Inferior vena cava diameter and left atrial diameter measure volume but not dry weight. Clin J Am Soc Nephrol 2011 February 17; 6(5):1066–72

Background and objectives Hypervolemia is an important and modifiable cause of hypertension. Hypertension improves with probing dry weight, but its effect on echocardiographic measures of volume is unknown. Design, setting, participants, & measurements Shortly after dialysis, echocardiograms were obtained at base-line and longitudinally every 4 weeks on two occasions. Among 100 patients in the additional ultrafiltration group, 198 echocardiograms were performed; among 50 patients in the control group, 104 echocardiograms were performed. Results Baseline inferior vena cava (IVC)insp diameter was approximately 5.1 mm/m 2; with ultrafiltration, change in IVCinsp diameter was 0.95 mm/m 2 more compared with the control group at 4 weeks and 1.18 mm/m2 more compared with the control group at 8 weeks. From baseline IVCexp diameter of ap-proximately 8.2 mm/m2, ultrafiltration-induced change at 4 weeks was 1.06 mm/m2 more and at 8 weeks was 1.07 mm/m2 more (P 0.044). From a baseline left atrial diameter of 2.1 cm/m2, ultrafiltration-in-duced change at 4 weeks was 0.14 cm/m2 more and at 8 weeks was 0.15 cm/m2 more. At baseline, there was no relationship between interdialytic ambulatory BP and echocardiographic parameters of vol-ume. The reduction in interdialytic ambulatory BP was also independent of change in the echocardio-graphic volume parameters. Conclusions The inferior vena cava and left atrial diameters are echocardiographic parameters that are re-sponsive to probing dry weight; thus, they reflect excess volume. However, echocardiographic volume pa-rameters are poor determinants of interdialytic BP, and their change does not predict the BP response to probing dry weight