Absolute Indications for CT Abdomen in Children
CT abdomen and pelvis with IV contrast is absolutely indicated in hemodynamically stable children with blunt abdominal trauma when there is clinical suspicion of intra-abdominal injury based on specific high-risk features, and in any child with suspected complicated appendicitis requiring assessment for perforation, abscess, or bowel obstruction. 1, 2
Trauma-Related Absolute Indications
Hemodynamically Stable Children with High-Risk Clinical Features
- Abdominal pain, distension, or vomiting in the setting of trauma mandates CT evaluation 1
- Abdominal wall bruising or seatbelt sign indicating significant force transmission 1, 3
- Hypoactive or absent bowel sounds suggesting peritoneal irritation 1
- Abnormal liver transaminases (AST >200 U/L) or elevated pancreatic enzymes indicating occult solid organ or pancreatic injury 4, 1
- Abnormal chest radiograph in the trauma setting, as this correlates with higher risk of intra-abdominal injury 4
Critical Caveat for Trauma
Hemodynamic instability or frank peritonitis are absolute contraindications to CT—these children require immediate surgical exploration, not imaging. 1, 2 The only exception is when FAST ultrasound can rapidly exclude intraperitoneal hemorrhage in an unstable patient who cannot be transported to CT 2.
Free Air on Plain Radiograph
Free intraperitoneal air on plain abdominal radiograph is an absolute indication for laparotomy, not CT, as it confirms hollow viscus perforation. 3 However, if free air is suspected but not clearly visible on plain films, CT can definitively identify pneumoperitoneum 3.
Appendicitis-Related Absolute Indications
Suspected Complicated Appendicitis
CT abdomen and pelvis with IV contrast is absolutely indicated when clinical examination or initial ultrasound suggests complications such as:
- Perforation with abscess formation 2
- Bowel obstruction secondary to appendicitis 2
- Periappendiceal phlegmon or mass requiring characterization 2
The broad field of view provided by CT is essential for assessing the full extent of complications, including upper abdominal collections that ultrasound cannot adequately evaluate 2.
Equivocal or Nondiagnostic Ultrasound with Persistent Clinical Concern
When ultrasound shows inflammatory findings in the right lower quadrant but the appendix is not definitively visualized, CT is indicated as appendicitis is present in 26% of these cases 2. This differs from a truly negative ultrasound (no appendix visualized, no inflammatory changes), which has high negative predictive value and does not require CT 5, 2.
Neurologically Impaired Children: A Common Pitfall
Neurologic impairment alone (GCS <8) is NOT an absolute indication for abdominal CT. 6 While neurologically impaired children have higher rates of abdominal injury (27.8% vs 17.8%), every child with actual abdominal injury on CT had specific abdominal signs 6. CT should only be performed if there are concurrent abdominal signs, abnormal mechanism, or laboratory abnormalities—not based solely on inability to examine due to altered mental status. 6
Radiation Considerations
- Use low-dose protocols (3-6 mSv instead of 11-24 mSv) when CT is indicated 2
- Contrast-enhanced CT with IV contrast is preferred over unenhanced CT as unenhanced studies have limited ability to characterize complications like perforation and abscess 2
- MRI is an equivalent alternative to CT for appendicitis evaluation when radiation avoidance is prioritized, with similar sensitivity (97%) and specificity (98%) 5, 2
What is NOT an Absolute Indication
- Low clinical risk for appendicitis (imaging not generally recommended) 2
- High clinical risk for appendicitis without complications (may proceed directly to surgery without imaging in some centers) 2
- Isolated neurologic impairment without abdominal signs 6
- Hemodynamic instability (contraindication to CT; requires immediate surgery or bedside FAST) 1, 2