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In general, gastrointestinal tract is the primary involvement site of parasites during their life cycle. In this article, we will describe amebiasis, ascariasis,; anisakiasis among the many common intestinal parasitic diseases. We will review the epidemiology, life cycles, clinical manifestations; complications,; illustrate detailed imaging findings of intestinal parasites. Recognizing features of parasitic infection is important to establish an early diagnosis that leads to prompt treatment; helps avoid unnecessary surgery.

Mi-Suk Park1Email:radpms@yumc.yonsei.ac.kr　Ki Whang Kim1　Hyun Kwon Ha2　Dong Ho Lee3
[1] Department of Diagnostic Radiology, Institute of Gastroenterology, Research Institute of Radiological Science, Severance Hospital, Yonsei University College of Medicine, Seoul, South Korea ;[2] Department of Radiology; Research Institute of Radiology, University of Ulsan College of Medicine, Asan Medical Center, Seoul, South Korea ;[3] Department of Diagnostic Radiology, Kyung Hee University Hospital, Seoul, South Korea ;[4] Department of Diagnostic Radiology, Severance Hospital, Seodaemun-ku, Shinchon-dong 134, Seoul, 120-752, South Korea

Parasitic infection of the biliary tree is caused by liver flukes, namely Clonorchis sinensis; Opisthorchis viverrini. These flukes reside in the peripheral small bile ducts of the liver; produce chronic inflammation of the bile duct, bile duct dilatation, mechanical obstruction,; bile duct wall thickening. On imaging, peripheral small intrahepatic bile ducts are dilated, but the large bile ducts; extrahepatic bile ducts are not dilated or slightly dilated. There is no visible caused of obstruction. Sometimes, in heavy infection, adult flukes are demonstrated on sonography, CT or MR cholangiography as small intraluminal lesions. The flukes in the gallbladder may appear as floating, small objects on sonography. Chronic infection may result in cholangiocarcinoma of the liver parenchyma or along the bile ducts. Human infection of Fasciola hepatica, a cattle flukes, may occur inadvertently,; the flukes migrate in the liver (hepatic phase); reside the bile ducts (biliary phase). Image findings in the hepatic phase present with multiple, small, clustered, necrotic cavities or abscesses in the peripheral parts of the liver, showing “tunnels; caves” sign, reflecting parasite migration in the liver parenchyma. In the biliary phase, the flukes are demonstrated in the intra-; extrahepatic bile ducts; the gallbladder as small intraluminal flat objects, sometimes moving spontaneously. Bile ducts are dilated.

Jae Hoon Lim1 Email:jhlim@smc.samsung.co.kr　Eimorn Mairiang2　Geung Hwan Ahn3
[1] Department of Radiology; Center for Imaging Science, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, South Korea ;[2] Department of Radiology, Khon Kaen University Medical School, Khon Kaen, Thailand ;[3] Department of Pathology, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, South Korea

Toxocariasis is caused by dog ascarid, Toxocara canis, forming eosinophilic inflammation such as eosinophilic abscess or granuloma in the liver; lungs. The lesions move slowly; thus the disease is called as visceral larva migrans. On CT or MR imaging, hepatic lesions are seen as multiple, ill-defined, oval lesions that measure 1.0–1.5 cm in diameter. Sometimes, the lesion may be angular or trapezoid. The lesions are usually best seen on the portal venous phase in dynamic contrast-enhanced CT; MR imaging; the lesions are either not seen or only faintly seen on arterial; equilibrium phases. Either an enhancing rim or enhancing nodules are sometimes observed. On sonography, the lesions appear as multiple, small, oval hypoechoic lesions in the liver parenchyma. The lesions differ from metastatic nodules is as much as they have fuzzy margins, are uniform in size, non-spherical shape; are best seen on portal venous phase. On follow-up imaging, the lesions may improve, or sometimes a change positions, reflecting migration of larva in the liver, supporting the phenomenon of visceral larva migrans.

Jae Hoon Lim1 Email:jhlim@smc.samsung.co.kr
[1] Department of Radiology; Center for Imaging Science, Samsung Medical Center, Sungkyunkwan University School of Medicine, 50 Ilwon-dong Kangnam-ku, Seoul, 135-710, South Korea

Parasitic diseases of the liver; biliary tract include echinococcosis, schistosomiasis, toxocariasis, clonorchiasis,; opisthorchiasis, affecting millions people in some endemic areas. Amebiasis; ascariasis are believed to be the most common bowel lumen indwelling parasitic diseases, affecting billions people worldwide, but sometimes these parasites migrate inadvertently to the liver; biliary tract, resulting in liver abscess or obstructive jaundice. Imaging findings of these parasitic diseases are fairly characteristic; easy to recognize if radiologists are aware of the findings, especially in endemic areas. Because of increased immigration; frequent travelling, some patients with “exotic” parasitic diseases may be encountered in non-endemic areas,; the diagnosis may be delayed or difficult,; it is often made only after operation. This feature section was designed to provide the detailed imaging features of common parasitic diseases affecting the abdominal organs; peritoneal cavity, based on pathology-image correlation.

