A case of hypovascular hepatic lesion with suspected clonorchiasis.

Clonorchiasis, caused by Clonorchis sinensis, is a parasitic liver disease endemic in East Asia, primarily transmitted by consuming raw or undercooked freshwater fish. While clonorchiasis is often asymptomatic, chronic infection may lead to serious complications, including cholangiocarcinoma. In Japan, the prevalence has markedly declined, yet sporadic cases persist, especially in regions with traditional dietary practices. We report a rare suspected case of hepatic clonorchiasis in a Japanese woman in her 70s. She presented with mild liver dysfunction and no overseas travel history. Routine ultrasonography revealed a 12-mm hypoechoic hepatic lesion. Further imaging studies, including contrast-enhanced ultrasound (CEUS), CT, and MRI, revealed no contrast enhancement within the lesion. Tumor markers for hepatocellular carcinoma were also negative; however, these findings were insufficient to establish a definitive diagnosis. Serologic testing revealed weakly positive clonorchiasis antibodies. A liver biopsy identified a cystic lesion with eosinophilic infiltration and necrosis, consistent with a parasitic infection. Given the patient's dietary history and serologic/pathologic evidence, clonorchiasis was considered the most likely diagnosis. This case emphasizes the diagnostic challenges of hypovascular hepatic lesions and the limitations of imaging alone. This report highlights the importance of considering parasitic infections in the differential diagnosis of hypovascular hepatic lesions, even in non-endemic settings. Ultrasonography may facilitate the early detection of liver parasites.