[How much body water volume affects evaluation of urea clearance in patients treated with peritoneal dialysis?].
OBJECTIVE
Peritoneal dialysis adequacy is usually estimated using the ratio of total weekly urea clearance (Kt) and urea distribution volume (V), the later being identical to total body water volume. It is observed that even patients with acceptable Kt/V values sometimes show signs and symptoms of dialysis inadequacy. A question arose whether the discrepancy came from a falsely assessed urea distribution volume, because the less the urea distribution volume measured the higher the Kt/V gained.


METHODS
The survey included 32 patients (15 women, 17 men) in whom 62 total weekly urea clearances were calculated during a 2-year period. Each Kt was used in 4 different equations (A-Watson's method, B-Hume's method, C-58% of body mass for urea distribution volume, D-for urea distribution volume: 58% of body mass reduced by 2 kg, and then augmented by 2 kg added for dialysate volume assumed). It resulted in 4 different Kt/V for each Kt, i.e. a total of 248 Kt/V values.


CONCLUSIONS
At the moment of the examination the patients were aged 57.66 +/- 8.66 years, weighted 75.54 +/- 11.04 kg (with dialysate intraperitoneally), and were treated with peritoneal dialysis for a mean of 23.28 +/- 27.55 months. Their mean total weekly urea clearance was 79.94 +/- 12.53 L. Depending on the method used, the mean urea distribution volumes were as follows: A = 37.24 +/- 5.27 L, B = 37.89 +/- 5.22 L, C = 43.81 +/- 6.40 L and D = 44.65 +/- 6.47 L, and mean Kt/V 2.15 +/- 0.32 (A), 2.11 +/- 0.32 (B), 1.82 +/- 0.33 (C) and 1.79 +/- 0.34 (D). The highest mean urea distribution volume (D) was higher than the lowest value (A) by 19.90%, and the difference between those values was statistically significant (tV D: A = 6.99, p < 0.01). The highest mean total weekly Kt/V (A) was higher than the lowest value (D) by 20.11%, and the difference was also significant ((tKt/V A: D = 6.08, p < 0.01).


CONCLUSIONS
The estimation of urea distribution volume has a direct impact on calculation results of total weekly Kt/V in peritoneal dialysis patients. Urea distribution volumes as assessed by the anthropometrical methods or by a certain percentage of body mass were approximate values. We suggest replacing "nondeuterial methods" by deuterial, in order to get more comparable results.
Jakić
Marko
M
Odjel za dijalizu Klinika za unutarnje bolesti Klinicka bolnica Osijek 31000 Osijek, Hrvatska.
Mihaljević
Dubravka
D
Zibar
Lada
L
D001834:Body Water; D001835:Body Weight; D003404:Creatinine / Q000378:metabolism; D005260:Female; D006801:Humans; D007676:Kidney Failure, Chronic / Q000503:physiopathology / Q000628:therapy; D008297:Male; D010531:Peritoneal Dialysis, Continuous Ambulatory; D010537:Peritoneum / Q000378:metabolism*; D014508:Urea / Q000378:metabolism*
D014508:Urea; D003404:Creatinine