Adequacy of peritoneal dialysis: Kt/V revisited

Kt/V urea has been used to assess adequacy of peritoneal dialysis. However, Kt/V urea only reflects the clearance of solute without taking into consideration the effects of dietary protein intake (DPI). The objective of this study is to evaluate the value of Kt/V based on nitrogen balance and to observe if it is the best adequacy index.

On the premise that nitrogen balance is obtained, we calculated the minimal adequate dialysate volume and dialysis index (DI), Kt/V and solute removal index (SRI). We compared the values of DI, Kt/V and SRI to evaluate the adequacy of peritoneal dialysis.

Kt/V was changed with DPI and body weight of continuous ambulatory peritoneal dialysis (CAPD) patients. We cannot define adequate dialysis with a single value while DPI and body weight are different since CAPD, SRI and Kt/V are numerically equal. However, dialysis index (DI) can reflect the minimal adequate dialysate volume when DPI and body weight are different and, thus, reflects the adequacy of dialysis.

DI reflects the balance between DPI and solute clearance; thus, it is more useful to evaluate dialysis adequacy than Kt/V and SRI in clinically stable peritoneal dialysis patients.