CT enterography (protocol)

Computed tomographic (CT) enterography is a non-invasive technique for diagnosis of small bowel disorders.

Advantages

• evaluates the entire thickness of the bowel wall
• offers information about the surrounding mesentery, the mesenteric vasculature and the perienteric fat
• useful in the assessment of the solid organs and provides global overview of the abdomen ¹

Disadvantages 

• exposure to ionizing radiation

Technique

Adequate luminal distension is necessary as collapsed bowel loops may mimic pathology. CT enterography utilizes two types of contrast:

• neutral oral contrast agents^1,3
  • these have attenuation attenuation similar to that of water e e.g. water, PEG electrolyte solution, methyl cellulose
  • intravenous contrast is used with neutral agents
  • these agents allow better assessment of mucosal enhancement, mural thickness as well as mesenteric vasculature, this is important especially in the evaluation of Crohn's disease ²
• positive contrast agents ³
  • such as a dilute dilute (1%) barium solutions
  • they are not routinely used in CT enterogrpahyenterography
  • pathologic mural enhancement and intestinal hemorrhage are obscured by positive contrast agents
  • mainly used to detect lower grades of small bowel obstruction and internal fistula

Procedure 

Actual procedure will vary depending on institutional protocol/guidelines but below is a typical description ^{1, 2}:

1. Abstain from all food and drink 4-6 hours before the exam.
2. Patients drink about 1.5- 2 L of oral contrast over 40-60 minutes.
3. Administration of intravenous contrast injection at a rate 4 ml/sec.
4. CT scanning is ideally performed on a multi-detector computed tomography (MDCT) scanner about 45-65 seconds after contrast material injection in a single (venous) phase or dual (arterial & venous) phases for the evaluation of mesenteric vasculature or GI tract bleeding.
5. Data interpretation with the use of axial and coronal reformatted images for proper evaluation.

Findings

• inflammatory bowel disease and its complications e.g. Crohn's disease or ulcerative colitis
• small bowel tumors, including benign tumors (e.g. hamartomatous or hyperplastic polyps) or malignant tumors (e.g. adenocarcinoma, carcinoid, lymphoma and gastrointestinal stromal tumors)
• mesenteric ischemia and gastrointestinal tract bleeding
• Coeliac disease ^{1, 2}

See also

• CT enteroclysis
• MR enterography
• MR enteroclysis