A 32-year-old man presents with acute onset of right lower abdominal pain, fever (38.5°C), and localized tenderness over McBurney's point. Clinical examination suggests acute appendicitis. Which investigation is the gold standard for confirming the diagnosis before surgical intervention?

## Investigation of Choice for Acute Appendicitis **Key Point:** High-resolution contrast-enhanced CT (HRCT) abdomen and pelvis is the gold standard investigation for confirming acute appendicitis in adults with diagnostic sensitivity and specificity both >95%. ### Why HRCT is Superior **High-Yield:** HRCT can visualize: 1. Appendiceal wall thickening (>2 mm) 2. Appendiceal distension (>6 mm diameter) 3. Periappendiceal fat stranding and fluid collection 4. Complications: perforation, abscess formation 5. Differential diagnoses (ovarian pathology, diverticulitis, mesenteric adenitis) **Clinical Pearl:** HRCT has largely replaced clinical scoring systems (Alvarado score) and ultrasound in developed healthcare settings due to superior accuracy and ability to detect complications that alter surgical approach. ### Comparison of Imaging Modalities | Investigation | Sensitivity | Specificity | Advantages | Limitations | |---|---|---|---|---| | **HRCT** | 95–98% | 95–98% | Gold standard; detects complications; rules out mimics | Radiation exposure; cost | | **Ultrasound** | 85–90% | 90–95% | No radiation; operator-dependent; good in lean patients | Limited in obese patients; cannot assess perforation reliably | | **MRI** | 90–95% | 95% | No radiation; excellent soft tissue; safe in pregnancy | Expensive; time-consuming; not first-line | | **Plain X-ray** | 50–60% | 70% | Rapid; no radiation dose | Poor sensitivity; non-specific findings | **Tip:** In pregnancy, MRI is preferred over CT to avoid fetal radiation exposure. In children with equivocal clinical signs, ultrasound is often the first-line imaging. [cite:Robbins 10e Ch 2]