Nutrition Indices in Obese Continuous Peritoneal Dialysis Patients with Inadequate and Adequate Urea Clearance

♦ Objective

To test whether better nutrition is associated more with adequate urea clearance than with inadequate urea clearance in obese patients on continuous peritoneal dialysis (CPD).

♦ Design

Retrospective analysis of clearance and nutrition indices in obese CPD patients. Only obese patients were analyzed. Obesity was defined as a ratio of actual weight to desired weight (W/DW) ≥ 1.2. The dose of dialysis was considered adequate at weekly Kt/V urea ≥ 2.0. Small solute clearances and nutrition indices were compared between patients with weekly Kt/V urea < 2.0 and patients with weekly Kt/V urea ≥ 2.0 at the first clearance study.

♦ Setting

Four university-affiliated and two private dialysis units in Canada and the United States.

♦ Patients

A total of 270 CPD patients with W/DW ≥ 1.2 at the first clearance study.

♦ Results

Among the 270 obese CPD patients, 157 (58.1%) were underdialyzed (weekly Kt/V urea 1.66 ± 0.22) and 113 (41.9%) had adequate dialysis (weekly Kt/V urea 2.51 ± 0.47) at the first clearance study. Creatinine clearance values also differed between the underdialyzed and adequately dialyzed obese groups (55.6 ± 15.2 vs 87.6 ± 29.8 L/1.73 m2 weekly, respectively, p < 0.001). The underdialyzed group contained fewer women (39.5% vs 60.2%, p < 0.001) and more patients with anuria (35.0% vs 8.8%, p < 0.001), and had higher serum urea (20.7 ± 6.9 vs 18.2 ± 5.3 mmol/L, p = 0.001) and serum creatinine (974 ± 283 vs 734 ± 275 μmol/L, p < 0.001), marginally lower serum albumin (35.8 ± 5.2 vs 37.2 ± 6.4 g/L, p = 0.082), lower urea nitrogen excretion (5778 ± 2290 vs 7085 ± 2238 mg/24 hr, p < 0.001) and indices derived from urea nitrogen excretion (protein nitrogen appearance and normalized protein nitrogen appearance), and lower creatinine excretion (1034 ± 349 vs 1217 ± 432 mg/24 hr, p < 0.001) and indices derived from creatinine excretion (lean body mass normalized to actual or desired weight) than the adequately dialyzed group.

♦ Conclusion

Nutrition indices derived from urea nitrogen and creatinine excretion are worse in underdialyzed than in adequately dialyzed obese CPD patients. This finding may have clinical importance, despite the mathematical coupling between small solute clearances and excretion rates in cross-sectional studies, because of evidence from other studies that small solute excretion rate in cross-sectional studies is a robust independent predictor of outcome in CPD.

Increasing the Dialysis Volume and Frequency in a Fixed Period of Time in CPD Patients: The Effect on Kpt/V and Creatinine Clearance

Background

The National Kidney Foundation Kidney Disease Outcomes Quality Initiative (K/DOQI) has evidence- and opinion-based recommendations for weekly Kt/Vurea and weekly total creatinine clearance (CC) in chronic peritoneal dialysis (CPD) patients. Using standard continuous ambulatory peritoneal dialysis technique, it is often difficult to achieve the suggested targets in anuric patients with large body mass. Thus, the use of automated peritoneal dialysis (APD) has been increasingly utilized to achieve adequate clearances. Automated dialysis is usually performed at night over an 8- to 10-hour period. The role of increases in dialysate volume and frequency of exchanges during this time period to achieve these target K/DOQI recommendations remains uncertain. We decided to study the effects of increasing the volume and number of exchanges in a fixed period of time in CPD patients.

Methods

In the New Haven CAPD unit, 29 patients maintained on APD were considered eligible for the study and 11 agreed to participate. The patients were characterized according to standard peritoneal equilibration test criteria. The patients were placed into two groups: group 1 included high (H) and high-average (HA), and group 2 low-average (LA) transporters. The patients were dialyzed at night for 9 hours with standard cycling technique, using 2.5% Dianeal (Baxter Healthcare, Deerfield, Illinois, USA) solution, with a cycle volume of 2500 mL, and a 2000-mL daytime dwell. Three studies were done on each patient using a total dialysis volume of 9.5 L (3 cycles), 14.5 L (5 cycles), and 19.5 L (7 cycles). Daily Kpt/Vurea and daily CCp (peritoneal) (L/day/1.73 m2) were obtained.

