CT Abdomen and Pelvis is the Next Step
For a patient presenting with 12 hours of right lower quadrant pain, tenderness, and rebound tenderness, obtain CT abdomen and pelvis with IV contrast immediately before proceeding to surgery. 1, 2
Why Imaging Before Surgery is Critical
The negative appendectomy rate based on clinical assessment alone reaches 25%, which is unacceptably high and exposes patients to unnecessary surgical complications. 1 Even with classic clinical presentation (right lower quadrant pain, tenderness, and rebound), preoperative CT reduces the negative appendectomy rate from 14.7-25% to 1.7-7.7%. 2
Clinical determination of appendicitis is notoriously poor, and rebound tenderness alone—while highly sensitive (91%)—has a positive predictive value of only 39%. 1, 3 This means that even with classic peritoneal signs, the majority of patients do not have appendicitis.
Diagnostic Performance of CT
CT abdomen and pelvis with IV contrast demonstrates:
- Sensitivity: 85.7-100% 1, 2
- Specificity: 94.8-100% 1, 2
- Identifies alternative diagnoses in 23-45% of patients with right lower quadrant pain and classic symptoms 2
The most common alternative diagnoses detected by CT include right colonic diverticulitis (8%), gynecologic pathology (21.6%), gastrointestinal conditions (46%), ureteral stones, and intestinal obstruction. 2
Why Not Proceed Directly to Surgery?
While this patient has classic findings, fever is absent in approximately 50% of appendicitis cases, so the absence of fever mentioned in typical presentations should not guide decision-making. 2 More importantly, surgeon's macroscopic judgment of early appendicitis is inaccurate and highly variable, with 19-40% of visually normal appendices showing pathological abnormalities on histology. 1
Why Not Observation or Antibiotics Alone?
- 24-hour observation without imaging is not appropriate for patients with established peritoneal signs (rebound tenderness), as this represents intermediate-to-high risk presentation requiring definitive diagnosis. 2
- Antibiotics without diagnosis confirmation would be inappropriate as you haven't established whether this is appendicitis or one of the many alternative diagnoses that require different management. 2
- IV fluids and observation delay definitive diagnosis in a patient with 12 hours of symptoms and peritoneal signs, risking progression to perforation. 1
Recommended CT Protocol
Order CT abdomen and pelvis with IV contrast without enteral contrast for: 2
- Rapid acquisition without delays from oral contrast administration
- Excellent sensitivity and specificity
- Detection of alternative diagnoses
- Assessment for perforation and abscess formation
Look for appendiceal diameter >8.2 mm, periappendiceal fat stranding, absence of intraluminal gas, and presence of appendicoliths. 2
Management After CT
- If appendicitis confirmed: Proceed to surgical consultation and appendectomy 2
- If alternative diagnosis identified: Manage accordingly (23-45% of cases) 2
- If negative CT: Consider safe discharge with mandatory 24-hour follow-up and clear return precautions 2
Critical Pitfall to Avoid
Do not proceed directly to open appendectomy based on clinical findings alone. The combination of imaging utilization does not increase perforation rates from diagnostic delays, but significantly reduces unnecessary surgeries and their attendant complications. 1