascites, vascular changes, pneumatosis, obstruction |
Key differentials:
| Etiology | Pattern | Length | Enhancement | Key Features |
|---|---|---|---|---|
| Inflammatory (Crohn’s, UC) | Symmetric | Long | Stratified | Comb sign, creeping fat |
| Infectious | Symmetric | Long | Stratified | Nodes, fat stranding |
| Ischemic | Symmetric | Segmental | Stratified or poor | Thumbprinting, pneumatosis |
| Neoplastic (AdenoCa) | Asymmetric | Short | Homogeneous | Obstruction, necrotic nodes |
| Lymphoma | Symmetric | Long | Homogeneous | Aneurysmal dilatation, bulky nodes |
| TB | Asymmetric | Ileocecal | Rim-enhancing nodes | Pulled-up cecum |
| Edema / Hypoproteinemia | Symmetric | Diffuse | Mild | No enhancement, systemic signs |