A female adolescent with 12 hours of right lower quadrant pain, rebound tenderness, nausea and vomiting—what is the safest initial step: obtain an abdominal CT scan, give IV fluids with 24‑hour observation, or proceed directly to appendectomy?

Management of Suspected Acute Appendicitis in an Adolescent Female

Obtain a CT abdomen and pelvis with IV contrast immediately before proceeding to surgery. 1

Rationale for Imaging Before Appendectomy

Even with classic peritoneal signs, preoperative CT is essential because clinical assessment alone misdiagnoses appendicitis in 34–68% of cases. 1 The negative appendectomy rate without imaging reaches 14.7–25%, but drops dramatically to 1.7–7.7% when CT is obtained first. 1

Diagnostic Performance of CT

• CT abdomen and pelvis with IV contrast demonstrates 85.7–100% sensitivity and 94.8–100% specificity for acute appendicitis, providing highly reliable confirmation. 2, 1
• CT identifies an alternative diagnosis in 23–45% of patients presenting with right lower quadrant pain and classic symptoms, fundamentally changing management in nearly half of cases. 1
• Use IV contrast alone without oral contrast to enable rapid acquisition while maintaining excellent diagnostic accuracy. 2, 1

Critical Alternative Diagnoses Detected by CT

CT frequently reveals conditions that mimic appendicitis but require completely different management:

• Right-sided colonic diverticulitis (approximately 8% of cases) 1
• Gynecologic pathology including ovarian torsion, ruptured cysts, ectopic pregnancy, or pelvic inflammatory disease (21.6% of alternative diagnoses) 1
• Small bowel obstruction (approximately 3% of cases) 1
• Ureteral calculi 1
• Other gastrointestinal conditions (46% of alternative diagnoses) 1

Why Not Immediate Appendectomy?

Proceeding directly to surgery without imaging exposes this patient to a 14.7–25% risk of unnecessary appendectomy, with associated surgical morbidity, recovery time, and potential complications. 1 In reproductive-age women specifically, the negative appendectomy rate without CT reaches 42% compared to only 17% when CT is obtained. 3

Why Not IV Fluids and 24-Hour Observation?

This patient has high-risk features—12 hours of symptoms with rebound tenderness—that place her beyond the low-risk category where observation alone is appropriate. 4 The ACR guidelines specifically recommend imaging for intermediate and high clinical risk patients rather than observation. 2

Common Pitfalls to Avoid

• Do not assume fever is required for appendicitis—fever is absent in approximately 50% of cases. 1
• Do not rely on normal white blood cell count to exclude appendicitis—early appendicitis frequently presents with normal inflammatory markers. 1
• Do not delay imaging based on clinical improvement—appendicitis can have a waxing-waning course, and an enlarged appendix (>8.2 mm) carries >90% probability of true appendicitis regardless of symptom fluctuation. 4

Management Algorithm After CT

If CT confirms appendicitis: Proceed immediately to surgical consultation for appendectomy. 4

If CT shows perforated appendicitis with abscess: Consider percutaneous drainage followed by interval appendectomy. 4

If CT is negative but shows alternative pathology: Direct management toward the specific diagnosis identified (gynecologic referral, medical therapy for diverticulitis, etc.). 1

If CT is completely negative and clinical suspicion remains high: Consider diagnostic laparoscopy, which provides both diagnosis and therapeutic options. 1

Cost-Effectiveness

CT scanning saves an average of $1,412 per patient when accounting for avoided negative appendectomies, shorter hospital stays, and prevention of complications from delayed or incorrect diagnosis. 3