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?

Question

Accepted Answer

B. High-resolution contrast-enhanced CT abdomen and pelvis. ## 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]

Answer

A. Plain abdominal X-ray

Answer

C. Diagnostic laparoscopy

Answer

D. Abdominal ultrasound

Explanation

Investigation of Choice for Acute Appendicitis

Why CT is Superior

Clinical Pearl

Why Other Options Are Suboptimal

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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