Pre-Test Preparation for CECT Abdomen

1. Fasting (NPO Status)

• Nothing by mouth for 4-6 hours before the scan (no food, no fluids except water).
• A light meal is permissible up to 4 hours prior for elective scans.
• This reduces the risk of aspiration should contrast reactions cause nausea/vomiting, and also improves bowel contrast differentiation.

2. Renal Function Assessment

• Serum creatinine and eGFR must be obtained before administering IV iodinated contrast.
• Risk of contrast-induced nephropathy (CIN) is low when eGFR >60 mL/min.
• Risk rises significantly when eGFR <60 mL/min, especially in elderly patients and diabetics.
• In patients with CKD stage 4-5 (eGFR <30 mL/min), consider alternative imaging (non-contrast CT, MRI, ultrasound) if clinically possible - per the ACR Manual on Contrast Media and Grainger & Allison's Diagnostic Radiology.
• CIN is defined as: serum creatinine rise of ≥0.3 mg/dL or ≥50% increase within 48 hours of contrast, or urine output <0.5 mL/kg/h for 6+ hours.

3. Oral Contrast Administration

• Oral contrast (dilute barium sulfate or iodinated solution) is given to opacify bowel loops.
• Standard protocol: 1 bottle (1000 mL water) 20-30 minutes before the scan (neutral agent for most non-acute indications).
• For infection/abscess workup: positive oral contrast agent given earlier (up to 2 hours before).

4. IV Access

• A large-bore IV cannula (20G or larger, preferably antecubital) is placed for contrast injection at 3-5 mL/s.
• Contrast volume: typically 70-100 mL (1 mL/kg) with a 30-40 mL saline chaser (per Radiopaedia CT abdomen protocol).

5. Hydration

• Pre- and post-scan IV hydration with normal saline is recommended for patients with eGFR <60 mL/min to reduce CIN risk.
• Per Harrison's Principles of Internal Medicine (22nd ed.): "In such patients [GFR <60, especially older diabetic subjects], appropriate screening and pre- and postscan hydration are necessary."

6. Medications to Withhold

7. Allergy & Contrast Reaction Screening

• Ask about prior contrast reactions, iodine allergy, shellfish allergy (shellfish allergy is a weak predictor but traditionally asked).
• If prior mild-moderate contrast reaction: consider premedication protocol - oral prednisolone 50 mg at 13h, 7h, and 1h before contrast, plus oral antihistamine (diphenhydramine 50 mg) 1 hour before.
• If prior severe/anaphylactic reaction: use alternative imaging if possible.

8. Pregnancy Screening

• In women of childbearing age: always ask about the possibility of pregnancy.
• Iodinated contrast crosses the placenta; use only if clinically essential.

9. Patient Positioning & Other Preparation

• Remove metal objects, jewellery, belts that could cause artefacts.
• Patient lies supine, arms elevated above the head (reduces streak artefacts and improves image quality).
• Instruct patient about breath-hold instructions (the scan requires a single breath-hold of 10-20 seconds).
• Inform the patient about the warm flushing sensation felt when contrast is injected (this is normal and expected).

Summary Checklist