What is the next step in management for a 5-year-old child with abdominal pain and vomiting, who underwent abdominal x-ray and ultrasound (US) that failed to visualize the appendix?

Next Step: CT Abdomen and Pelvis with IV Contrast

When ultrasound fails to visualize the appendix in a 5-year-old with suspected appendicitis, proceed directly to CT abdomen and pelvis with IV contrast as the next imaging study. 1

Understanding Non-Visualization on Ultrasound

The critical distinction here is whether the non-visualized appendix represents a truly negative study or an equivocal one:

• Simple non-visualization without inflammatory findings in the right lower quadrant has a high negative predictive value (93%) and typically does not require further imaging unless clinical suspicion remains high 1, 2, 3

• Non-visualization WITH inflammatory findings (periappendiceal fluid, fat stranding, or RLQ inflammatory changes) is considered equivocal, and 26% of these patients actually have appendicitis 1, 2

Since your case doesn't specify whether inflammatory findings were present, and given the persistent symptoms (abdominal pain and vomiting), further evaluation is warranted.

Recommended Next Step: CT Imaging

CT abdomen and pelvis with IV contrast is the most accurate next diagnostic modality following non-diagnostic ultrasound in children:

• Achieves 91% sensitivity and 98% specificity for appendicitis after equivocal ultrasound 1, 2
• Maintains high diagnostic accuracy (94% sensitivity, 95% specificity) as a secondary imaging modality 1
• Provides broad anatomic coverage to identify alternative diagnoses (occurring in 7-25% of cases) 1
• Has similar negative predictive value whether the appendix is visualized or not 1

Technical Considerations for CT:

• IV contrast alone is sufficient—oral and rectal contrast do not increase accuracy and may cause additional vomiting 1
• Focused CT from L2/L3 to pubic symphysis is adequate for diagnosis and reduces radiation exposure 1
• Non-contrast CT has lower sensitivity and may miss complicated appendicitis (perforation, abscess) 1

Alternative Approach: MRI

MRI abdomen and pelvis is an excellent radiation-free alternative, particularly valuable in pediatric patients:

• Demonstrates 94% sensitivity and 94% specificity with IV contrast 1
• Unenhanced MRI still achieves 86% sensitivity and 94% specificity 1
• Provides similar accuracy to CT for detecting perforation 1
• Should be strongly considered if available and if institutional expertise exists 1

Clinical Reassessment Option

Repeat clinical examination can be considered first if the child's condition is stable and clinical suspicion is not high:

• Successfully rules out appendicitis in 59% of patients with initially equivocal ultrasound 1, 2
• Avoids radiation exposure in cases that resolve spontaneously 1
• Requires close observation and ability to return for urgent re-evaluation 1

However, this approach carries risk of delayed diagnosis and should only be pursued with:

• Low-to-intermediate clinical risk scoring 1
• Reliable follow-up within 24 hours 1, 3
• Clear return precautions for worsening symptoms 1

Critical Pitfalls to Avoid

Do not repeat ultrasound as the immediate next step unless:

• The initial study was technically limited 1
• A more experienced sonographer is available 1
• You're specifically evaluating a peri-menarchal girl for gynecologic pathology 1

Repeat ultrasound only makes a diagnosis in 55% of persistent cases, which is inferior to CT's performance 1, 2

Do not obtain plain abdominal radiographs—they have limited sensitivity and specificity for appendicitis and are unlikely to change management after non-diagnostic ultrasound 1

Do not discharge without imaging or close follow-up if clinical suspicion persists, as false-negative ultrasound carries measurable risk 1

Special Consideration: Complicated Appendicitis

If there are clinical signs suggesting perforation (prolonged symptoms >48 hours, high fever, peritonitis):

• CT with IV contrast is superior to ultrasound for detecting perforation, abscess, and bowel obstruction 1
• Ultrasound has notably low sensitivity for perforated appendicitis 1
• Full abdomen/pelvis coverage (not focused RLQ) is needed to assess for distant complications 1

Practical Algorithm

1. Assess clinical risk using history, exam, and labs (WBC, CRP) 1, 4
2. If high clinical suspicion persists: Proceed to CT abdomen/pelvis with IV contrast 1, 2
3. If low-intermediate suspicion and stable: Consider 4-6 hour clinical reassessment first 1, 2
4. If MRI readily available: Use MRI instead of CT to avoid radiation 1
5. Ensure 24-hour follow-up regardless of imaging results due to false-negative risk 1, 3