Heterogeneous Staining in the Liver Parenchyma After the Injection of Perflubutane Microbubble Contrast Agent

This study aimed to characterize the features of heterogeneous staining in the liver after injection of perflubutane microbubble agent (SonazoidTM, 0.0075 mL/kg). Digitized hepatic contrast sonograms from 906 subjects were reviewed to assess time-related changes in heterogeneous staining and the possible association between this effect and the clinical backgrounds was analyzed. Heterogeneous staining was found in seven subjects (0.77%) on 15-min phase sonograms. The staining initially appeared as hyper-enhanced circular spots in the liver 10 min or later after the agent injection. The number of spots increased gradually with unequally-spaced distribution. Although the staining pattern did not improve during the examination, there were no abnormal findings in vital signs or symptoms on the day and blood test results or sonograms on the following day. Heterogeneous staining is a side effect that impedes ultrasound examination. However, at present, the precise causes and underlying mechanisms of this event are unknown.