10. Investigation of choice for Gall stones?
Ans. B. Ultrasonography. (Harrison's Medicine, 18th/Ch. 311)The plain abdominal film may detect gallstones containing sufficient calcium to be radiopaque (10-15% of cholesterol and 50% of pigment stones). Plain radiography may also be of use in the diagnosis of emphysematous cholecystitis, porcelainUltrasonography of the gallbladder is very accurate in the identification of cholelithiasis and has replaced oral cholecystography. Stones as small as 1.5 mm in diameter may be confidently identified provided that firm criteria are used .Role of Ultrasound in Biliary System:# Ultrasound is most important modality in evaluating GB pathologies. It is investigation of choice for diagnosis of:- Gall stones (Procedure of choice for detection of stones)- GB polyp- Mucocele- Empyema of GB- Acute cholecystitis (initial/screening)- Adenomyomatosis of GB ("Comet- tail" artefacts)- Cholesterosis (Strawberry GB)- Early Carcinoma GB.# CT may be better than US in following GB pathologies:- Porcelain GB- Emphysematous cholecystitis# Advanced GB cancer# Cholecystoenteric fistula (Gallstone ileus)- WES Sign- Wall-Echo-Shadow: When a gallbladder is contracted around a gallstone, sometimes the only visualization of this is a shadow coming out of the liver. This is due to the stone's reflection that obscures the rest of the gallbladder. The three layers of the gallbladder wall of the anterior gallbladder are generally seen, followed by the echogenic stone which is followed by the shadow caused by the stone.- Imaging in acute cholecystitis:# Ultrasound (US) is the initial imaging study for the diagnosis of acute cholecystitis because it is performed relatively quickly and does not expose the patient to ionizing radiation. Ultrasound is much more accurate than plain film radiographs or CT (sensitivity is 88 % and specificity is 80 % of US). Furthermore, the modality is faster and more generally more readily available than cholescintigraphy or MRI.# US is not the most accurate imaging modality for the diagnosis of acute cholecystitis. Cholescintigraphy, usually in the form of the HIDA scan, is 97 % sensitive and 90 % specific (hence the investigation of choice). Radiopharmaceuticals such as 99mTc-labeled N-substituted iminodiacetic acids (HIDA, DIDA, DISIDA, etc.) are rapidly extracted from the blood and are excreted into the biliary tree in high concentration even in the presence of mild to moderate serum bilirubin elevations. Failure to image the gallbladder in the presence of biliary ductal visualization may indicate cystic duct obstruction, acute or chronic cholecystitis, or surgical absence of the organ. Such scans have some application in the diagnosis of acute cholecystitis.
HIDA scan
Ultrasonography
ERCP
PTC
G.I.T.