The objective of the work was to evaluate the results of sonographic examination of the diameter of the vena cava inferior (VCI) as a parameter of hydratation of haemodialyzed patients. In a group of 84 haemodialyzed patients, mean age 66.32 years, the collapsibility index of the IVC was measure. The collapsibility index (CI) was calculated according to the formula: CI (%)= IVCexp - IVCinsp/IVCexp x100, where IVCexp = the maximum diameter of the IVC in maximum inspiration. Values of the index within the range from 40-75% corresponded to normal hydratation. The results were compared with ultrafiltration (total and expressed as % of body weight after haemodialyzation), „dry“ body weight and with changes of BP during haemodialysis. The mean value of CI was 63.24 ± 18.54. In 54 instances it was within the normal range (62.26 ± 11.4), in 10 it was lower (27.7 ± 6.02; possible sign of inadequate ultrafiltration during dialysis) and in 20 instances it was higher (84.9 ± 7.53; risk of excessive ultrafiltration). Clinically assessed „dry“ weight was adequate in 64 % cases. In 24 % UF was excessive. With this corresponded also the incidence of hypotension (40 %) and in these patients the „dry“ weight was subsequently elevated. The predictive importance of low values of CI for inadequate UF is how- ever not unequivocal. Some of these patients were hypotensive even in case of low UF and did not tolerate its increase.

        Key words: Haemodialysis - Ultrafiltration in haemodialysis - Optimal „dry“ weight- Vena cava inferior - Collapsability index