Jae Hoon Lim1 Email:jhlim@smc.samsung.co.kr
[1] Department of Radiology; Center for Imaging Science, Samsung Medical Center, Sungkyunkwan University School of Medicine, 50 Ilwon-dong, Kangnam-ku, Seoul, 135-710, South Korea

Schistosomiasis is an infection of trematodes, Schistosoma, causing periportal fibrosis; liver cirrhosis due to deposition of eggs in the small portal venules. In schistosomiasis caused by S. mansoni, sonography shows echogenic thickening or fibrotic band along the portal veins. CT shows low-attenuation bands or rings around the large portal vein branches in the central part of the liver with marked enhancement. Hepatoplenomegaly, liver cirrhosis, portal hypertension; gastroesophageal varies are commonly associated. In schistosomiasis caused by S. japonicum, sonography shows echogenic septae in the liver, utlining the polygonal liver lobules, mimicking “fish-scale” network appearance, reflecting fibrosis. CT shows periportal septae in the peripheral part of the liver parenchyma, producing “turtle-back” appearance, representing calcified eggs along the portal tracts. The portal tracts; hepatic capsule are enhanced on contrast-enhanced CT images. The size; shape of the liver are relatively preserved. MR images show fibrous septae as low signal intensity on T1-weighted images, high signal intensity on T2-weighted images,; these fibrous septae are enhanced. CT images of the lungs show multiple scattered nodules with halo of ground-glass opacities. Exudative granulomatous inflammation of the colonic wall may produce inflammatory polyps, fibrous thickening or stenosis of the colonic wall.

Adonis Manzella1　Kuni Ohtomo2　Shuichi Monzawa3　Jae Hoon Lim4 Email:jhlim@smc.samsung.co.kr
[1] Department of Radiology, Hospital das Clinicas, Universidade Federal de Pernambuco in Recife, Recife, Brazil ;[2] Department of Radiology, University of Tokyo School of Medicine, Tokyo, Japan ;[3] Department of Radiology, Akashi Municipal Hospital, Hyogo, Japan ;[4] Department of Radiology; Center for Imaging Science, Samsung Medical Center, Sungkyunkwan University School of Medicine, 50 Ilwon-dong, Kangnam-ku, Seoul , 135-710, South Korea

Echinococcosis, also known as hydatid disease, is an infection of larval stage animal tapeworm, Echinococcus. The larvae reside in the liver; lungs, producing multiloculated fluid-filled cysts. Imaging findings of Echinococcosis caused by E. granulosus are single, unilocular cyst or multiseptated cysts, showing “wheel-like”, “rosette-like” or “honeycomb-like” appearances. There may be “snow-flakes” sign, reflecting free floating protoscoleces (hydatid-sand) within the cyst cavity. Degenerating cysts show wavy or serpentine bands or floating membranes representing detached or ruptured membranes. Degenerated cysts show heterogeneous, solid-looking pseudotumor that may show “ball of wool sign”. Dead cysts show calcified cyst wall. Echinococcosis caused by E. multilocularis produces multilocular alveolar cysts with exogeneous proliferation, progressively invading the liver parenchyma; other tissues of the body. Imaging findings are ill-defined infiltrating lesions of the liver parenchyma, consisting of multiple small clustered cystic; solid components. On sonography, lesions are heterogeneous with indistinct margins, showing “hailstorm appearance” or “vesicular or alveolar appearance”. CT; MR imaging displays multiple, irregular, ill-defined lesions. Multiple small round cysts with solid components are frequent. Large lesions show “geographical map” appearance. Calcifications are very frequent, appearing as peripheral calcification or punctuate scattered calcific foci. Invasion into the bile ducts, portal vein or hepatic vein may occur. Direct spread of infected tissue may result in cysts in the peritoneal cavity, kidneys, adrenal gland or bones.

Benedikt V. Czermak1　Okan Akhan2　Renate Hiemetzberger3　Bettina Zelger4　Wolfgang Vogel5　Werner Jaschke1　Michael Rieger1　Sang Yoon Kim6　Jae Hoon Lim7 Email:jhlim@smc.samsung.co.kr
[1] Department of Radiology, Medical University Innsbruck, Innsbruck, Austria ;[2] Department of Radiology, Hacettepe University School of Medicine, Sihhiye, Ankara, Turkey ;[3] Department of Cardiology, Medical University Innsbruck, Innsbruck, Austria ;[4] Department of Pathology, Medical University, Innsbruck, Austria ;[5] Department of Gastroenterology, Medical University Innsbruck, Innsbruck, Austria ;[6] Department of Pathology, Kon Kuk University, School of Medicine, Choongju, South Korea ;[7] Department of Radiology; Center for Imaging Science, Samsung Medical Center, Sungkyunkwan University School of Medicine, 50 Ilwon-dong, Kangnam-ku, Seoul, 135-710, South Korea

There are many causative diseases to produced portal vein thrombosis (PVT) with the most common being liver cirrhosis with hepatocellular carcinoma. Visualization of abnormalities associated with PVT is crucial to diagnosis and appropriate intervention. Dynamic contrast enhanced CT is the best means of diagnosis of PVT and evaluation of various causative diseases. The findings of PVT of the dynamic CT are filling defect partially or totally occluding the vessel lumen and rim enhancement of the vessel wall. Signs and symptoms of PVT may be subtle or nonspecific and overshadowed by the underlying illness. Radiologists should be aware of the clinical situations that predispose a patient to portal or mesenteric vein thrombosis.

Lee HK　Park SJ　Yi BH　Yeon EK　Kim JH　Hong HS
Department of Radiology, Soonchunhyang University, Bucheon Hospital, 1174 Jung-Dong Wonmi-Gu, Bucheon-Shi Kyungki-Do, South Korea. hklee@schbc.ac.kr