Diagnostic ultrasound ( PDFDrive )

176 PART II Abdominal and Pelvic Sonography
A
B
FIG. 6.13 Pneumobilia. (A) Extensive air within the central ducts manifests as linear echogenic structures paralleling the portal veins. Note
the dirty shadowing (arrow) and ring-down artifact. (B) Air in the gallbladder. Pneumobilia often extends into the gallbladder. Note the ring-down
artifact (arrow).
Extensive arterial calciications, seen especially in diabetic patients,
can mimic pneumobilia.
Biliary Tree Infection
Acute (Bacterial, Ascending) Cholangitis
Antecedent biliary obstruction is an essential component of
bacterial cholangitis, associated in 85% of cases with CBD stones. 27
Other causes of obstruction include biliary stricture as a result
of trauma or surgery, congenital abnormalities such as choledochal
cysts, and partially obstructive tumors. Intrinsic or extrinsic
neoplasms causing complete biliary obstruction rarely cause
pyogenic cholangitis before biliary intervention. 19 he clinical
presentation is usually that of (1) fever (≈90%), (2) RUQ pain
(≈70%), and (3) jaundice (≈60%), the classical Charcot triad.
here is leukocytosis, or at least a let shit, and elevated levels
of serum alkaline phosphatase and bilirubin in the great majority
of patients. Oten, mild serum hepatic transaminitis is present,
but occasionally, levels above 1000 are seen early in the disease
because of a sudden increase in intrabiliary pressures. 19 he bile
is most oten infected by gram-negative enteric bacteria, which
are oten retrieved in blood cultures.
Acute cholangitis is a medical emergency. Sonography is
advocated as the irst imaging modality to determine the cause
and level of obstruction and to exclude other diseases, such as
cholecystitis, acute hepatitis, and Mirizzi syndrome. Sonography
is more accurate than CT and more practical than MRI, endoscopic
ultrasound, and ERCP in the initial assessment of patients
with potential acute biliary disease. 28
he sonographic indings of bacterial cholangitis include
the following (Fig. 6.14):
• Dilation of the biliary tree
• Choledocholithiasis and possibly sludge
• Bile duct wall thickening
• Hepatic abscesses
Dilation of the biliary tree, when present, can be diagnosed
by sonography. A CBD diameter greater than 6 mm is considered
abnormal in most patients. Subtle dilation of the intrahepatic
biliary tree is a frequently overlooked inding that should be
speciically sought. his includes use of subcostal oblique scanning
of the porta hepatis to assess the caliber of the right and let
hepatic ducts, as well as evaluation of the CBD, which may
measure normal but still show a somewhat “tense” or distended
morphology. Dilation of the biliary tree is seen in 75% of patients.
he obstructive stone is usually lodged in the distal CBD but
may be mobile, causing intermittent obstruction. Air is rarely
seen within the ducts; thus its presence suggests a choledochoenteric
istula in the absence of previous biliary manipulation
(Fig. 6.15, Video 6.4). Circumferential thickening of the
bile duct wall, similar to other causes of cholangitis, may
be present and may extend to the gallbladder. Multiple small
hepatic abscesses—sometimes grouped in a lobe or segment
of the liver—may be seen but tend to become visible on sonography
when they have undergone liquefaction and are a late
inding.
Liver Flukes
Fascioliasis. Fasciola hepatica infection is unevenly endemic
in many regions of the world, including Asia, Europe, Northern
Africa, and South America (mainly Peru and Bolivia). 29 Infection
is caused by consumption of water or raw vegetables contaminated
with the larvae (metacercariae) of the F. hepatica luke. he
infection has two stages: the acute phase, lasting 3 to 5 months,
and the chronic phase, which may last several years to over a
decade. he acute phase corresponds to the migration of the