DOI:10.2214/AJR.06.1172
AJR 2007; 188:1596-1603
© American Roentgen Ray Society
Parasitic Diseases of the Biliary Tract
Jae Hoon Lim1,
So Yeon Kim2 and
Cheol Min Park3
1 Department of Radiology and Center for Imaging Science, Samsung Medical
Center, Sungkyunkwan University School of Medicine, 50 Ilwon-dong, Kangnam-ku,
Seoul 135-230, South Korea.
2 Department of Radiology, Asan Medical Center, Seoul, South Korea.
3 Department of Radiology, Guro Hospital, Korea University, Seoul, South
Korea.
Received September 1, 2006;
accepted after revision November 8, 2006.
Address correspondence to J. H. Lim.
Abstract
OBJECTIVE. Parasites residing in the biliary tree include
Clonorchis sinensis, Opisthorchis viverrini, Opisthorchis felineus,
and Fasciola hepatica. They are willowy, leaf-like, flat flukes
dwelling in the bile ducts and gallbladder. Human ascarides, Ascaris
lumbricoides, dwelling in the small intestine, inadvertently migrate into
the bile ducts and cause biliary obstruction. The purpose of this article is
to illustrate typical imaging findings of liver fluke infection and biliary
ascariasis.
CONCLUSION. Adult flukes of Clonorchis and
Opisthorchis measure 8–15 mm and adult flukes of
Fasciola measure 20–40 mm in length. The presence of flukes in
the bile ducts causes dilatation of the bile ducts, varying degrees of chronic
inflammation followed by adenomatous hyperplasia, and bile duct wall
thickening. Imaging findings of clonorchiasis and opisthorchiasis include
visualization of adult flukes in the bile ducts and gallbladder, diffuse
dilatation of the peripheral small intrahepatic bile ducts with no or minimal
dilatation of the large bile ducts, and thickening of the bile duct wall. In
biliary fascioliasis and ascariasis, adult worms are visualized in the dilated
bile ducts and gallbladder.
Keywords: biliary system • CT • infectious diseases • MRI • sonography
Introduction
Parasitic diseases are prevalent in some endemic areas, but such diseases
may now have more extensive geographic distribution because of increased
travel. Thus, sporadic cases are encountered among immigrants in nonendemic
areas. The trematodes (flukes) that commonly infect the human biliary tract
include Clonorchis sinensis, Opisthorchis viverrini, Opisthorchis
felineus, and Fasciola hepatica. The majority of patients are
asymptomatic, with symptoms limited mostly to heavily infected persons.
Ascaris lumbricoides residing in the small intestine may migrate into
aberrant sites, mostly into the bile duct through the duodenal papilla, and
cause biliary colic and obstructive jaundice. Parasitic diseases usually
present with characteristic imaging findings. However, they sometimes present
with nonspecific findings and may be mistaken for malignant tumors because the
diseases may produce a mass. This article reviews the radiologic appearances
of biliary parasitic diseases, focusing on those with relatively specific
findings.
Clonorchiasis and Opisthorchiasis
Clonorchiasis and opisthorchiasis are trematodiases caused by chronic
infestation of liver flukes, C. sinensis, O. viverrini, and O.
felineus. These three parasites are closely related trematodes and have
similar life cycles and the same pathophysiology and disease manifestations
[1,
2]. They are different only in
geographic distribution. C. sinensis is endemic in Northeast China,
Korea, Taiwan, and Vietnam; O. viverrini is endemic in Laos and
Thailand; O. felineus is found in parts of Eastern Europe and the
former U.S.S.R. In some endemic areas, particularly in Southeast Asia,
millions of people are infected with liver flukes.
Adult C. sinensis and O. viverrini are flat, elongated,
leaflike, flabby, and tapered anteriorly and somewhat rounded posteriorly
(Fig. 1). Their size ranges
from 8.0 to 15.0 mm long by 1.5–4.0 mm wide, and they are about 1.0 mm
thick [1]. In vivo, flukes may
persist for 15–20 years or more. When a person ingests the flesh of raw
fish containing metacercariae, cysts are freed from the flesh. The larva
excyst and migrate from the duodenum via the ampulla of Vater into the bile
ducts, where they mature to adult worms in about 25 days. The adult flukes
reside in the medium-sized and small intrahepatic bile ducts
(Fig. 2) and, occasionally, in
the extrahepatic bile ducts, gallbladder, and pancreatic duct. The result is
mechanical obstruction, inflammatory reaction, adenomatous hyperplasia, and
periductal fibrosis [1,
2].
