[Development on segmentectomy and subsegmentectomy of the liver due to introduction of ultrasonography].

Due to introduction of preoperative and intraoperative ultrasound into liver surgery, three dimensional structure of the liver is understood much better than before. Intraoperative sonography demonstrated many daughter nodules and tumor thrombi which were not detected preoperatively. Therefore, a part of noncurative resection of the liver can be avoided. In patients with liver cirrhosis and small hepatoma, 60 per cent of hepatomas could not be visible nor palpable from the surface of the liver. In these patients, if hepatic lobectomy is performed, liver dysfunction will develop after surgery. Therefore, small partial resection is indicated and identification of site of the tumor is indispensable. With intraoperative sonography, all invisible and nonpalpable tumors in the liver were demonstrated. Clinicopathological studies of the hepatocellular carcinoma suggest that the tumor cells spread in the liver through the portal venous branches even in the small hepatocellular carcinoma. Daughter nodules will grow in the distal region of the portal venous branch. Therefore, total resection of the subsegment which contains the tumor is indicated. For this purpose, systematic subsegmentectomy is considered. In this operation, portal area containing tumor is identified by ultrasonically guided puncture of the portal venous branch. By identification of the inferior right hepatic vein, the right postero-inferior area can be preserved, even if right hepatic vein is resected. This type of hepatectomy is called inferior right hepatic vein preserving operation. We already performed this operation in three patients.