Results

Six patients were H or HA (group 1) and 5 were LA transporters (group 2). For the group 1 patients, mean weight was 86.6 ± 13.5 kg; Kpt/Vurea was 1.68 ± 0.21 using 9.5 L, 2.03 ± 0.28 for 14.5 L ( p < 0.05 compared to 10 L), and 2.28 ± 0.28 with 19.5 L ( p < 0.05 compared to 10 L and 15 L); mean weekly CCp was 45.43 ± 7.63 L/1.73 m2 for 9.5 L ( p < 0.05 compared to 14.5 L and 19.5 L), 51.17 ± 7.07 with 14.5 L, and 54.67 ± 10.08 for 19.5 L; ultrafiltration rates were not different in the three studies. For the group 2 patients, mean weight was 74.3 ± 17.7 kg; mean weekly Kpt/Vurea was 1.68 ± 0.35 using 9.5 L, 2.10 ± 0.42 for 14.5 L ( p < 0.05 compared to 9.5 L), and 2.31 ± 0.56 for 19.5 L ( p < 0.05 compared to 9.5 L and 14.5 L); mean weekly CCp was 42.56 ± 10.64 L/1.73 m2 for 9.5 L ( p < 0.05 compared to 14.5 L and 19.5 L), 50.89 ± 12.66 for 14.5 L, and 51.94 ± 11.20 for 19.5 L; ultrafiltration was lower in the 9.5-L study than in the 14.5-L and 19.5-L studies, but was not different in the 14.5-L and 19.5-L studies.

Conclusions

In both H/HA and LA transporters, Kpt/Vurea and CCp rise significantly when the frequency of exchanges and total volume of dialysate are increased. Thus, the use of larger volumes of dialysate with cycling peritoneal dialysis may result in increased clearances of urea and creatinine.

24-Hour Dialysate Collection for Determination of Peritoneal Membrane Transport Characteristics: Longitudinal Follow-Up Data for the Dialysis Adequacy and Transport Test (Datt)

Objective

To determine the ability of the dialysis adequacy and transport test (DATT) to monitor changes in peritoneal transport characteristics over time.

Setting

University-based peritoneal dialysis program.

Patients

One hundred patients on continuous ambulatory peritoneal dialysis who underwent 226 simultaneous DATTs and peritoneal equilibration tests (PET).

Methods

Retrospective analysis of DA TT and PET data.

Results

The mean 24-hour dialysate-to-plasma creatinine (cr) concentration ratio (DIP cr) from the DATT was 0.70±0.10, and the mean four-hour DIP crfrorn the PET was 0.68 ± 0.10. The correlation coefficient between the fourhour and 24-hour DIP cr was 0.81, and the standard error of estimate was 0.065. The mean (±SD) difference between the four-hour and 24-hour DIP cr was 0.023 ± 0.061. Fifty eight patients had two or more sequential DA TTs and PETs. For these 94sets of sequential DATTs and PETs, the mean (±SD) difference between the change in the four-hour DIP cr and the change in the 24-hour DIP cr was 0.020 ± 0.024, and the standard error of estimate was 0.064. In 17 patients a change in dwell volume from 2.0 L to 2.5 L occurred between the first and second measures of peritoneal membrane transport characteristics. The mean (±SD) difference between the change in the four-hour DIP cr and the change in the 24-hour DIP cr was 0.036 ± 0.055, and the standard error of estimate was 0.087.

Conclusion

The DATT can be used to monitor for changes in peritoneal transport over time. It should not be used in patients receiving cycler therapy or in patients whose dwell times and dextrose concentrations vary markedly from day to day.

