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Abdomen and PelvisDemonstration data

CT Enterography

CT enterography (CTE) is a dedicated small bowel examination that combines large-volume neutral oral contrast with intravenous contrast to distend and evaluate the small bowel wall and mesentery. It is a first-line cross-sectional test for suspected and known Crohn disease, providing both luminal and extraluminal assessment in a single acquisition.

Indications

  • Known or suspected Crohn disease for detection and grading of active inflammation
  • Assessment of penetrating complications: fistula, sinus tract, phlegmon and abscess
  • Small bowel obstruction of suspected inflammatory or neoplastic aetiology
  • Obscure or occult gastrointestinal bleeding after negative endoscopy
  • Characterisation of suspected small bowel tumour (e.g. carcinoid, GIST, lymphoma)

Contraindications & Cautions

  • Severe iodinated contrast allergy without adequate premedication
  • Significant renal impairment limiting intravenous contrast administration
  • Complete or high-grade bowel obstruction where oral contrast ingestion is unsafe or precluded by vomiting
  • Pregnancy (relative; weigh ionising radiation against alternatives such as MR enterography)

Patient Preparation

  • Fasting for approximately 4-6 hours prior to examination
  • Ingestion of 1350-2000 mL neutral oral contrast (e.g. 0.1% barium sulphate or polyethylene glycol solution) over 45-60 minutes
  • Final aliquot of oral contrast immediately before scanning to distend proximal small bowel
  • Confirm renal function and screen for iodinated contrast allergy before intravenous injection

Technique & Parameters

  • Supine positioning with scan coverage from diaphragm to symphysis pubis
  • Intravenous contrast 100-150 mL at 3-4 mL/s with enteric-phase imaging at approximately 45-50 seconds
  • Thin collimation (≤1.25 mm) reconstructed as 2-3 mm axial and coronal images
  • Consider low kVp (e.g. 80-100) or spectral technique to accentuate mural hyperenhancement and reduce dose
  • Antispasmodic administration is optional and not routinely required for CTE

Systematic Review

  • Evaluate luminal distension segment by segment (duodenum, jejunum, ileum, terminal ileum)
  • Assess mural thickness, degree and pattern of enhancement, and mural stratification
  • Inspect mesentery for engorged vasa recta (comb sign), fibrofatty proliferation and lymphadenopathy
  • Search for penetrating disease: fistulae, sinus tracts, inflammatory masses and abscess
  • Review solid organs, vasculature and osseous structures for extraintestinal disease

Key Findings & Significance

  • Active inflammation: mural thickening >3 mm with hyperenhancement and mural stratification (target/bilaminar pattern)
  • Comb sign: engorged, comb-like mesenteric vasa recta indicating active disease
  • Fibrofatty proliferation (creeping fat) reflecting chronic disease
  • Stricture with proximal small bowel dilatation, distinguishing inflammatory from fibrotic components
  • Penetrating disease: enteroenteric or enterocutaneous fistula, phlegmon and rim-enhancing abscess

Differential Considerations

  • Ulcerative colitis and indeterminate colitis (predominantly colonic involvement)
  • Infectious enteritis (e.g. tuberculosis, Yersinia) mimicking terminal ileal Crohn disease
  • Small bowel neoplasm: adenocarcinoma, lymphoma, neuroendocrine tumour
  • Ischaemic enteritis and radiation enteritis
  • NSAID-induced enteropathy and other segmental inflammatory processes

Pearls & Pitfalls

  • Adequate luminal distension is essential; collapsed loops can mimic or mask mural thickening
  • Mural stratification with a hyperenhancing mucosa favours active inflammation over pure fibrosis
  • Low-kVp or dual-energy iodine imaging increases conspicuity of mural hyperenhancement
  • MR enterography is preferred when repeated follow-up is anticipated to limit cumulative radiation, particularly in young patients

Structured Report

  • State segments involved, length of disease and presence of skip lesions
  • Grade active inflammation (mural thickness, enhancement pattern, comb sign)
  • Describe strictures with upstream dilatation and estimate luminal calibre
  • Report penetrating complications with location and size of any abscess
  • Note extraintestinal findings (sacroiliitis, cholelithiasis, urolithiasis) and compare with priors

References

  • ACR-SAR-SPR Practice Parameter for the Performance of CT Enterography
  • Radiographics: Guglielmo FF et al. Small Bowel Crohn Disease at CT and MR Enterography
  • Society of Abdominal Radiology Crohn Disease-Focused Panel consensus recommendations
  • Bruining DH et al. Consensus Recommendations for Evaluation, Interpretation, and Utilization of CT and MR Enterography, Radiology

Educational clinical decision support only. Protocols vary by institution and equipment; always confirm with a qualified radiologist and local guidelines before clinical use.