When is it appropriate to order an abdominal computed tomography (CT) scan in a child?

When to Order CT Abdomen in a Child

CT abdomen should be reserved for specific high-risk scenarios in children: suspected complicated appendicitis (perforation, abscess, obstruction), equivocal ultrasound with persistent high clinical suspicion, hemodynamically stable abdominal trauma with concerning clinical features, or suspected intra-abdominal abscess when ultrasound is inconclusive. 1, 2

Clinical Risk Stratification Framework

Low Clinical Risk Patients

• Do not order imaging for children with low clinical suspicion for appendicitis (Pediatric Appendicitis Score <4). 1, 3
• Instead, evaluate for alternative causes such as constipation, gastroenteritis, or respiratory infections. 3
• Plain radiographs may identify alternative pathology like constipation or lower-lobe pneumonia in this group. 4

Intermediate Clinical Risk Patients

• Start with ultrasound of the right lower quadrant as the first-line imaging modality (sensitivity 76-86%, specificity 95-97%). 1, 3
• Ultrasound avoids radiation exposure and can identify alternative diagnoses including ovarian pathology in females. 3
• Proceed to CT abdomen/pelvis with IV contrast only if ultrasound is equivocal or nondiagnostic and clinical suspicion remains high. 1, 3
• MRI without IV contrast is an equivalent alternative to CT when available, with sensitivity 86-94% and specificity 94%, avoiding radiation exposure. 1, 3

High Clinical Risk Patients

• Children with high clinical suspicion (score >7) may proceed directly to surgical consultation without imaging. 1
• When imaging is performed in this group, CT abdomen/pelvis with IV contrast, MRI, or ultrasound may be appropriate depending on institutional protocols. 1

Specific Indications for CT Abdomen

Suspected Complicated Appendicitis

• CT with IV contrast is usually appropriate when clinical examination or initial imaging suggests complications including: 1, 2
  • Perforation with abscess formation
  • Bowel obstruction
  • Periappendiceal phlegmon or mass requiring characterization
• Complicated appendicitis occurs in approximately 30% of pediatric patients and has significant implications for management. 1

Abdominal Trauma

• CT abdomen/pelvis with IV contrast (including delayed urographic phase) is the gold standard for hemodynamically stable children with suspected intra-abdominal injury. 2
• High-risk clinical features warranting CT include: 2
  • Abdominal pain, distension, or vomiting
  • Abdominal wall bruising
  • Hypoactive or absent bowel sounds
  • Abnormal liver transaminases (AST/ALT >80 U/L) or elevated pancreatic enzymes
• Do not obtain CT in hemodynamically unstable children or those with frank peritonitis—these require immediate surgical exploration. 2

Suspected Intra-Abdominal Abscess

• In children, ultrasound is the preferred initial imaging modality for suspected intra-abdominal abscess. 1
• CT with IV contrast is suggested when ultrasound is unavailable, inconclusive, or technically limited. 1
• MRI is a reasonable alternative when available, though sedation may be required for young children. 1

Suspected Child Abuse

• CT or MRI abdomen should be obtained in children with suspected abuse who have signs or history of abdominal injury or unexplained elevated liver enzymes (AST or ALT >80 U/L). 1

Critical Radiation Safety Principles

ALARA Principle

• Pediatric patients are at inherently higher risk from radiation exposure due to increased organ sensitivity and longer life expectancy for potential cancer development. 1, 5, 6
• Always use the lowest radiation dose reasonably achievable when CT is indicated, with low-dose protocols (3-6 mSv instead of 11-24 mSv) preferred. 2, 5
• Limit the region of coverage and adjust CT settings based on indication, region imaged, and size of the child. 5, 6

Contrast Administration

• IV contrast is usually appropriate whenever CT is obtained for appendicitis or trauma, as it improves visualization of bowel wall abnormalities, abscess walls, and complications. 1, 2
• CT without IV contrast has limited ability to characterize complications like perforation and abscess. 2

Common Pitfalls to Avoid

• Never use CT as first-line imaging—ultrasound should always be attempted first in pediatric patients to avoid unnecessary radiation exposure. 1, 3
• Do not obtain plain radiographs as the primary imaging modality for appendicitis, as they are neither sensitive nor specific. 3
• Do not assume a negative ultrasound rules out all pathology—if clinical suspicion remains high despite negative ultrasound, proceed to CT or MRI rather than discharging the patient. 3
• Do not order CT routinely for children with nonspecific abdominal pain and low clinical risk—seek alternative causes instead. 3, 4
• Recognize atypical presentations in children under 5 years, who have significantly higher perforation rates due to delayed diagnosis from atypical symptoms. 4

Alternative Imaging Strategies

• Ultrasound is operator-dependent and may yield equivocal results, but remains the preferred initial modality in most pediatric abdominal scenarios. 1, 3
• MRI provides comparable diagnostic accuracy to CT without radiation exposure, though availability may be limited and sedation may be required for young children. 1
• For neonates specifically, when diagnostic yield is similar between CT and MRI but sedation is required for MRI, CT likely has the higher benefit-to-risk ratio despite radiation concerns. 7