BILIARY STASIS HAEMOBILIA PNEUMOBILIA
Category: Diagnostic Radiology
Abstract : ECHOGENIC BILE Biliary stasis Fine echoes in the bile within the
gallbladder are not uncommon on an ultrasound scan. This is commonly due to the
inspissation of bile following prolonged starving, for example following
surgery. These appearances disappear after a normal diet is resumed and the
gallbladder has emptied and refilled. It occurs when the solutes in the bile
precipitate,
ECHOGENIC BILE
Biliary stasis
Fine echoes in the bile within the
gallbladder are not uncommon on an ultrasound scan. This is commonly due to the
inspissation of bile following prolonged starving, for example following
surgery. These appearances disappear after a normal diet is resumed and the
gallbladder has emptied and refilled.
It occurs when the solutes in the bile
precipitate, often due to hypomotility of the gallbladder, and can commonly be
seen following bone marrow transplantation and in patients who have undergone
prolonged periods (4–6 weeks) of total parenteral nutrition.
Prolonged
biliary stasis may lead to inflammation and/or infection, particularly in
postoperative patients and those on immunosuppression. Its clinical course
varies from complete resolution to progression to gallstones. However, following
the resumption of oral feeding, the gallbladder may contract and empty the
sludge into the biliary tree causing biliary colic, acute pancreatitis and/or
acute cholecystitis. For this reason, cholecystectomy may be considered in
symptomatic patients with biliary sludge. The fine echoes may form a
gravity-dependent layer and may clump together, forming ‘sludge balls’. To avoid
misdiagnosing sludge balls as polyps, turn the patient to disperse the echoes
rescan after the patient has resumed a normal diet. Biliary stasis is associated
with an increased risk of stone formation.
Biliary
crystals
Occasionally, echogenic bile persists even with normal gallbladder
function. The significance of this is unclear. It has been suggested that there
is a spectrum of biliary disease in which gallbladder dysmotility and subsequent
saturation of the bile lead to the formation of crystals in the bileand also in
the gallbladder wall, leading eventually to stone formation. Pain and biliary
colic may be present prior to stone formation and the presence of echogenic bile
seems to correlate with the presence of biliary crystals. Biliary crystals, or
‘microlithiasis’ (usually calcium bilirubinate granules) have a strong
association with acute pancreatitis and its presence in patients who do not have
gallstones is therefore highly significant.
Obstructive causes of biliary
stasis
Pathological bile stasis in the gallbladder is due to obstruction of
the cystic duct (from a stone, for example) and may be demonstrated in a
normalsized or dilated gallbladder. The bile becomes viscous and hyperechoic.
The biliary ducts remain normal in calibre. Eventually the bile turns watery and
appears echo-free on ultrasound; this is known as a mucocoele. Bile stasis
within the ducts occurs either as a result of prolonged and/or repetitive
obstruction or as a result of cholestatic disease such as primary biliary
cirrhosis (PBC) or PSC. This can lead to cholangitis.
Haemobilia
Blood
in the gallbladder can be the result of gastrointestinal bleeding or other
damage to the gallbladder or bile duct wall, for example iatrogenic trauma from
an endoscopic procedure. The appearances depend upon the stage of evolution of
the bleeding. Fresh blood appears as fine, low-level echoes. Blood clots appear
as solid, nonshadowing structures and there may be hyperechoic, linear strands.
The history of trauma will allow the sonographer to differentiate from other
causes of haemobilia and echogenic bile, particularly those associated with
gallbladder inflammation, and there may be other evidence of abdominal trauma on
ultrasound such as a haemoperitoneum.
Pneumobilia
Air in the biliary
tree is usually iatrogenic and is frequently seen following procedures such as
ERCP, sphincterotomy or biliary surgery. Although it does not usually persist,
the air can remain in the biliary tree for months or even years and is not
significant. It is characterized by highly reflective linear echoes, which
follow the course of the biliary ducts. The air usually casts a shadow which is
different from that of stones, often having reverberative artefacts and being
much less well-defined or clear. This shadowing obscures the lumen of the duct
and can make evaluation of the hepatic parenchyma difficult. Pneumobilia may
also be present in emphysematous cholecystitis, an uncommon complication of
cholecystitis in which gas-forming bacteria are present in the gallbladder (see
above), or in cases where a necrotic gallbladder has formed a cholecystoenteric
fistula. Rarely, multiple biliary stones form within the ducts throughout the
liver and can be confused with the appearances of air in the ducts.
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