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ABDOMINAL ULTRASOUND
A
●
B
C
Figure 3.29 Emphysematous cholecystitis. (A) and (B)
TS and LS with gas and debris in the gallbladder lumen.
(C) Gas in the gallbladder lumen completely obscures the
contents.
lodged just distal to the confluence of the
biliary and pancreatic ducts.
Dilatation of the gallbladder alone (that is
without ductal dilatation) is usually caused by,
obstruction at the neck or cystic duct (Fig. 3.8).
To assess whether the gallbladder is pathologically
dilated may be difficult on ultrasound. The
sonographer should look at both the size and
Figure 3.30 X-ray demonstrating gas in the gallbladder
in emphysematous cholecystitis.
shape; the dilated gallbladder will have a rounded,
bulging shape due to the increase in pressure inside
it. A gallbladder whose wall has become fibrosed
from chronic cholecystitis due to stones will often
lose the ability to distend, so the biliary ducts can
look grossly dilated despite the gallbladder remaining
‘normal’ in size, or contracted.
Early ductal obstruction
Beware very early common duct obstruction, before
the duct becomes obviously dilated. The duct may
be mildly dilated at the lower end, just proximal to a
stone. Likewise intermittent obstruction by a small
stone at the lower end of the duct may be nondilated
by the time the scan is performed (Fig. 3.10).
A significant ultrasound feature in the absence
of any other identifiable findings is that of thickening
of the wall of the bile duct. This represents an
inflammatory process in the duct wall, which may
be found in patients with small stones in a nondilated
duct, but is also associated with sclerosing
cholangitis. 23
It is sometimes technically difficult in some
patients (particularly those with diffuse liver disease)
to work out whether a tubular structure on