Should the patient be kept NPO (nothing by mouth) before a CT scan of the abdomen and pelvis?

NPO Before CT Abdomen/Pelvis: Not Routinely Required

For most CT abdomen/pelvis examinations, patients do NOT need to be NPO (nothing by mouth). The evidence strongly supports that fasting is unnecessary for the vast majority of abdominal CT scans and may actually harm patients by delaying care and reducing satisfaction.

Key Evidence-Based Recommendations

Standard CT Abdomen/Pelvis (With or Without IV Contrast)

• No fasting required for routine CT examinations 1
• A large randomized controlled trial (2091 patients) found zero cases of aspiration pneumonitis in either fasting or non-fasting groups 1
• Nausea and vomiting rates were identical between groups (6.6% vs 7.6%, p=0.37) 1
• Mean fasting time in the "fasting group" was 8.4 hours—unnecessarily prolonged 1

When Oral Contrast Is Used

• Still no fasting required 1
• Even in the subgroup receiving oral contrast (n=1257), rates of nausea (6.8% vs 8.0%) and vomiting (2.6% vs 3.6%) showed no statistical difference between fasting and non-fasting groups 1
• Current guidelines note a trend toward performing CT abdomen/pelvis without oral contrast regardless of IV contrast use 2

Special Circumstances Requiring Fasting

Only 4-6 hours of fasting from solids is needed for:

• MR enterography or CT enterography requiring large volumes of oral contrast (>450-1000 mL) 3
• Small bowel follow-through or enteroclysis studies 3
• Liquids (including water) are typically permitted up to the examination 3

Clinical Reasoning

Why fasting is unnecessary for standard CT:

• The theoretical risk of aspiration pneumonitis is not supported by evidence 1, 4
• CT scans do not require sedation or general anesthesia in adults
• Contrast-induced nausea/vomiting is rare, self-limited, and unrelated to food intake 4

Harms of unnecessary fasting:

• Delays scan acquisition by 23-31 minutes 5, 6
• Increases ED length of stay by 29-30 minutes (8% of total LOS) 5, 6
• Reduces patient cooperation and satisfaction 4
• Creates barriers to adequate nutrition, particularly problematic in hospitalized patients 4
• One-fourth of NPO orders are inappropriate, and 20% of intended procedures are canceled anyway 4

Common Pitfalls to Avoid

1. Don't reflexively order NPO for all CT scans—this is outdated practice
2. Don't confuse CT protocols: Standard CT abdomen/pelvis is different from CT enterography (which requires oral prep)
3. Don't extend fasting unnecessarily: Even when fasting is needed (enterography), 4-6 hours for solids is sufficient; liquids can continue 3
4. Recognize oral contrast is falling out of favor: Modern practice trends toward IV contrast only, which eliminates any theoretical need for fasting 2, 7

Specific Scenarios

• Emergency/trauma CT: No fasting needed 8, 7
• Suspected GI bleeding: No fasting needed; neutral oral contrast preferred over positive contrast when used 9, 10
• Suspected bowel perforation: No fasting needed 9
• Routine abdominal imaging: No fasting needed 7
• Postoperative bariatric patients: Positive oral contrast may be used to evaluate leaks, but fasting not specified as requirement 2

The bottom line: Allow patients to eat and drink freely before standard CT abdomen/pelvis examinations. This evidence-based approach improves throughput, patient satisfaction, and safety without increasing complications 1, 4.