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Tips & Tricks for Ultrasound Evaluation of the Gall Bladder & RUQ
01 Know Your Limitations: Ultrasound may help clarify findings elicited by a thorough history and physical exam. When used correctly, it can greatly improve diagnostic accuracy, and help guide patient management, especially for time-critical diagnosis and treatment of unstable patients. If you use ultrasound in your ED, your department should have a quality improvement program set up that is approved by both ED administration and radiology.
02 Don’t Anchor: A good sonographer or sonologist will perform an ultrasound without forming a diagnosis first. If you scan with a definitive diagnosis in mind, you put yourself at risk for capturing the images that support your diagnosis. Be thorough and systematic with every scan you perform. The goal is to use your sonographic findings as additional data to help you solve the case.
03 The Sonographic Murphy’s Sign: To check for a sonographic Murphy’s sign, which is a sign of cholecystitis, place the ultrasound probe at the maximal point of tenderness in the right upper quadrant. If the probe is placing direct pressure on the gallbladder fundus, you have a positive sonographic Murphy’s sign. False negatives may occasionally occur if the patient has received opiates prior to examination.
04 The Gallbladder Wall: One sign of cholecystitis is a thickened gall-bladder wall. The normal gallbladder wall can be up to 3mm thick. The most common conditions other than cholecystitis that may cause thickening of the gallbladder wall include hepatitis, hypoalbuminemia, tumor, hyperplastic cholecystosis, adenomyomatosis, and CHF. The presence of pericholecystic fluid, in the absence of ascites also supports the diagnosis of acute cholecystitis. If there is any uncertainty, a nuclear biliary scan (HIDA or DESIDA scan) may be performed.
05 The Common Bile Duct: A dilated common bile duct may be present in acute cholecystitis or with ductal obstruction from choledolcholithiasis. The normal common bile duct inner diameter should be less than 6mm, but may be higher, up to 10mm, post-cholecystectomy. In addition the diameter may be higher in older patients, up to 1mm per decade of life after 60 years of age.
06 The Gallbladder Contents: Look for a dilated gallbladder, evidence of stones, and for sludge. Gallstones should be mobile, unless they are impacted in the gallbladder neck, and should cast an acoustic shadow. If all stones are mobile in a patient who remains symptomatic, consider that they may be a red-herring and not the true cause of the patient’s pain. Remember that approximately 15% of adults have asymptomatic gallstones. If there are no sonographic signs of cholecystitis, but a gallstone is impacted (non-mobile) in the gallbladder neck, be suspicious for early cholecystitis and consider admission, additional imaging or at minimum, next-day follow-up.
07 Pitfalls: Don’t miss a single obstructing gallstone hidden in the gallbladder neck. Also, do not miss a AAA because you did not look. It is not that far away, and should be checked routinely in anyone over the age of 50 who is having an abdominal ultrasound for another reason.
Brady Pregerson manages a free on-line EM Ultrasound Image Library and is the editor of the Emergency Medicine Pocketbook series. For more information visit EMresource.ORG.
Teresa S. Wu is the Associate Residency Director, and Director of Ultrasound and Simulation Programs and Fellowships, for the Maricopa Emergency Medicine Program in Phoenix, Arizona.