Survival of functionally anuric patients on automated peritoneal dialysis: the European APD Outcome Study

The European APD Outcome Study (EAPOS) is a 2-yr, prospective, multicenter study of the feasibility and clinical outcomes of automated peritoneal dialysis (APD) in anuric patients. A total of 177 patients were enrolled with a median age of 54 yr (range, 21 to 91 yr). Previous median total time on dialysis was 38 mo (range, 1.6 to 259 mo), and 36% of patients had previously been on hemodialysis for >90 d. Diabetes and cardiovascular disease were present in 17% and 46% of patients, respectively. The APD prescription was adjusted at physician discretion to aim for creatinine clearance (Ccrea) >/=60 L/wk per 1.73 m(2) and ultrafiltration (UF) >/=750 ml/24 h during the first 6 mo. Baseline solute transport status (D/P) was determined by peritoneal equilibration test. At 1 yr, 78% and 74% achieved Ccrea and UF targets, respectively; median drained dialysate volume was 16.2 L/24 h with 50% of patients using icodextrin. Baseline D/P was not related to UF achieved at 1 yr. At 2 yr, patient survival was 78% and technique survival was 62%. Baseline predictors of poor survival were age (>65 yr; P = 0.006), nutritional status (Subjective Global Assessment grade C; P = 0.009), diabetic status (P = 0.008), and UF (<750 ml/24 h; P = 0.047). Time-averaged analyses showed that age, Subjective Global Assessment grade C and diabetic status predicted patient survival with UF the next most significant variable (risk ratio, 0.5/L per d; P = 0.097). Baseline Ccrea, time-averaged Ccrea, and baseline D/P had no effect on patient or technique survival. This study shows that anuric patients can successfully use APD. Baseline UF, not Ccrea or membrane permeability, is associated with patient survival.

Response to inadequate dialysis in chronic peritoneal dialysis patients. Results from the 2000 Centers for Medicare and Medicaid (CMS) ESRD Peritoneal Dialysis Clinical Performance Measures (PD-CPM) Project

BACKGROUND

It is not known if patient prescriptions are being changed if patients are receiving an inadequate dose of peritoneal dialysis.

METHODS

Data from the 2000 Centers for Medicare and Medicaid were used to obtain data on dialysis adequacy and dialysis prescriptions.

RESULTS

A total of 359 of 1,268 (28%) adult peritoneal dialysis patients had a total weekly Kt/V urea (twKt/V) less than 2.0 and 436 of 1,245 (35%) patients had a total weekly creatinine clearance (twCrCl) less than 60 L/wk/1.73 m2, defined as "inadequate dialysis." Among chronic ambulatory peritoneal dialysis (CAPD) patients, 81 of 188 (43%) patients had inadequate dialysis and a change in the peritoneal dialysis prescription within 6 months of the initial adequacy value. Among cycler patients, 106 of 197 (54%) patients had inadequate dialysis and a change in the prescription. Thirty-six of 46 (78%) CAPD patients and 48 of 56 (86%) cycler patients had an improvement in twKt/V after the prescription was revised. Thirty-two of 42 (76%) CAPD patients and 45 of 57 (79%) cycler patients had an improvement in twCrCl after the prescription was changed. For these patients, twKt/V increased from 1.6 +/- 0.3 to 2.1 +/- 0.5, with an increase in the peritoneal Kt/V urea from 1.5 +/- 0.3 to 1.9 +/- 0.4. Similarly, twCrCl increased from 46.3 +/- 7.5 to 59.1 +/- 10.6 L/wk/1.73 m2 with an increase in the peritoneal CrCl dose from 42.0 +/- 9.1 to 52.7 +/- 9.9 L/wk/1.73 m2.

CONCLUSION

About half of peritoneal dialysis patients with inadequate dialysis did not have a prescription change and could benefit from modifications in their dialysis prescription.

Urea kinetic analysis of automated peritoneal dialysis allows calculation of a CAPD-equivalent Kt/V(urea)

BACKGROUND

Based on evidence of increased mortality with decreasing urea clearance, the Dialysis Outcomes Quality Initiative (DOQI) recommended a weekly Kt/Vurea of 2.0 or higher for patients receiving continuous ambulatory peritoneal dialysis (CAPD). DOQI recommendations for automated peritoneal dialysis (APD) are based on efforts to determine the clearance providing urea mass removal equivalent to CAPD. We have adapted a variable volume direct quantitation urea kinetic model (UKM) in an effort to assess DOQI APD guidelines.

