What is the next step for a patient presenting to the Emergency Room (ER) with 12 hours of right lower abdominal pain, tenderness, and rebound tenderness?

CT Abdomen and Pelvis with IV Contrast is the Next Step

For a patient presenting with 12 hours of right lower quadrant pain, tenderness, and rebound tenderness, proceed immediately to CT abdomen and pelvis with IV contrast to confirm appendicitis and exclude alternative diagnoses before surgical intervention. 1, 2

Why Imaging is Essential Before Surgery

The clinical diagnosis of appendicitis is notoriously unreliable, with negative appendectomy rates reaching 25% when based on clinical assessment alone. 1, 2 While this patient has classic peritoneal signs (rebound tenderness), these findings alone have a positive predictive value of only 39%, meaning 61% of patients with rebound tenderness do not have appendicitis. 3

CT imaging provides 85.7-100% sensitivity and 94.8-100% specificity for diagnosing appendicitis, dramatically reducing unnecessary surgeries while identifying alternative diagnoses in 23-45% of patients presenting with right lower quadrant pain. 1, 2

Why Other Options Are Inappropriate

Open Appendectomy Without Imaging

• Proceeding directly to surgery risks a negative appendectomy rate of 16.7% compared to 8.7% when CT is performed preoperatively. 4
• The American College of Radiology explicitly states that imaging remains the diagnostic mainstay for suspected appendicitis, as clinical determination alone is inadequate. 1
• Even with classic findings (pain, tenderness, rebound), 15.6% of patients with these symptoms but no fever or inflammatory markers still require imaging confirmation. 5

Plain Abdominal X-ray

• Plain films have no role in diagnosing acute appendicitis and would only delay definitive imaging. 1, 2
• The ACR guidelines do not recommend plain radiography for suspected appendicitis evaluation. 1

IV Fluids and 24-Hour Observation

• This approach is only appropriate for low-risk patients who can be safely discharged with return precautions, not for patients with established peritoneal signs. 2
• A patient with 12 hours of pain and rebound tenderness has already progressed beyond the observation window—delays increase perforation risk without improving diagnostic accuracy. 1
• The World Journal of Emergency Surgery recommends serial examinations every 6-12 hours during observation, but this patient already demonstrates progression with rebound tenderness requiring immediate diagnostic clarification. 2

The Diagnostic Algorithm

1. Obtain CT abdomen/pelvis with IV contrast immediately for patients with right lower quadrant pain and peritoneal signs. 1, 2

2. If CT confirms appendicitis: Proceed to appendectomy (laparoscopic preferred over open in most cases). 1

3. If CT shows alternative diagnosis: Manage accordingly (diverticulitis, ovarian pathology, bowel obstruction, etc.). 2

4. If CT is negative or equivocal: Arrange mandatory 24-hour follow-up with clear return precautions for worsening symptoms. 2

Critical Pitfalls to Avoid

• Do not rely on absence of fever to exclude appendicitis—fever is absent in approximately 50% of appendicitis cases. 2, 5
• Do not assume normal white blood cell count rules out appendicitis—15.6% of confirmed appendicitis cases present without leukocytosis or fever. 5
• Do not delay imaging if peritoneal signs are present—rebound tenderness indicates peritoneal irritation requiring urgent diagnostic clarification, not observation. 2, 3
• Do not proceed to surgery without imaging in stable patients—preoperative CT reduces negative appendectomy rates by nearly 50%. 4

Why CT Over Ultrasound in Adults

While ultrasound is first-line in pediatric patients to avoid radiation, CT is superior in adults due to body habitus and the need for comprehensive evaluation of alternative diagnoses. 1, 2 Ultrasound has 76-87% sensitivity compared to CT's 90-94% sensitivity, and CT better identifies non-appendiceal pathology requiring different management. 6