Work-up for Thickened Small Bowel Loops
Obtain a contrast-enhanced CT enterography (CTE) or MR enterography (MRE) immediately as the primary diagnostic tool to establish the cause, assess for complications requiring surgery, and guide management. 1
Initial Clinical Assessment
Perform a focused evaluation looking specifically for:
- Signs of peritonitis (rebound tenderness, guarding, rigidity) which mandate immediate surgery 1
- Vital sign abnormalities including fever, tachycardia, hypotension suggesting sepsis or ischemia 1
- Abdominal distension and abnormal bowel sounds (absent or high-pitched) 2, 3
- Previous abdominal surgery history which increases likelihood of adhesive disease 3
- All hernia orifices to identify incarcerated hernias 2
Laboratory Investigations
Order the following tests immediately:
- Complete blood count looking for leukocytosis with left shift suggesting inflammation or ischemia 1, 2
- C-reactive protein (CRP) and lactate as elevated levels indicate peritonitis or bowel ischemia 1, 2
- Comprehensive metabolic panel including electrolytes, BUN/creatinine, and liver function tests 1, 2
- Stool studies including Clostridium difficile toxin and other infectious causes 1
Imaging Strategy
Primary Imaging: CT or MR Enterography
CT enterography with IV contrast is the gold standard for evaluating thickened small bowel loops, providing 87-90% accuracy for determining etiology 1. The study should be performed in the enteric to portal venous phase of enhancement 1.
Key imaging findings to identify:
For inflammatory conditions (Crohn's disease most likely):
- Asymmetric mural hyperenhancement with wall thickening >3mm strongly suggests Crohn's disease when combined with mesenteric findings 1
- Stratified (bi- or tri-laminar) enhancement pattern due to submucosal edema or intramural fat 1
- Mural ulcerations appearing as focal breaks in the bowel wall 1
- Mesenteric stranding and lymphadenopathy 1
For obstruction:
- Transition point with upstream dilation >3cm indicating mechanical obstruction 1, 2
- Closed-loop obstruction pattern with U-shaped dilated loops and extraluminal fluid requiring immediate surgery 1, 4
- Small bowel feces sign predicting need for surgery 1
For ischemia (surgical emergency):
- Mesenteric edema and free intraperitoneal fluid 1
- Pneumatosis intestinalis or portal venous gas 5
- Lack of mural enhancement suggesting necrosis 1
MRE Advantages Over CTE
Consider MRE over CTE when:
- Young patients requiring serial monitoring to avoid radiation exposure 1, 6
- Pregnancy 1
- Multiparametric assessment needed including T2 hyperintensity and diffusion restriction which correlate with moderate-to-severe inflammation 1
If IV contrast is contraindicated, noncontrast MRE with T2-weighted and diffusion-weighted imaging is an acceptable alternative 1.
Ultrasound Role
Ultrasound in skilled hands can identify thickened small bowel loops, assess peristalsis, and detect free fluid or abscesses 1, 7. Bedside ultrasound by emergency physicians has excellent diagnostic accuracy with a positive likelihood ratio of 9.55 3. However, ultrasound should not replace CT/MRE for definitive diagnosis 1.
Differential Diagnosis Based on Imaging Pattern
Focal Thickening (<5cm)
Irregular, asymmetric thickening suggests:
- Malignancy (adenocarcinoma, lymphoma, carcinoid) requiring biopsy 8
- Extension into adjacent mesentery >1.5cm diameter indicates mass 1
Symmetric thickening with disproportionate fat stranding suggests:
- Inflammatory conditions (Crohn's disease, diverticulitis) 8
Segmental/Diffuse Thickening (>5cm)
With stratified enhancement:
- Crohn's disease - asymmetric, skip lesions, mesenteric involvement 1
- Infectious enteritis - symmetric, diffuse 8
With homogeneous enhancement:
- Ischemia - symmetric, vascular territory distribution 8
- Vasculitis 1
- Edema from hypoalbuminemia or heart failure 8
Endoscopic Evaluation
Ileocolonoscopy Indications
Perform colonoscopy with terminal ileal intubation and biopsy when:
- Crohn's disease is suspected to document extent, obtain histology, and assess for dysplasia 1
- Mild-to-moderate disease is present (defer in severe disease due to perforation risk) 1
- Colonic involvement needs assessment as CTE/MRE with only oral contrast cannot adequately stage colonic inflammation 1
Obtain terminal ileal biopsies even if macroscopically normal to detect microscopic Crohn's disease 1.
Capsule Endoscopy
The role remains unclear and should not be used as first-line investigation 1. Consider only after negative ileocolonoscopy and cross-sectional imaging in suspected small bowel Crohn's disease.
Additional Specialized Studies
Small bowel follow-through or enteroclysis is inferior to CTE/MRE and generally not recommended 1.
White cell scanning lacks specificity and is not routinely recommended 1.
Dedicated pelvic MRI is required if perianal Crohn's disease is suspected 1.
Critical Decision Points
Immediate Surgery Required If:
- Clinical peritonitis on examination 1, 5
- CT findings of closed-loop obstruction 1, 5
- Bowel ischemia (pneumatosis, portal venous gas, lack of enhancement) 1, 5
- Free perforation 5
Consider Other Diagnoses
Tuberculosis, Behçet's disease, lymphoma, and vasculitis can mimic Crohn's disease with ileal thickening 1. In endemic areas or appropriate clinical context, laparoscopy may be necessary to differentiate intestinal tuberculosis from Crohn's disease 1.
Common Pitfalls to Avoid
- Do not rely on plain radiography alone - sensitivity is only 60-70% for small bowel obstruction 2, 3
- Do not delay CT if clinical suspicion is high - traditional clinical-radiographic evaluation misses 54% of complete obstructions 9
- Do not assume imaging inflammation equals clinical activity - there is correlation but not equivalence between imaging, endoscopic, and histologic findings 1
- Do not miss mesenteric venous thrombosis - carefully evaluate all CTE/MRE for venous occlusions and small bowel varices 1
- Do not perform flexible sigmoidoscopy alone in suspected Crohn's disease - colonoscopy to terminal ileum is required 1