Intravascular ultrasound of the portal vein--normal anatomy.

The purpose of this study was to evaluate the appearance of the normal portal vein with intravascular ultrasound. The portal vein was studied in 10 patients with colorectal carcinoma without known liver or pancreatic disease. For the intravascular portovenous examination, a 2.0-mm, 20-MHz ultrasound catheter was used. The field of view was 30 mm. The wall of the portal vein appeared as a single hyperechoic layer 0.5 to 0.8 mm in thickness. Normal structures adjacent to the portal vein, such as the common bile duct, the hepatic artery or small lymph nodes, were clearly separated from the lumen of the portal vein by the wall of the vein together with some periportal fat. In most cases the parenchyma of the pancreas could be separated from the wall of the vein.