Investigation of choice for acute cholecystitis: March 2010
Ans. B: USG Plain Radiography: - Abdominal radiographs are usually not indicated, as most gallstones are not radio-opaque. - Chest radiographs may be performed to exclude a thoracic cause of pain and bowel perforation. Ultrasound: - Initial investigation of choice for suspected acute cholecystitis. Ultrasonographic signs of acute gallbladder inflammation include gallbladder wall thickening/oedema, pericholecystic fluid, gallstones, and positive ultrasonic Murphy's sign. - >90% diagnostic accuracy and varies with the morphologic criteria used. - Colour/power Doppler increases accuracy over Gray-scale sonography. - Advantages: allows evaluation of other abdominal structures (can identify an alternative diagnosis), provides preoperative information such as gallbladder size, stone size, gallbladder wall status, and the presence of biliary dilatation. Tc-IDA Radionuclide Scan: - Superior diagnostic accuracy and specificity compared to ultrasound. Used to clarify a negative, equivocal or technically difficult ultrasound in the presence of continued clinical suspicion of acute cholecystitis. - The hallmark of acute cholecystitis (acalculus as well as calculus) is persistent gall bladder non-visualisation 30 minutes post morphine or on the 3-4 hour delayed image. - False positives can occur in alcoholics, intensive care unit patients, patients on prolonged fasting, cystic fibrosis and chronic cholecystitis. - Morphine augmentation reduces false positives and is superior to delayed imaging. - In critically ill patients in whom acalculous cholecystitis is suggested on US, Tc-IDA scan with pretreatment cholecystokinin to empty gallbladder prior to Tc-IDA scan, or percutaneous cholecystostomy may be indicated. Post treatment Cholecystokinin can be used to evaluate gallbladder function in chronic cholecystitis. Limitations: longer examination time, unreliable in severe hepatocellular disease or at serum bilirubin levels >340-500 mmol/L, and inability to diagnose extra-biliary causes of acute right upper quadrant abdominal pain and to provide anatomical information. Other Imaging: Endoscopy or Barium studies may be indicated in ceain patients to identify alternative diagnoses which may clinically simulate acute cholecystitis. - Computed Tomography CT is useful when the clinical picture is non-specific as it can detect other intra-abdominal inflammatory processes, and when complications of acute cholecystitis are suspected. Sensitivities for CT diagnosis of acute cholecystitis have not been established CT features of acute cholecystitis include Pericholecystic inflammatory changes, including contrast enhancement of the liver adjacent to the gallbladder, inflammatory stranding of pericholecystic tissues, and pericholecystic fluid. Loss of distinction between walls of the gallbladder and adjacent liver. Gallbladder wall thickening, contrast enhancement. Gallbladder distension. Presence of gallstones. Advantages: allows other diagnoses, able to identify complications of acute cholecystitis. Limitations: exposure to ionising radiation, less sensitive (57%-88%) for detection of gallstones compared to ultrasound.
Plain Radiography
USG
CT scan
Barium studies