Frequency and Causes of Discrepancy between Kt/V and Creatinine Clearance

Abstract

Objective This study examines the frequency of discrepancy between Kt/V urea and creatinine clearance (Ccr) measurements in patients on peritoneal dialysis (PD) and the reasons for this discrepancy. Design Nonrandomized, retrospective data analysis. Setting Single PD unit of a university teaching hospital. Patients All adult patients receiving PD at our center from January 1995 to December 1996. Methods Actual (a) and desired (d) body weight (BW) were used to calculate urea volume of distribution (V) and body surface area (BSA). Patients were divided into four groups based upon their total small solute clearances (Kt/V and Ccr, normalized by actual weight) and three additional groups based upon actual/desired (a/d) body weight ratio. An additional analysis was performed for the subset of anuric patients. Data collected for all patients included the following: total Kt, total Ccr, 4-hour dialysate/ plasma (D/P) creatinine, serum albumin concentration, duration of PD, actual body weight, age, and height. Results Twenty-three percent of the clearance measurements in our study were discrepant, defined as having values for either Kt/V or Ccr (but not both) above the accepted targets of Kt/V ≥ 2.0/wk and Ccr ≥ 60 L/wk/ 1.73 m2. Patients with both values above target are more likely to have higher residual renal function. Patients who are significantly less than BWd and patients on PD for a longer time are more likely to have adequate Kt/V but not Ccr. Furthermore, patients who are less than 90% or greater than 110% of BWd have markedly different values for Kt/V and Ccr when BWa versus BWd values are used. Conclusions Kt/V and Ccr values are frequently discrepant; a number of factors affect these two measurements to varying degrees, including weight, degree of residual renal function, and duration of PD.

Peritoneal urea and creatinine clearances in continuous peritoneal dialysis patients with different types of peritoneal solute transport

“…The physiological causes of these discrepancies are residual renal function and peritoneal solute transport type: Subjects with substantial residual renal function and adequate C pr N cr may be at risk for low K pr t/V ur ; those with low or even low-average transport and adequate K pr t/V ur may be at risk for low C pr N cr [8,10]. A preliminary report suggested that the discrepancy between the two clearances is more frequent, around 30%, when the recent weekly targets of 2.0 for K pr t/V ur and 60 liters for C pr N cr are tested [11].…”

The Relationship Between Serum Folate Level and Residual Renal Function in CAPD Patients

“…A previous retrospective study found that the results of Kt/V and Ccr dialysis were contradictory in nearly 23% of PD patients, and further analysis suggested that the reason may have been related to the role of renal filtration and reabsorption. 27 The creatinine produced during human metabolism is excreted mainly through glomerular filtration and renal tubular secretion, while urea can be partially reabsorbed by renal tubules after glomerular filtration, which causes a discrepancy in the statistical analysis results between assessments of Kt/V and Ccr.…”

Optimal Timing of Hemodialysis Before Surgery

“…However, hemodialysis-free weekend days are associated with increased fluid and electrolyte retention that likely increase the risk of cardiac death. An analysis of United States Renal Data System data revealed that 20.2% of cardiac deaths (vs 14.3% expected, P = .0005) occurred on Monday for patients undergoing hemodialysis on a Monday, Wednesday, and Friday schedule. Similar findings regarding the rates of cardiac death were observed on Tuesdays for patients undergoing hemodialysis on a Tuesday, Thursday, and Saturday schedule.…”