Hepatopulmonary syndrome with large pulmonary arteriovenous malformations: CT findings with emphasis on its association with a mosaic pattern of the lung parenchyma.

We present a case of a 54-year-old patient with cirrhosis, progressive dyspnea, and platypnea. Thoracic computed tomography (CT) showed multiple pulmonary arteriovenous malformations (PAVM), confirming the diagnosis of hepatopulmonary syndrome (HPS). Besides precisely identifying the number and location of PAVM, CT also demonstrated a striking mosaic pattern of the lung parenchyma, characterized by the presence of alternating geographic areas of low attenuation (showing pulmonary vessels with a decreased diameter) with regions of relatively increased attenuation (showing pulmonary vessels with a normal diameter). This mosaic pattern of the lung parenchyma has scarcely been described in patients with HPS since it is not always present and usually requires a post-processing of the CT images in order to increase the contrast between the low attenuation areas (representing hypoperfused regions) and the areas with a relatively increased attenuation (representing better perfused regions). The decision was made to embolize the major PAVM, achieving an improvement of both the oxygen partial pressure and the patient's symptoms. This improvement allowed the patient to become an acceptable candidate for liver transplantation. We believe that, unlike other radiological signs of HPS, the mosaic pattern has not been sufficiently described in the scientific literature. If the association of the mosaic pattern on CT with HPS is confirmed in larger studies, it could become a useful sign for detecting hypoperfused pulmonary areas related to small nonvisible PAVM.