Most Sensitive Investigation for Acute Appendicitis?

**Core Concept**
The diagnosis of acute appendicitis often requires a combination of clinical evaluation and radiological investigations. The most sensitive investigation is crucial in identifying the condition and guiding timely surgical intervention.

**Why the Correct Answer is Right**
The most sensitive investigation for acute appendicitis is the **Computed Tomography (CT) scan** of the abdomen. A CT scan provides detailed images of the abdominal organs, including the appendix, and can detect inflammation, perforation, or abscess formation. The CT scan's high sensitivity (95-98%) and specificity (95-98%) make it an ideal tool for diagnosing acute appendicitis, especially in cases where the diagnosis is unclear.

**Why Each Wrong Option is Incorrect**
**Option A:** Ultrasonography is less sensitive (80-90%) compared to CT scans, especially in adults with a body mass index (BMI) > 30.

**Option B:** Magnetic Resonance Imaging (MRI) is not commonly used for diagnosing acute appendicitis due to its high cost, limited availability, and longer examination time.

**Option C:** Plain abdominal X-rays are not sensitive for acute appendicitis and are often used as a preliminary investigation to rule out other causes of abdominal pain.

**Clinical Pearl / High-Yield Fact**
Remember that the diagnosis of acute appendicitis requires a high index of suspicion, and a combination of clinical evaluation, laboratory tests (e.g., white blood cell count), and radiological investigations is essential for an accurate diagnosis.

**Correct Answer:** C.