METHODS

The daily urea mass removed with a weekly Kt/Vurea of 2.0 was calculated using standardized CAPD patient profiles. Using this value and defining the pre-APD plasma urea nitrogen (PUN) as C0 and equal to the CAPD steady-state PUN, the UKM reiteratively calculated the urea clearance from an APD treatment that provided a urea mass removal equivalent to CAPD. A total weekly Kt/Vurea was calculated for various levels of continuous urea clearance (defined as Kprt/Vurea) and plotted against Kprt/Vurea (weekly). The impact of dialytic time (t), drain volume of the daytime dwell (delta), and ultrafiltration volume (phi) were assessed, and all profiles were performed with C0 equal to the corresponding blood urea nitrogen of 60, 70, and 80 mg/dL.

RESULTS

The relationship between requisite weekly Kt/Vurea and Kprt/Vurea (weekly) was linear. Weekly Kt/Vurea declined with increasing Kprt/Vurea, t, delta, and phi. The effect of phi on the weekly Kt/Vurea was independent of Kprt/Vurea, and the magnitude of the effect of t and delta on the weekly Kt/Vurea decreased with increasing continuous clearance. Weekly Kt/Vurea values were independent of V and C0. The latter observation allowed extrapolation of CAPD clearance and urea generation relationships to APD: CAPD-equivalent weekly Kt/Vurea = [700 x (UD + Ur)]/(C0 x V), where UD and Ur are the daily urea mass (mg) in dialysate and urine, respectively.

CONCLUSIONS

The APD urea clearance, which provides urea mass removal equivalent to CAPD, varies as a function of a combination of patient and treatment variables. However, a CAPD-equivalent weekly Kt/Vurea can be calculated by collecting appropriate dialysis and urine samples and estimating patient V. The results can be evaluated in the context of evidence-based CAPD guidelines, increasing the precision of adjustment and monitoring of the APD prescription.

Tidal peritoneal dialysis: comparison of different tidal regimens and automated peritoneal dialysis

BACKGROUND

The National Kidney Foundation Dialysis Outcomes Quality Initiative (DOQI) clinical practice guidelines have suggested minimal weekly Kt/V urea and creatinine clearance goals for peritoneal dialysis patients maintained on continuous ambulatory peritoneal dialysis (CAPD) and automated peritoneal dialysis (APD). Achieving these goals may present problems, particularly in larger patients whose residual renal function declines. Thus, modifications of the dialysis regimen, such as tidal peritoneal dialysis (TPD), have been developed. However, the ability of TPD to improve the efficiency of the dialysis procedure remains uncertain.

METHODS

Stable, cycling peritoneal dialysis patients were placed into two groups to study the effectiveness of different TPD prescriptions on peritoneal clearances of urea and creatinine. The volume of dialysis solution used and the duration of therapy were fixed in the two groups. Comparisons were made to conventional APD using multiple hourly cycles in which spent dialysis solution was completely drained with each cycle. Group I patients received a total of 15 L of PD solution over 9.5 hours in the dialysis unit. These patients received 10, 25, and 50% TPD and APD on four separate days. Group II patients received 24 L of PD solution over 9.5 hours. These patients received 25 and 50% APD on separate days in the dialysis unit. Peritoneal dialysis clearances for urea (pKt/V) and creatinine (pCCr) levels were calculated for both groups. The results were then analyzed to determine whether there was any significant difference among the various prescriptions.

RESULTS

The data in the group I patients indicated a mean daily pKt/V of 0.22 +/- 0.03 with 10% TPD, 0.23 +/- 0.02 with 25% TPD, 0.25 +/- 0.02 with 50% TPD, and 0.26 +/- 0.02 with APD. Paired t-test analysis for pKt/V demonstrated that 10 and 25% TPD resulted in significantly lower values than 50% TPD and APD (P < 0.05). Mean daily pCCr L/24 h/1.73 m2 was 6.03 +/- 0.72 for 10% TPD, 6.34 +/- 0.83 for 25% TPD, 6.65 +/- 0.51 for 50% TPD, and 7.01 +/- 0.96 for APD; these differences were not significantly different. The data in the group II patients demonstrated a mean daily pKt/V of 0.28 +/- 0.03 with 25% TPD, 0.29 +/- 0.05 with 50% TPD, and 0.30 +/- 0.05 for APD. The mean daily pCCr was 6.69 +/- 0.47 for 25% TPD, 8.09 +/- 1.30 for 50% TPD, and 7.63 +/- 1.13 for APD. There were no statistical differences for pKt/V and pCCr within the 24 L group.

