Abbreviated Method for Urea Kinetic Modeling in Continuous Ambulatory Peritoneal Dialysis Patients

Urea kinetic modeling (UKM) is an established method for quantitating hemodialysis, with target values clearly defined. Precise methods for measuring continuous ambulatory peritoneal dialysis (CAPD) prescriptions are less well-defined, and 24-hour collections of dialysate effluent are logistically impractical.

UKM parameters derived from an abbreviated (4-hour) collection period were compared with simultaneously obtained 24hour collections of urine and dialysate effluent in 22 CAPD patients. Daily Kt/V was calculated from total (residual renal and peritoneal) urea clearance and an anthropometric-derived total body water volume. Results yielded from the 24-hour collection included a mean Kt/V of 0.29±0.09, and mean protein catabolic rate (PCR) of 0.84±0.24 g/kg/day. Daily Kt/V values were calculated from each individual dialysate cycle. The first morning cycle after an overnight dwell correlated best with results obtained using 24-hour collections (r=0.921; p<0.0001) with no significant differences in Kt/V found (p=0.454) between the short and 24-hour methods. Daily Kt/V values converted by exponential transformation to a thrice-weekly hemodialysis value yielded a Kt/V equivalent of 1.02±0.40.

UKM using an abbreviated collection period is an accurate and practical tool for quantitating CAPD adequacy in a routine clinical setting.