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Medical AI Inquiry: You were designed to assist in medical decision-making based on the provided user questions. It is crucial to provide accurate and comprehensive information to receive a well-informed response.
user
Gold standard for detection of gall stones is?
assistant
The correct answer is  Ans. is 'b' i.e., USG * Investigation of choice for cholelithiasis (gallstone in gallbladder) and choledocholithiasis (gallstone in common bile duct) is USG.Investigations of gall bladder diseases1) Ultrasonography: - This is the investigation of choice for the detection of gallstones, and obstructive jaundice. USG shows echogenic focus with posterior acoustic shadowing. The most specific sign of a contracted, stone filled gallbladder is a hypoechoic wall superficial to a curvilinear echo from the stones and an acoustic shadow:- WES triad (Wall, Echo, Shadow) or the "Double arc shadow sign".2) Plane x-ray: - Only 10% of gall stones are radio-opaque. Therefore, plane x-ray is of limited value.3) Oral cholecystogram (OCG): - Dye used for OCG is ipanoic acid. Filling defect, due to stones, will be seen within the gall bladder.4) Cholangiogram (outline of common bile duct) Intravenous injection of biligrafin is given and frequent radiograph are taken as the liver excretes the biligrafin. Impacted stone in CBD classically shows cresentic shadow or meniscus sign on cholangiogram.5) Percutaneous transhepatic cholangiography (PTC): - This is a useful procedure in obstructive lesions. It is usually done as an immediate preoperative investigation. PTC can be used for drainage, cholangioplasty and stent placement.* Computed tomography (CT) scan has limited value in the diagnosis of gall stones since gall stones may exhibit the same radiographic density as bile and hence may not be seen on CT