**Question:** A 26-year-old male presents with acute right lower quadrant pain in abdomen. Suspecting appendicitis, a USG is done but it is equivocal. Next investigation would be:

A. Abdominal X-ray
B. Serum Biochemistry
C. Ultrasound with Doppler study
D. Computed Tomography (CT) Scan

**Correct Answer:** D. Computed Tomography (CT) Scan

**Core Concept:**

Appendicitis is a common abdominal emergency characterized by inflammation of the appendix, which typically presents with acute onset right lower quadrant pain. Ultrasound (USG) is the initial imaging modality of choice for suspected appendicitis. However, equivocal results may occur in cases with thickened appendiceal wall, causing difficulty in distinguishing appendicitis from other causes of right lower quadrant pain. In such cases, advanced imaging modalities are required for accurate diagnosis.

**Why the Correct Answer is Right:**

Given the equivocal ultrasound result, the next appropriate investigation is a Computed Tomography (CT) Scan. A CT scan is a highly sensitive and specific diagnostic tool for evaluating appendicitis and can provide detailed information on the appendix wall thickness, surrounding inflammation, and the presence of collection or abscess. This increases the accuracy of diagnosis and helps in guiding appropriate management, as contrast-enhanced CT scan can accurately depict the vascularity of the appendix, which is helpful in distinguishing appendicitis from other causes of right lower quadrant pain like renal colic or renal calculi.

**Why Other Options are Incorrect:**

A. Abdominal X-ray: While X-rays can detect appendiceal perforation, it is less sensitive in detecting appendicitis in its early stages. Appendicitis may be difficult to visualize due to nonspecific findings and poor soft tissue resolution.

B. Serum Biochemistry: Biochemistry tests are helpful in assessing organ function and general health status but do not directly aid in diagnosing appendicitis. Biochemical parameters are not specific to appendicitis and can be abnormal in various other conditions.

C. Ultrasound with Doppler study: Although Doppler ultrasound is more sensitive than conventional ultrasound, it is not necessary in this scenario since the initial ultrasound (USG) result is equivocal. Performing an additional Doppler study would not significantly improve the diagnostic accuracy beyond the initial ultrasound.

**Clinical Pearl:** In cases of equivocal ultrasound results, consider using a contrast-enhanced CT scan as the next diagnostic step for accurate appendicitis diagnosis and guiding management. If appendicitis is suspected, a contrast-enhanced CT scan can provide valuable information regarding the appendix wall thickness, surrounding inflammation, and the presence of collection or abscess. This increases the diagnostic accuracy and helps in determining the appropriate management plan, as contrast-enhanced CT scans can depict the vascularity of the appendix, which is helpful in distinguishing appendicitis from other causes of right lower quadrant pain like renal colic or renal calculi.