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Dilated CBD

1/16/13 -  The IOW comes to us from Drs. Hiren Patel, EZ Numur, Deepa Patel, and Emory medical student Kathryn West. This group captured excellent views of the common bile duct (CBD) during a bedside right upper quadrant (RUQ) ultrasound. 

Image 1:  CBD

GB CBD CF

The above image shows a fluid filled gallbladder with multiple hyperechoic stones and associated shadowing. However, there is no visible gallbladder wall thickening or peri-cholecystic fluid (PCF). If we stop here, the patient gets an ED diagnosis of cholecystitis. Evaluating the CBD completes the bedside biliary exam - and in this case reveals the true pathology, choledocolithiasis. As labeled in the attached image, the tubular hypoechoic structure is the CBD. Recall that the CBD is part of the portal triad that includes the hepatic artery and portal vein. As seen in the above image, the use of color-flow Doppler helps to differentiate these structures. Both the portal vein and hepatic artery have visible color flow (portal vein is labeled), while the CBD has no visible flow on ultrasound. 

When distended by a stone, the CBD diameter enlarges and can be more readily seen. The normal width of the CBD is 4mm for patients less than 50 years old with one additional millimeter allowed for every decade over 40. Seeing the stone itself in the CBD is much less common and not necessary – the dilated CBD is suggestive enough.

For some additional reading and evidence on the topic, the linked article (Summers et al, 2010) published in Annals of EM illustrates the similar test characteristics of ED provider performed bedside ultrasound vs radiologists in the setting of suspected acute cholecystitis. 

Happy scanning and thank you for your continued use of bedside ultrasound.

John Lemos, MD, MPH
Clinical Instructor
Department of Emergency Medicine
Emory University