The authors describe a decrease of serum cystatin C on the hrst postoperative day (hysterectomy). There was no relationship between the decrease of cystatin C and weight of extracted tissue, blond loss, changes in serum urea or serum creatinine. As the intraindividual variability of cystatin C is higher than intraindividual variability of creatinine fit is necessary to take shon physiological or pathological changes finto account and re-evaluate conditions for the estimation of intraindividual variability of cystatin C.

        Key words: cystatin C, critical care, operative stress, intraindividual variability.