Clinical studies on inferior right hepatic veins

Many small veins are called accessory, short hepatic veins in addition to the right, middle and left hepatic veins. The size of these veins varied from a pinhole to 1 cm; the size of inferior right hepatic veins (IRHVs) is thicker than that of short hepatic veins or more than 1 cm occasionally. Adults have a higher incidence rate of the IRHV.

A literature search of the PubMed database was conducted and research articles were reviewed.

The size of IRHVs is related to the size of the right hepatic vein, i.e. the larger the diameter of the right hepatic vein, the smaller the diameter of the IRHVs, and vice versa. The IRHVs are divided into superior, medial and inferior groups, separately named the superior, medial and inferior right hepatic veins according to the position of the IRHV entering the inferior vena cava. The superior right hepatic vein mainly drains the superior part of segment VII, and the medial right hepatic vein drains the middle part of segment VII. A thicker IRHV mainly drains segment VI and the inferior part of segment VII and a thinner IRHV drains the inferior part of segment V.

The clinical significance of these studies on IRHVs is varied: (1) Hepatic caudate lobe resection could be introduced after study on the veins of that lobe. (2) It is very important to identify the draining region of the IRHV for guiding hepatic segmentectomy. The postero-inferior area of the right lobe can be preserved along with the hypertrophic IRHV even if the entire main right hepatic vein is resected during segmentectomy of VII and VIII with right hepatic vein resection for patients with primary liver cancer. (3) The ligation of the major hepatic vein for the treatment of juxtahepatic vein injury is recommended because of severe hemorrhagic shock and difficulty in exposure. (4) It is very helpful to decide therapeutic modalities for Budd-Chiari syndrome.