A 32-year-old woman presents with acute onset of right lower abdominal pain, fever (38.5°C), and localized tenderness over McBurney's point. Clinical examination reveals rebound tenderness and guarding. Which investigation is most appropriate to confirm acute appendicitis and rule out other differential diagnoses?

Explanation

## Investigation of Choice for Acute Appendicitis **Key Point:** High-resolution contrast-enhanced CT (HRCT) abdomen and pelvis is the gold standard imaging modality for confirming acute appendicitis with highest sensitivity and specificity. ### Why CT is Superior | Feature | CT | Ultrasound | Plain X-ray | Diagnostic Laparoscopy | |---------|----|-----------|-----------|-----------| | Sensitivity | 94–98% | 75–90% | ~40% | 100% (surgical) | | Specificity | 95–98% | 85–95% | ~50% | 100% (surgical) | | Visualization of appendix | Excellent | Variable (operator-dependent) | Poor | Direct visualization | | Detection of complications (perforation, abscess) | Excellent | Moderate | Poor | Excellent | | Radiation exposure | Yes | No | Yes | None | | Availability & speed | High | High | High | Requires OR | **High-Yield:** CT can visualize: - Dilated, non-compressible appendix (>6 mm) - Appendiceal wall enhancement - Periappendiceal fat stranding - Fluid collections and abscess formation - Alternative diagnoses (diverticulitis, ovarian pathology, mesenteric adenitis) ### Clinical Pearl **Key Point:** In acute appendicitis, CT findings of appendiceal diameter >6 mm, wall enhancement, and periappendiceal inflammatory changes are highly specific. CT also identifies complications like perforation (free air, abscess) that alter surgical urgency. ### Why Other Options Are Suboptimal 1. **Ultrasound** — Operator-dependent, limited by bowel gas, cannot reliably exclude appendicitis in all patients; acceptable alternative in pregnancy or pediatrics where radiation is avoided. 2. **Plain X-ray** — Non-specific; shows only indirect signs (free air if perforated); poor sensitivity and specificity; cannot visualize appendix directly. 3. **Diagnostic laparoscopy** — Invasive surgical procedure; reserved for cases where imaging is inconclusive or when immediate surgical intervention is planned; not a diagnostic tool in the modern era given CT availability. [cite:Robbins 10e Ch 2]