Ultrasound - Biliary

Indications

To assess and exclude the presence of:

Cholelithiasis

Cholecystitis

Common bile duct obstruction

Consider in the following presentations:

Right upper quadrant pain

Undifferentiated fever or shock

Jaundice

Contraindications (absolute in bold)

Airway management or resuscitation required

Alternatives

Formal ultrasound scan

CT scan

Magnetic resonance cholangiopancreatography (MRCP)

Informed consent

Medical emergency

Consent is not required if the patient lacks capacity or is unable to consent

Brief verbal discussion is recommended if the situation allows

or

Verbal consent

Less complex non-emergency procedure with low risk of complications

Potential complications

Failure to visualise gallbladder (bowel gas, excess tissue, pain, full of stones)

Failure of image interpretation (false negative or positive)

Procedural hygiene

Standard precautions

PPE: non-sterile gloves

Area

Any bed

Staff

Procedural clinician

Equipment

Towel

Ultrasound machine and gel

Curvilinear ultrasound probe (abdominal pre-set or adjust depth to centre important structures)

Positioning

Supine with hips flexed to relax the abdominal muscles

Roll patient onto the left side if possible (encourages stones out of the gallbladder neck)

Probe inferior to the costal margin right of midline with marker to the right or head

Sequence (scanning gallbladder)

Place probe inferior to the costal margin right of midline with marker to head

Sweep probe laterally below the costal margin maintaining liver margin in the field of view

Locate the gallbladder and assess for tenderness with probe pressure (sonographic Murphy’s sign)

Scan entirely though its long and short axes including the gallbladder neck

Identify any echogenic gallstones with distal shadowing

If present, roll patient onto left side and confirm stones move (failure indicates impaction or a mass)

Consider rescanning with the probe in a different position (improving sensitivity)

Assess for pericholecystic fluid (if found perform a FAST scan to exclude ascites as a cause)

Measure the anterior gallbladder wall between the lumen and the hepatic parenchyma (>3mm is abnormal)

In a longitudinal view identify the portal triad distal to the gallbladder neck (see below)

Identify the common bile duct (Mickey Mouse’s right ear)

Rotate the probe 90 degrees anticlockwise maintaining location (marker turned towards the right)

Confirm common bile duct anterior to portal vein by demonstrating no flow on colour Doppler

Measure common duct from inner wall to inner wall (abnormal if greater than 6mm)

Sequence (improving view over gallbladder obscured by bowel gas)

Asking patient to take and hold a deep breath (lowering liver and improving sonographic window)

Lie patient on their left side (using gravity to move the liver and gallbladder forward)

Maintain constant downward pressure with the probe over the area of poor view

Fan probe in the windows above and below the sonographic obstacle to obtain a view

Try an intercostal approach with transducer oriented and swept along an intercostal space

Post-procedure care

Clean ultrasound gel from patient

Initiate further management if required

Document (indication, structures identified, interpretation)

Tips

Gallbladder location, size, shape and axis are variable

The biliary ultrasound is difficult, and a normal exam should not outweigh high clinical suspicion

Biliary sludge is echogenic in appearance but does not cast an acoustic shadow

Failure to identify the gallbladder should warrant additional diagnostic imaging (ultrasound, CT, MRCP)

Discussion

Ultrasonography is the procedure of choice in suspected gallbladder or biliary disease. It is the most sensitive and specific test for the detection of gallstones. CT scanning may be useful when diagnosis is less certain or when ultrasound is unavailable. CT scans can demonstrate gallbladder wall thickening, common bile duct dilation and pericholecystic stranding, but only show 75% of gallstones.

Gallstones appear echogenic in dependent areas with acoustic shadowing beneath. Cholecystitis is diagnosed by the presence of gallstones plus a sonographic Murphy’s sign and anterior wall thickness greater than 3mm. In severe cases, pericholecystic fluid may also be present. Gallbladder wall thickening alone may be physiological (post-prandial) or occur with oedematous states.

Measuring the common bile duct diameter (to exclude biliary obstruction) is the most challenging part of the examination. The key step is to find the portal vein which is located close to the common bile duct and hepatic artery (the portal triad).

The short axis of the portal vein can be found by visualising the gallbladder in its long axis and following the thin hyperechoic line of the main lobar fissure extending from the neck of the gallbladder to the portal vein. The portal vein (dot) and gallbladder (line) should appear as an exclamation mark. With probe adjustment, the hepatic artery and common bile duct can be brought into view on either side of the portal vein with the appearance of Mickey Mouse’s ears. Mickey Mouse’s right ear is the common bile duct, which can be confirmed by colour Doppler imaging to demonstrate no flow within the duct. Once this view is obtained the probe can be rotated 90 degrees anticlockwise to obtain a long axis view of the portal vein with the smaller common bile duct anterior (confirmed with lack of Doppler flow). Measurement should be taken from inner wall to inner wall of the common bile duct. Normal width of the common bile duct is less than 4mm or 1mm for every decade of age (<10mm post cholecystectomy).

An alternative method is to start imaging the liver in the transverse plane and look directly for the portal vein, which is then traced to the gallbladder and visualised in the longitudinal plane (creating the same view with the common bile duct anterior to portal vein). The portal vein is a high-pressure vein which can be distinguished from the hepatic veins (the only other large vessels) due to its thicker echogenic walls.

Peer review

This guideline has been reviewed and approved by the following expert groups:

Emergency Care Institute

Please direct feedback for this procedure to ACI-ECIs@health.nsw.gov.au.

References

Roberts JR, Custalow CB, Thomsen TW. Roberts and Hedges’ clinical procedures in emergency medicine and acute care. 7th ed. Philadelphia, PA: Elsevier; 2019.

Dunn RJ, Borland M, O’Brien D (eds.). The emergency medicine manual. Online ed. Tennyson, SA: Venom Publishing; 2019.

Jeffery J, et al (2020): In: UpToDate. Waltham (MA): UpToDate.: Clinical features and diagnosis of abdominal aortic aneurysm

Emergency ultrasound imaging criteria compendium. Ann Emerg Med. 2016;68(1):e11-e48. doi:10.1016/j.annemergmed.2016.04.028

Dawson M, Mallin M. Introduction to bedside ultrasound: volume 1. New York NY: Apple Books; 2013.

Dawson M, Mallin M. Introduction to bedside ultrasound: volume 2. New York NY: Apple Books; 2013.

Brunetti J. Imaging in gallstones (cholelithiasis). Medscape. 2018 Oct 2. WebMD LLC. Available from: https://emedicine.medscape.com/article/366246-overview

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