An Unusual Cause of Localized Dilation of Bile Duct

Question: A 48-year-old man was found to have liver space–occupying lesions in his physical examination 4 months earlier. At that time, he did not pay attention to the situation because of his busy work. One month before this presentation, the patient went to the local hospital for evaluation. Abdominal B-ultrasound and computed tomography all indicated that liver abscess was possible. Although the patient had no clinical manifestations, such as fever and abdominal pain, and the blood routine tests and liver function tests in the laboratory evaluation were within normal ranges, the patient still received the anti-infection treatment of third-generation cephalosporin combined with morpholinenidazole for 22 days. B-ultrasound reexamination showed that the lesion was not significantly reduced. The patient was referred to our hepatology unit. Abdominal magnetic resonance imaging (MRI) showed patchy abnormal signals in the right lobe of the liver, which were considered to indicate bile duct dilation with peripheral inflammation (Figures A, B, C, and D). On physical examination, the patient was without jaundice or abdominal pain. He denied excessive alcohol consumption, smoking, or a history of gallstones. The laboratory results showed that the blood routine test, liver function test and alpha fetoprotein level were all within normal ranges. Hepatitis B and C serologies, anti–smooth muscle actin, anti–mitochondrial antibody and IgG4 subclass were unremarkable. Based on the imaging findings and the negative laboratory examinations, what is the most likely diagnosis? Look on page 535 for the answer and see the Gastroenterology website (www.gastrojournal.org) for more information on submitting to Gastro Curbside Consult. The clinical diagnosis of unexplained liver lesions is mainly based on 2 basic examinations: imaging techniques and histopathologic examinations. From the abdominal MRI features, we found that the patient had localized dilation of the tertiary bile duct in the right lobe of the liver. However, the clinical manifestations were nonspecific, lacking common manifestations of bile duct dilation such as fever, jaundice, and abdominal pain. Therefore, histopathologic examination was particularly important for etiologic diagnosis. Considering that the patient did not exclude tumor factors, he underwent partial resection of the right lobe of the liver. The pathologic specimen showed that the intrahepatic bile duct was significantly dilated irregularly and tortuously (Figures E and F). The photomicrograph (Figure G) shows many foci of nodules with egg calcification (“black matter”) and fibrosclerosis in the portal area of different sizes, some of which involve the whole portal area. We observed granuloma reaction around these calcified eggs, surrounded by a large number of fibrous tissues and a large number of lymphocytes gathered at the edge (Figure H). The morphologic characteristics of the calcified eggs were consistent with those of schistosomiasis. Further serologic testing showed positive Schistosoma japonicum antibody. But no parasites were found in stool microscopy. Patient was followed for 3 years with no history of intestinal/genitourinary or hepatic manifestations. The cause of bile duct dilation was considered to be granuloma and fibrosis in the portal area caused by schistosomiasis and finally compression of the bile duct. Schistosomiasis is a parasitic infection caused by trematode worms of the genus Schistosoma. S japonicum infection is common in China. After chronic schistosomiasis infection, the main pathologic site of the body is the liver. Adults grow and mate in the portal vein, migrate to the superior mesenteric vein, and deposit and lay eggs. The eggs reach the liver through the portal vein system, where they cause granulomatous reaction, which can lead to periportal fibrosis, leading to presinusoidal portal hypertension. Gastrointestinal, hepatosplenic, and neurologic complications are usually noted in the later stages. The diagnosis of schistosomiasis mainly depends on the identification of eggs in feces, and can also be assisted by rectal or sigmoid mucosa, or liver biopsy.1Guimarães Cavalcanti M. Marcello de Araujo-Neto J. Mauro Peralta J. Schistosomiasis: clinical management of liver disease.Clin Liver Dis (Hoboken). 2015; 6: 59-62Crossref PubMed Scopus (17) Google Scholar There are some key microscopic features of liver: for example, Schistosoma eggs, sometimes calcified, are visible in or near portal veins,2Abdelghani E. Zerpa R. Iliescu G. et al.Schistosomiasis and liver disease: learning from the past to understand the present.Clin Case Rep. 2020; 8: 1522-1526Crossref PubMed Scopus (2) Google Scholar and portal tracts may show granulomas, fibrosis, or increased vascular channels. The common imaging signs of schistosomiasis liver disease include intrahepatic calcification, central vascular shadow in portal area, calcification of portal vein wall and portal hypertension.3Manzella A. Ohtomo K. Monzawa S. et al.Schistosomiasis of the liver.Abdom Imaging. 2008; 33: 144-150Crossref PubMed Scopus (58) Google Scholar In a few patients, the intrahepatic bile ducts showed different degrees of dilation, mainly mild dilation. However, localized bile duct dilation caused by schistosomiasis is extremely rare. The objectives of therapy in schistosomiasis are to eradicate the infection in individual patients. Response to therapy is assessed primarily on the disappearance of viable eggs and improvement or resolution of hepatomegaly and periportal fibrosis. Although no viable eggs were found in the patient’s stool specimens, he still received praziquantel treatment after surgery, based on the pathologic changes of periportal fibrosis. The patient was discharged on the eighth day without any complications after surgery. At 10 months’ follow-up, he had no recurrent liver lesion and was in stable condition.