[Effect of gender and body mass on hemodialysis dose]. 
Dialysis efficacy affects the outcome of dialysis patient.  Increasing the dialysis dose is related with mortality decrease.  The measure of hemodialysis dose and single dialysis urea removal is expressed as Kt/V value (K is blood urea clearance, t is dialysis treatment duration, and V is volume of urea distribution).  Hemodialysis dose can be prescribed from the urea kinetic model (UKM).  Calculation of single dialysis delivered Kt/V is based on predialysis and postdialysis urea concentrations.  The aim of the study was to demonstrate the influence of body mass and gender on the delivered and prescribed dialysis dose.  Seventy-five bicarbonate low-flux hemodialysis sessions in 25 anuric subjects (13 males and 12 females) treated with chronic hemodialysis for at least one year were analyzed.  For every single hemodialysis session, delivered Kt/V (Daugirdas and Keshaviah) and prescribed Kt/V (according to UKM) were calculated.  Hemodialysis sessions in females were more efficient than in male subjects (delivered Kt/V Daugirdas 1.18 +/- 0.24 vs. *1.04 +/- 0.21, p = 0.008 and prescribed Kt/V UKM 1.42 +/- 0.16 vs. 0.92 +/- 0.11, p < 0.001).  According to body weight, hemodialysis sessions were more efficient in < 70 kg than in > 70-kg subjects (delivered Kt/V Daugirdas 1.24 +/- 0.24 vs. 1.01 +/- 0.18, p < 0.001 and prescribed Kt/V UKM 1.36 +/- 0.23 vs. 1.00 +/- 0.22, p < 0.001).  Body mass of dialyzed subject and delivered/prescribed dialysis dose showed negative correlation (r = -0.45, p < 0.001/r = -0.69, p < 0.001).  Male gender and delivered/prescribed dialysis dose also yielded negative correlation (r = -0.31, p = 0.008/r = -0.885, p < 0.001).  The results of the study demonstrated negligence in prescribing hemodialysis dose in male and heavy subjects.  Consequently, in these subjects the single delivered dialysis dose was inadequate.  We recommend careful dialysis dose prescribing and frequent measurement of the delivered dialysis dose in heavy males on chronic hemodialysis therapy.  In extreme cases, on-line monitors could be a useful tool for real time delivered dialysis dose measurement, so the prescribed dialysis parameters could be revised during the treatment (especially useful would be prolongation of the dialysis session).