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Fig. 1 —Gross appearance of adult Clonorchis sinensis
collected from feces. Flukes measure 8–15 mm long, 1.5–4.0 mm
wide, and 1.0 mm thick (scale increment = 1 mm). (Reprinted with permission
from Lim JH, Ko YT, Lee DH, Kim SY. Clonorchiasis: sonographic findings in 59
proved cases. AJR 1989; 152:761–764
[5])
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Fig. 2 —Photomicrograph of pathologic specimen shows adult fluke of
Clonorchis sinensis in intrahepatic bile duct. Note adenomatous
hyperplasia of mucosa and severe fibrous thickening of bile duct wall
(arrows). (Masson's trichrome stain x40)
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Cholangiographic Findings
Cholangiograms show many elongated filling defects from a few millimeters
to 10 mm in length—sizes compatible with fluke dimensions—and
intrahepatic duct dilatation, which is more pronounced in the peripheral
regions [1,
3,
4]
(Fig. 3). The filling defects
within the bile ducts represent adult flukes. The defects are linear, round,
filamentous, ricelike, oval, or elliptic and mostly occur within the smaller
intrahepatic bile ducts—that is, tertiary, quaternary, and more
peripheral tributaries [1,
3,
4].
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Fig. 3 —45-year-old man with clonorchiasis. Endoscopic retrograde
cholangiogram shows innumerable elongated or elliptic small filling defects,
indicating adult Clonorchis sinensis (arrows) in peripheral
small branches of bile ducts. Many peripheral bile ducts are occluded by
flukes (arrowheads).
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Sonographic, CT, and MR Cholangiographic Findings
Flukes within the bile ducts are usually difficult to visualize on
sonography or CT [1,
5]
(Fig. 4). With the advent of
high-resolution sonographic and CT equipment, the flukes or aggregates of
flukes can be shown as nonshadowing echogenic foci or casts within the bile
ducts.
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Fig. 4 —65-year-old man with clonorchiasis. Sonogram of right hepatic
lobe shows prominent and echogenic biliary radicles up to periphery,
indicating severe thickening of peripheral bile ducts by chronic inflammatory
change caused by Clonorchis sinensis infection.
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On the other hand, flukes within the gallbladder are much easier to see
[5]. There may be floating or
dependent, discrete, and nonshadowing echogenic foci in the lumen
(Fig. 5). Usually flukes sink
in the dependent portion but float and change in position in reaction to a
light blow to the gallbladder with the transducer. Flukes occasionally float
spontaneously, and these motions are considered to be caused by the movement
of living flukes [5].
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Fig. 5 —75-year-old man with severe clonorchiasis. Sonogram of
gallbladder shows several small floating and elongated objects indicating
adult Clonorchis sinensis. Sometimes these filling defects move
spontaneously in bile.
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Like cholangiograms, sonograms, CT scans, and MR cholangiograms show
diffuse, uniform dilatation of the small intrahepatic bile ducts with no or
minimal dilatation of the large bile ducts and no focal obstructing lesions
[1,
6,
7] (Figs.
6,
7A,
7B,
7C,
7D,
8A,
8B). Flukes are living in the
peripheral small and medium-sized bile ducts, resulting in longstanding
incomplete obstruction, but flukes are not visible on images because they are
very thin. In a heavy infection, many small low-intensity filling defects are
evident on MR cholangiograms (Fig.
8A,
8B) or CT scans
[1]. Thickening of the bile
duct wall may be evident on sonograms and CT scans
[1]
(Fig. 4).
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Fig. 7A —55-year-old man with moderate infection of Clonorchis
sinensis. Contrast-enhanced portal venous CT images show profound
dilatation of peripheral small bile ducts up to peripheral margin of liver.
Central (large) intrahepatic ducts and extrahepatic ducts are not dilated
(arrows, B and C).
