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ABDOMINAL ULTRASOUND
Figure 3.14 Mirizzi syndrome: a large stone in the
neck of the gallbladder (arrow) is compressing the bile
duct, causing intrahepatic duct dilatation. The lower end
of the CBD remains normal in calibre.
THE CONTRACTED OR SMALL
GALLBLADDER
Postprandial
The most likely cause is physiological and due to
inadequate preparation. The normal gallbladder
wall is thickened when contracted, and this must
not be confused with a pathological process.
Always enquire what the patient has recently eaten
or drunk (Fig. 3.15).
Pathological causes of a small gallbladder
Most pathologically contracted gallbladders contain
stones.
When the gallbladder cannot be identified, try
scanning transversely through the gallbladder
fossa, just caudal to the porta hepatis. Strong shadowing
alerts the sonographer to the possibility of a
contracted gallbladder full of stones. The reflective
surface of the stones and distal shadowing are
apparent and the anterior gallbladder wall can be
demonstrated with correct focusing and good
technique (Fig. 3.16).
Do not confuse the appearances of a previous
cholecystectomy, when bowel in the gallbladder
fossa casts a shadow, with a contracted, stone-filled
gallbladder.
A less common cause of a small gallbladder is
the microgallbladder associated with cystic fibrosis
Figure 3.15 Postprandial, contracted gallbladder, with
consequently thickened wall.
(Fig. 3.17). The gallbladder itself is abnormally
small, rather than just contracted. Cystic fibrosis
also carries an increased incidence of gallstones
because of the altered composition of the bile and
bile stasis and the wall might be thickened and
fibrosed from cholecystitis.
PORCELAIN GALLBLADDER
When the gallbladder wall becomes calcified the
resulting appearance is of a solid reflective structure
causing a distal shadow in the gallbladder
fossa (Fig. 3.18). This can be distinguished from a
gallbladder full of stones where the wall can usually
be seen anterior to the shadowing (Fig 3.16).
A porcelain gallbladder probably results from a
gallbladder mucocoele—a long-standing obstruction
of the cystic duct, usually from a stone. The
bile inside the non-functioning gallbladder is gradually
replaced by watery fluid, the wall becomes
fibrotic and thickened and ultimately calcifies.
There is an association between porcelain gallbladder
and gallbladder carcinoma, so a prophylactic
cholecystectomy is usually performed to
pre-empt malignant development. 8
The shadowing from the anterior gallbladder
wall obscures the gallbladder contents, and can
mimic bowel in the gallbladder fossa. A plain
X-ray also clearly demonstrates the porcelain
gallbladder.