Best investigation for diagnosis of ampullary gall stone with obstructive jaundice is:
**Core Concept**
The diagnosis of ampullary gallstone with obstructive jaundice requires a precise imaging modality that can visualize the biliary system and the gallbladder. The ampulla of Vater, where the bile and pancreatic ducts merge, is a critical area to be evaluated in cases of obstructive jaundice.
**Why the Correct Answer is Right**
Endoscopic retrograde cholangiopancreatography (ERCP) is the gold standard investigation for diagnosing ampullary gallstones causing obstructive jaundice. ERCP allows for direct visualization of the biliary and pancreatic ducts, enabling the identification of ampullary gallstones. Additionally, ERCP enables therapeutic interventions such as sphincterotomy and stone extraction. The combination of imaging and therapeutic capabilities makes ERCP an ideal choice for managing ampullary gallstones.
**Why Each Wrong Option is Incorrect**
**Option A:** Ultrasound is useful for detecting gallstones but may not accurately diagnose ampullary gallstones or evaluate the biliary system in detail.
**Option B:** CT scan can detect gallstones and evaluate the biliary system, but it may not provide the detailed imaging necessary for diagnosing ampullary gallstones.
**Option C:** MRCP (Magnetic Resonance Cholangiopancreatography) is a non-invasive imaging modality that can evaluate the biliary system, but it may not provide the same level of detail as ERCP for diagnosing ampullary gallstones.
**Clinical Pearl / High-Yield Fact**
ERCP is a valuable diagnostic and therapeutic tool for managing biliary disorders, including ampullary gallstones. Its ability to provide real-time imaging and allow for therapeutic interventions makes it a crucial investigation in the management of obstructive jaundice.
**Correct Answer:** C. ERCP