**Question:** The initial investigation of choice for a post cholecystectomy biliary stricture is:

A. Ultrasound
B. ERCP
C. MRCP
D. CECT

**Correct Answer:** D. CECT

**Core Concept:**
Post-cholecystectomy biliary stricture is a complication that can occur after a gallbladder surgery (cholecystectomy), where there is scarring or narrowing of the bile ducts. The primary investigations aimed at detecting this complication are imaging modalities that can visualize the biliary system.

**Why the Correct Answer is Right:**
CECT (Computed Tomography with Contrast) is the correct answer because it provides high-resolution images of the biliary system, allowing for the detection of biliary strictures and their characteristics. CECT can demonstrate the stricture's location, length, and degree of stenosis.

**Why Each Wrong Option is Incorrect:**
A. Ultrasound: While ultrasound is a non-invasive and readily available imaging modality, it has limited sensitivity in detecting biliary strictures. It is less accurate compared to CECT and MRCP (Magnetic Resonance Cholangiopancreatography) in detecting post-cholecystectomy biliary strictures.

B. ERCP (Endoscopic Retrograde Cholangiopancreatography): ERCP is a procedure, not an investigation. It is an invasive procedure used for diagnosis and treatment of biliary disorders, including biliary strictures. Its role is primarily in therapeutic interventions, not initial diagnosis.

C. MRCP: Magnetic Resonance Cholangiopancreatography is a non-invasive imaging modality that uses magnetic resonance to visualize the biliary and pancreatic ducts. However, its sensitivity in detecting post-cholecystectomy biliary strictures is lower compared to CECT and is less readily available.

**Clinical Pearl:**

CECT is an essential tool in the initial investigation of patients with suspected post-cholecystectomy biliary strictures as it provides high-resolution images of the biliary system, allowing for precise diagnosis and management planning. In cases where CECT is not feasible or available, MRCP can be considered due to its high spatial resolution and detailed visualization of the biliary tree. However, the choice of imaging modality should be based on the availability and expertise of the radiology department.