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Fig. 7B —55-year-old man with moderate infection of Clonorchis
sinensis. Contrast-enhanced portal venous CT images show profound
dilatation of peripheral small bile ducts up to peripheral margin of liver.
Central (large) intrahepatic ducts and extrahepatic ducts are not dilated
(arrows, B and C).
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Fig. 7C —55-year-old man with moderate infection of Clonorchis
sinensis. Contrast-enhanced portal venous CT images show profound
dilatation of peripheral small bile ducts up to peripheral margin of liver.
Central (large) intrahepatic ducts and extrahepatic ducts are not dilated
(arrows, B and C).
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Fig. 7D —55-year-old man with moderate infection of Clonorchis
sinensis. Endoscopic retrograde cholangiogram shows characteristic
diffuse dilatation of intrahepatic bile ducts, especially peripheral small
bile ducts. Right and left hepatic ducts and extrahepatic bile ducts are not
dilated. There are several filling defects in gallbladder (arrows)
indicating adult flukes.
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Fig. 8A —67-year-old man with severe infection of Clonorchis
sinensis. Transverse MR cholangiogram shows diffuse dilatation of entire
intrahepatic bile ducts. Note filling defects (arrows) within bile
ducts due to adult flukes of C. sinensis.
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Fig. 8B —67-year-old man with severe infection of Clonorchis
sinensis. Thick-slab coronal MR cholangiogram shows diffuse severe
dilatation of peripheral intrahepatic ducts, moderate dilatation of lobar and
segmental bile ducts, and minimal dilatation of extrahepatic ducts. Although
there are many flukes in bile ducts, they are not visible because they are
very flat. Small filling defects are aggregates of adult flukes
(arrowheads). Note moderate dilatation of branch ducts of pancreas
tail due to infection in most upstream ducts of pancreas
(arrows).
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The pancreas may be involved in cases of severe infection. On endoscopic
retrograde pancreatograms or MR cholangiograms, the branch ducts in the
pancreas tail are diffusely dilated
[8] (Fig.
8A,
8B). However, the main
pancreatic duct and its tributaries in the head and body are not dilated.
Sometimes, small filling defects that might be caused by adult flukes are
observed in the main pancreatic duct.
Fascioliasis
F. hepatica is a trematode that infects cattle and sheep; humans
are accidental hosts. Infections occur due to ingestion of water or raw
aquatic plants contaminated with metacercariae, which later penetrate the
intestinal wall and migrate through the peritoneal cavity to the liver after
penetrating Glisson's capsule
[9]. Infections occur worldwide
in areas where sheep and cattle are raised, including Europe, Australia, and
other developed countries.
The flukes then track through the liver parenchyma (invasive stage) to
enter the bile ducts and gallbladder, where they mature and release eggs
(biliary stage) [9]. Mature
flukes measure 20–40 mm long and 8–12 mm wide. Hepatic
fascioliasis manifests as clusters of microabscesses arranged in a
characteristic tractlike fashion, usually in the subcapsular regions (Fig.
9A,
9B,
9C), and shows slow evolution
of the lesion on follow-up examinations
[9,
10]. A large cystlike necrotic
lesion may also be observed
[9]. On cholangiograms, biliary
fascioliasis is characterized by nonspecific biliary dilatation and single or
multiple small filling defects, which represent flukes themselves
[9] (Fig.
10A,
10B,
10C).
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Fig. 9A —63-year-old man with hepatic fascioliasis. Contrast-enhanced
transverse CT images at portal venous phase show clustered small
low-attenuating lesions with peripheral enhancement at subcapsular area of
right hepatic lobe. Note characteristic crooked tractlike lesion (burrow
tract) (arrow, B).
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Fig. 9B —63-year-old man with hepatic fascioliasis. Contrast-enhanced
transverse CT images at portal venous phase show clustered small
low-attenuating lesions with peripheral enhancement at subcapsular area of
right hepatic lobe. Note characteristic crooked tractlike lesion (burrow
tract) (arrow, B).
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Fig. 10A —32-year-old woman with biliary fascioliasis. (Reprinted with
permission from Ham SY, Park CM, Chung KB, et al. A case of fascioliasis in
common bile duct. J Korean Radiol Soc 1989; 25:783–785
[13]) Endoscopic retrograde
cholangiograms show several small elongated filling defects (arrows),
which were movable on fluoroscopy.
