For evaluation of biliary colic, cholecystitis, hepatomegaly, and ascites
Rosen et al. reported 91% sensitivity using only sonographic Murphy’s for cholecystitis (Am J Emerg Med 19:32, 2001)
The hungrier the patient, the better the scan
Usually scan in supine, but LLR or having the patient sit upright may help locate GB or document mobility of stones.
Evaluation of Biliary Colic and Cholecystitis
Start c probe in sagittal and abdominal midline just below the rib line. Find liver parenchyma and then move the probe laterally until GB can be seen, usually in the midclavicular line. Angle probe cephalad so you can scan under the rib. If the GB is not initially visualized, have the patient take a deep breath and hold it, which will drop the liver below the rib line. Obtain a longitudinal scan of the fundus, body and neck. To assure it is the GB, trace the neck to communication with the portal triad which should lie medial and superior to the GB. This is the only way to prove that the structure in question is not a loop of bowel or a slice of the IVC.
The entire GB should be scanned in longitudinal and transverse for stones, fluid, sludge, and wall thickening. The gallbladder’s wall is triple layered (railroad tracks).
Wall thickness should be measured while in transverse on the anterior wall. <3 mm is normal (in a contracted gall bladder, the wall may appear thickened.) It will usually be >5 mm in chronic, and >9 mm in acute cholecystitis.
A contracted GB may have non-pathologic wall thickening
Evaluate the fundus for sonographic Murphy’s.
To find the portal triad (portal vein, common bile duct, and hepatic artery) position the probe in the right epigastric area with the indicator towards the right axilla. This should demonstrate the portal vein in longitudinal with the common bile duct and/or hepatic artery above (sandwich sign).
Sandwich Sign: CBD (Enlarged) above Portal Vein
If the probe is now rotated 90° counterclockwise, the portal vein is now seen in transverse with the CBD and Hepatic artery above it (Mickey Mouse Sign.)
Mickey Mouse Sign (Arrow is probably CBD, arrowhead is probably HA)
It is beneficial to measure both ears of Mickey, because though the CBD is often lateral, it is variable, and hepatic artery enlargement is extremely rare. If the triad can not be located, try tracing the branches of the portal vein to the towards the hilum. Branches of the portal system have echogenic walls and are normally larger than the hepatic venous system which has hypoechoic walls. The branches of the hepatic artery are rarely visible distant from the hilum. The normal size of the CBD is 1 mm for every 10 yrs of age or absolute of 7mm.
Evaluation of Hepatomegaly
Get the FAST exam view of Morrison’s pouch. If the liver extends below the inferior pole of the kidney, then there is hepatomegaly. Other confirmatory signs are ascites, thickening of GB wall, and splenomegaly. Also the kidney is normally hypoechoic to the liver parenchyma, if it is the same echogenicity as kidney, consider fatty infiltration. Also, can measure from diaphragm to inferior tip of liver, >15 is megaly.
Evaluation of Cirrhosis
Evaluation of Ascites
Perform same scan as FAST
Gallbladder Abnormalities
Shadows should be present with stones >4mm. The shadows should be clean anechoic areas. If the shadow looks dirty, it might be bowel gas.
Stones should lie in the dependant portion of the GB and should move with patient positioning, unless impacted in the neck. WES (Wall Echo Shadow) is commonly seen in gallstone filled GBs. It consists of an anterior echogenic wall, an intervening anechoic stripe from bile, a posterior echogenic line representing stone material, and a prominent posterior acoustic shadow.
Sludge
Jaundice and Biliary Obstruction
If extrahepatic dilation is seen then the common duct is obstructed, this will eventually back up to the intrahepatic ducts which will appear as tubular structures with echogenic walls, they can look like the antlers of a deer.
Common Variants and Selected Abnormalities
Phrygian Cap
Agenesis of GB
Sepatations of the Lumen
Pitfalls
· Misidentifying Gallbladder. Ensure it is GB by tracing neck to main lobar fissure to portal triad
· Inadequate visualization of GB and biliary system. Bowel gas or high liver can prevent visualization. Firm pressure, angling, pt breaths, pt positioning can overcome these obstacles.
· Confusion of GB neck shadows without stone visualization. The spiral valves of Hester in the neck can give shadowing. Bowel gas shadowing is dirty (indistinct), stones should give clean shadows.
· Misdiagnosis of dilated intrahepatic ducts. Branches of the portal system can be confused with the ducts. Color Doppler scanning or tracing the ducts to the CBD can assure accuracy.
· Ascites look the same as fresh blood and vice versa.
Quality Assurance
6 Views:
Gall Bladder
1 Long Axis showing whole GB
3 Transverse (high, middle, low)
Porta Hepatis
1 View showing Mickey Mouse or Sandwich c CBD measured black to black
Liver
1 large transverse cut showing liver parenchyma
Evaluate:
Sonographic Murphy’s
Stones/Sludge
GB Wall thickness
Pericholecystic Fluid
Intrahepatic Cholestasis
Liver Abnormalities
Diagnosis