Visualization of draining vein in focal nodular hyperplasia by superb microvascular imaging: report of two cases

Focal nodular hyperplasia (FNH) is the second most common benign tumor of the liver, and diagnosis and follow-up without invasive procedures are now highly recommended. FNH shows a characteristic vascular structure called "spoke-wheel appearance". However, this appearance relies on the mode of the feeding artery, and the mode of the draining vein has not been sufficiently studied until recently. Superb microvascular imaging (SMI) is a new Doppler technology designed to improve visualization of the blood flow, especially slow flow signals from fine vessels, using a new algorithm. Thus, we can expect to see an improvement in visualization of fine vessels in FNH using SMI. Here, we present two cases in which SMI clearly demonstrated not only the typical spoke-wheel appearance but also draining to the hepatic veins. Our observation is believed to be noteworthy in the diagnosis of FNH. In conclusion, we have reported two cases of hepatic FNH in which SMI revealed clearly not only its feeding vessels and intratumoral vasculature but also its draining vessels communicating with the hepatic vein. SMI is considered to increase our diagnostic confidence by revealing fine vessels within and around the FNH lesion.