A 28-year-old woman presents with 18 hours of periumbilical pain that has migrated to the right lower quadrant, accompanied by anorexia and low-grade fever (38.2°C). On examination, she has tenderness at McBurney's point with positive Rovsing's sign. Her WBC is 12,500/μL with left shift. What is the investigation of choice to confirm the diagnosis?

Explanation

## Investigation of Choice in Acute Appendicitis **Key Point:** Contrast-enhanced CT (CECT) abdomen and pelvis is the gold standard imaging modality for confirming acute appendicitis when clinical diagnosis is uncertain or when complications are suspected. ### Why CECT is Superior **High-Yield:** CECT has a sensitivity of 94–98% and specificity of 95–98% for acute appendicitis, making it the most accurate imaging study. It reliably visualizes: - Dilated, fluid-filled appendix (>6 mm diameter) - Appendiceal wall enhancement and thickening - Periappendiceal fat stranding - Complications (perforation, abscess, peritonitis) ### Comparison of Imaging Modalities | Investigation | Sensitivity | Specificity | Advantages | Limitations | |---|---|---|---|---| | **CECT** | 94–98% | 95–98% | Gold standard; detects complications; excellent for atypical presentations | Radiation exposure; contrast allergy risk | | **Ultrasound** | 86–88% | 95–97% | No radiation; first-line in pregnancy/children; cost-effective | Operator-dependent; limited by bowel gas; poor in obese patients | | **Plain X-ray** | 5–15% | 90% | Readily available; no radiation risk | Non-specific; only shows complications (free air, obstruction) | | **MRI** | 90–95% | 95–97% | Excellent for pregnancy; no radiation | Expensive; time-consuming; limited availability | **Clinical Pearl:** In this patient with classic clinical presentation (migration of pain, RLQ tenderness, Rovsing's sign positive, leukocytosis with left shift), the diagnosis is highly likely clinically. However, CECT is chosen because: 1. It confirms diagnosis objectively before surgery 2. It excludes mimics (Crohn's disease, gynecologic pathology, mesenteric adenitis) 3. It detects perforation, abscess, or peritonitis that would alter surgical approach **Mnemonic: CECT GOLD** — **C**onfirms diagnosis, **E**xcels at complications, **C**ost-effective for definitive imaging, **T**rust-worthy accuracy; **G**old standard, **O**ptimal sensitivity/specificity, **L**arge field of view, **D**etects mimics. ### Clinical Context In this patient: - Clinical suspicion is high (classic presentation) - No contraindications to CT (not pregnant, no renal failure mentioned) - CECT will confirm appendicitis and rule out perforation before operative planning