Diagnostic ultrasound ( PDFDrive )

CHAPTER 6 The Biliary Tree and Gallbladder 181
contents may be hypoechoic or echogenic, and the stones may not
show shadowing. With severe atrophy of the afected segment,
minimal liver parenchyma may be present, and the crowded,
stone-illed ducts may appear as a single, heterogeneous mass.
Ascariasis
Ascaris lumbricoides is a parasitic roundworm estimated to infect
up to one-quarter of the world’s population. It uses a fecal-oral
route of transmission and is most common in children, presumably
because of their lower hygiene. 38 he worm is generally 20
to 30 cm long and up to 6 mm in diameter. It is active within the
small bowel and may enter the biliary tree retrogradely through
the ampulla of Vater, causing acute biliary obstruction. Generally,
infected patients are asymptomatic but may present with biliary
colic, cholangitis, acalculous cholecystitis, or pancreatitis.
he appearance of biliary ascariasis on sonography depends
on the number of worms within the bile ducts at the time of the
study. Most oten, a single worm is identiied that appears as a
tube or as parallel echogenic lines within the bile ducts. he
appearance is similar to a biliary stent, which should be excluded
on clinical history. On the transverse view, the rounded worm
surrounded by the duct wall gives a target appearance. he worm
may be folded on itself or may occupy any portion of the ductal
system, including far into the liver parenchyma, close to the
capsule, or within the gallbladder. Movement of the worm during
the scan facilitates the diagnosis. When infestation is heavy,
multiple worms may lie adjacent to each other within a distended
duct, resembling spaghetti. Occasionally, the worms may appear
as an amorphous, echogenic illing defect, making the diagnosis
more diicult. 38
HIV Cholangiopathy
Also known as acquired immunodeiciency syndrome (AIDS)
cholangitis, human immunodeiciency virus (HIV) cholangiopathy
is an inlammatory process afecting the biliary tree in
the advanced stages of HIV infection. It is most oten caused by
an opportunistic infection and therefore occurs in patients with
CD4 counts of less than 100. Patients present with severe RUQ
pain or epigastric pain, a nonicteric cholestatic picture, and greatly
elevated serum alkaline phosphatase with a normal bilirubin
level. In most patients a pathogen is recovered, usually Cryptosporidium
or, less oten, cytomegalovirus. 39
Sonography has been advocated as the irst imaging test for
assessment of HIV cholangiopathy (Fig. 6.21). A negative scan
A
B
C
D
FIG. 6.21 HIV Cholangiopathy. (A) Intrahepatic biliary tree. Note the thick rind of echogenic tissue (arrowheads) surrounding the central portal
triads and causing irregular narrowing of the bile ducts. (B) Common bile duct (CBD) is dilated, and its wall is minimally irregular. (C) Papillary
stenosis. The dilated CBD abruptly tapers in an echogenic, inlamed ampulla (arrowhead). (D) Transverse view of ampulla (arrow), which is enlarged
and echogenic, viewed in the caudal aspect of pancreatic head.