Ultrasonographic investigation of respiratory influence on diameters of portal vessels in normal subjects.

In order to improve the basis for ultrasonographic studies of portal hypertension the normal diameters and respiratory variations in the portal vessels were measured in sixty-seven volunteers. In healthy subjects, measurements were made on the portal vein and its major tributaries. The respiratory variations were most prominent in the splenic vein, somewhat less in the superior mesenteric vein and least in the portal vein. There were no significant correlations to weight, age or height. The hypothesis that examinations performed after food intake would give more prominent respiratory variations had to be rejected but showed that the portal vein should be examined under defined conditions regarding alimentary status. The diameters alone of the portal vessels can probably not be used reliably as an indicator of portal hypertension while a respiratory variation of less than 30 per cent in the splenic vein should be considered pathologic and lead to further investigations.