Change in inferior vena caval diameter detected by ultrasonography during and after hemodialysis.

The diameter of the inferior vena cava (IVC) measured by ultrasonography is used as a parameter to estimate right sided cardiac function and central venous pressure. In the current study the IVC diameter during and after hemodialysis (HD) was measured in chronic HD patients to explore the determinant factors of the diameter, and these results were obtained: 1) the maximal diameter of the IVC during quiet expiration (IVCe) can be a marker of circulating blood volume during as well as after HD, because the linear correlation between IVCe and circulating blood volume during and after HD were significant and almost identical; 2) the amount of ultrafiltration is the major determinant of IVCe during HD, because IVCe and circulating blood volume decreased in parallel with the amount of ultrafiltration during HD; and 3) since the recovery of IVCe and circulating blood volume, which correlated with the increase in serum protein concentration during HD, was almost complete while the body weight remained unchanged after HD, plasma refilling rather than body fluid retention was considered important in the recovery of IVCe and circulating blood volume after HD.