Ultrafiltration and absorption in evaluating aquaporin function from peritoneal transport of sodium.
BACKGROUND
Evaluation of free water transport is a tool for assessing aquaporin function in peritoneal dialysis patients. The dialysate "sodium dip" and estimation of sieving coefficient for sodium may be used for quantification of the free water fraction in ultrafiltration flow from blood to the peritoneal cavity.


METHODS
The mini peritoneal equilibration test (mini-PET) [La Milia et al., Nephrol Dial Transplant 2002; 17(Suppl 3):17-18] is a simple method for evaluating free water transport using sodium as a marker. We compared the evaluation of free water transport using the mini-PET against detailed data on fluid and sodium transport from clinical dwell studies using a macromolecular volume marker to estimate fluid absorption and ultrafiltration rates, and the modified Babb-Randerson-Farrell model to assess the sodium transport components.


CONCLUSIONS
According to our results, the mini-PET may result in underestimation of fluid transport by about 20% because it neglects the impact of peritoneal fluid and solute absorption and sodium diffusion during the peritoneal dwell time. Nevertheless, estimation of the free water fraction in the mini-PET yields values (about 0.4) similar to the more detailed analysis.
Waniewski
Jacek
J
Institute of Biocybernetics and Biomedical Engineering, Trojdena 4, Warsaw, Poland. jacekwan@ibib.waw.pl
Debowska
Malgorzata
M
Lindholm
Bengt
B
D000042:Absorption / Q000502:physiology; D020346:Aquaporins / Q000502:physiology*; D001692:Biological Transport; D015314:Dialysis Solutions; D004058:Diffusion; D006801:Humans; D016014:Linear Models; D008954:Models, Biological; D010531:Peritoneal Dialysis, Continuous Ambulatory; D010537:Peritoneum / Q000502:physiology; D012964:Sodium / Q000378:metabolism; D014462:Ultrafiltration; D014867:Water / Q000378:metabolism
D020346:Aquaporins; D015314:Dialysis Solutions; D014867:Water; D012964:Sodium