The inferior vena cava diameter as a marker of dry weight in chronic hemodialyzed patients.

We have previously reported that the diameter of the inferior vena cava (IVC) reflects the amount of body fluid in hemodialyzed (HD) patients. The present study was undertaken to depict the criteria of IVC diameters for determining dry weight (DW) in anuric HD patients. In healthy subjects, the maximal diameters during quiet expiration (IVCe) and the minimal diameters during quiet inspiration (IVCi) were 16.7 +/- 3.2 and 5.7 +/- 5.4 mm, respectively (mean +/- SD). The collapsibility index (CI, 1 - IVCi/IVCe), which inversely correlates with the central venous pressure, was 0.68 +/- 0.29. In anuric HD patients, the IVCe/CI values before and after HD were 14.9 +/- 3.2/0.68 +/- 0.24 and 8.2 +/- 2.3/0.94 +/- 0.09, respectively. IVCe decreased proportionally to the amount of ultrafiltration. In HD patients with hypervolemic pulmonary edema, the IVCe and CI values were 22.4 +/- 2.9 and 0.22 +/- 0.11, respectively. We proposed that IVCe/CI after HD is 8 +/- 3 mm/0.9 +/- 0.1 as the markers of DW in anuric HD patients and that an IVCe value > or = 22 mm together with a CI < or = 0.22 implies the warning level of body fluid retention.