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Fig. 10B —32-year-old woman with biliary fascioliasis. (Reprinted with
permission from Ham SY, Park CM, Chung KB, et al. A case of fascioliasis in
common bile duct. J Korean Radiol Soc 1989; 25:783–785
[13]) Endoscopic retrograde
cholangiograms show several small elongated filling defects (arrows),
which were movable on fluoroscopy.
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Fig. 10C —32-year-old woman with biliary fascioliasis. (Reprinted with
permission from Ham SY, Park CM, Chung KB, et al. A case of fascioliasis in
common bile duct. J Korean Radiol Soc 1989; 25:783–785
[13]) Adult Fasciola
hepatica obtained from common bile duct at surgery. (scale increment = 1
mm)
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Ascariasis
The A. lumbricoides adult worm is typically 15–30 cm long
and 3–6 mm thick. Humans are permanent hosts, and infection occurs by
ingestion of eggs. After lung and tracheal migration, the worms reside in the
small intestine. A. lumbricoides is widely distributed in tropical
and subtropical regions and in other humid areas. Clinical presentations are
passage of worms through the anus or through the mouth while vomiting.
Sometimes a bolus of worms causes a small-bowel obstruction.
Occasionally, worms migrate through the ampulla of Vater into the biliary
tree and gallbladder, resulting in bile duct obstruction, cholangitis, and
pancreatitis. Sonographic findings are nonshadowing, echogenic, tubular
structures within the bile ducts, sometimes with a longitudinal central
echo-free line representing the gastrointestinal tract of the worm
[11] (Fig.
11A,
11B,
11C). Endoscopic retrograde
cholangiograms show a long tubular filling defect in the bile duct or
gallbladder [11,
12]. MR cholangiograms may
show intraductal worms as a linear low-intensity filling defect in the bile
ducts [12].
References
- Lim JH. Radiologic findings of clonorchiasis.
AJR 1990; 155:1001
–1008[Abstract/Free Full Text]
- Sripa B. Pathobiology of opisthorchiasis: an update.
Acta Trop 2003;88
: 209–220[CrossRef][Medline]
- Choi TK, Wong KP, Wong J. Cholangiographic appearance in
clonorchiasis. Br J Radiol 1984;57
: 681–684[Abstract]
- Dao AH, Barnwell SF, Adkins RB Jr. A case of opisthorchiasis
diagnosed by cholangiography and bile examination. Am
Surg 1991; 57:206
–209[Medline]
- Lim JH, Ko YT, Lee DH, Kim SY. Clonorchiasis: sonographic findings
in 59 proved cases. AJR 1989;152
: 761–764[Abstract/Free Full Text]
- Choi BI, Kim HJ, Han MC, Do YS, Han MH, Lee SH. CT findings of
clonorchiasis. AJR 1989;152
: 281–284[Abstract/Free Full Text]
- Damrongsak D, Damrongsak C, Bhothisuwan W, Chancharoensin C,
Kruatrachue C, Prabhasawat D. Computed tomography in opisthorchiasis.
Comput Radiol 1984;8
: 379–385[CrossRef][Medline]
- Lim JH, Ko YT. Clonorchiasis of the pancreas. Clin
Radiol 1990; 41:195
–198[CrossRef][Medline]
- Han JK, Choi BI, Cho JM, et al. Radiologic findings of human
fascioliasis. Abdom Imaging 1993;18
: 261–264[Medline]
- Takeyama N, Okumura N, Sakai Y, et al. Computed tomography findings
of hepatic lesions in human fascioliasis: report of two cases. Am J
Gastroenterol 1986; 81:1078
–1081[Medline]
- Kubaska SM, Chew FS. Biliary ascariasis.
AJR 1997; 169:492[Free Full Text]
- Hwang CM, Kim TK, Ha HK, Kim PN, Lee MG. Biliary ascariasis: MR
cholangiography findings in two cases. Korean J Radiol2001; 2:175
–178[Medline]
- Ham SY, Park CM, Chung KB, et al. A case of fascioliasis in common
bile duct. J Korean Radiol Soc 1989;25
: 783–785
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Abstract
Introduction
