Small bowel distension is mandatory for the assessment of the bowel wall in CT enterography, but some patients were sufferring inadequate small bowel distension. So, it is important to prescribe personalized regimen according to patient's personal characteristics.

CT enterography has become an important tool in the evaluation of small bowel diseases, especially in patients with inflammatory bowel diseases. Small bowel distension is mandatory for the assessment of the bowel wall. So, it is important to find clinical risk factors for inadequate small bowel distension and prescribe personalized regimen according to patient's personal characteristics to reduce patient acceptance.

Inclusion Criteria:

• patients undergoing CT enterography

Exclusion Criteria:

• patients with a history of GI surgery
• patients with known or suspected bowel obstruction or perforation
• patients with severe chronic renal failure (creatinine clearance<30 ml/min)
• patients with uncontrolled hypertension (systolic blood pressure>170 mm Hg, diastolic blood pressure>100 mm Hg)
• patients with acute upper GI bleeding
• patients with severe inflammatory bowel disease or megacolon
• patients with documented allergy to intravascular contrast agent
• patients with pregnancy or lactation
• patients hemodynamically unstable
• patients unable to give informed consent.