CONCLUSION

When the duration of therapy and volume of dialysate volume are kept constant, TPD does not result in an improvement in clearances compared with conventional APD, at least with dialysate volumes up to 24 L.

Dependence of peritoneal clearances on body size in continuous ambulatory peritoneal dialysis: effect of the normalizing size indicator

In peritoneal dialysis (PD), small solute clearances are normalized by body water (V) and body surface area (BSA). The purpose of this study was to identify if V or BSA produced stronger associations between body size and normalized clearances. We studied the relationship between four size indicators (V, BSA, height, and weight) and either peritoneal urea clearance normalized to V (Kt/V(ur)) and BSA (C(ur)) or creatinine clearance normalized to V (Kt/V(cr)) and BSA (C(cr)). A total of 613 clearance studies were performed in subjects on continuous ambulatory peritoneal dialysis (CAPD) with four daily exchanges and a 2 L fill volume. As size increased, the normalized peritoneal clearances decreased in a nonlinear fashion (regression: y = b0 + b1x(-1), where x is a size indicator and y is a normalized clearance). Significant (p < 0.001) negative correlations were found between each normalized clearance and each size indicator. However, in each case, the correlation was higher when V, rather than BSA, was used. For example, BSA correlated more closely with K/V(ur)(-0.660) than C(ur)(-0.556), and also with Kt/V(cr)(-0.579) than C(cr)(-0.446). Normalized clearances are smaller in large subjects on CAPD because one mathematic determinant of the clearance, the drain volume (Dv) normalized by V (Dv/V) or BSA (DV/BSA), decreases as size increases. The relationship between Dv/V or Dv/BSA and the size indicators was studied by the same nonlinear regression model. The correlations of the size indicators with Dv/V were also consistently higher than the corresponding correlations with Dv/BSA. In subjects who were on the same PD schedule, the dependence of clearances on size was consistently higher when V, rather than BSA, was the normalizing parameter. Because prescription of the dose of PD is based on body size, there is a practical advantage by using V as the sole normalizing parameter for both urea and creatinine clearance.

The relation between body size and normalized small solute clearances in continuous ambulatory peritoneal dialysis

The normalized peritoneal clearances of small solutes depend on the ratio of their concentration in dialysate and plasma (D/P) and the drain volume (Dv) corrected for some measure of body size such as body water (V) or body surface area (BSA). The clearance formulas (D/P) x (Dv/V) and (D/ P) x (Dv/BSA) can be used to examine why large individuals tend to be underdialyzed. Large people have low normalized drain volumes (Dv/V, Dv/BSA). It is not known whether size affects the D/P ratios. The purpose of this study was to examine the relationship between normalized peritoneal clearances (Kt/Vurea, CCr per 1.73 m2 BSA) and four size indicators (weight, height, V, BSA) in 301 patients on continuous ambulatory peritoneal dialysis (four daily exchanges with 2-L exchange volume) who underwent 613 clearance studies. Highly significant (P < 0.001) nonlinear relationships were found between Kt/Vurea and weight (r2 = 0.371), height (r2 = 0.289), BSA (r2 = 0.436), and V (r2 = 0.527); and between CCr and weight (r2 = 0.178), height (r2 = 0.115), BSA (r2 = 0.199), and V (r2 = 0.151). There were also significant negative correlations between the normalized drain volumes (Dv/V and Dv/BSA) and all four indicators of body size. Raw (not normalized) peritoneal clearances and drain volumes correlated positively with size. However, D/P(urea) or D/P(creatinine) did not vary with any size indicator except for a weak association between D/P(creatinine) and V (r = 0.089, P = 0.028). This association was not confirmed when V was used to stratify subjects into quartiles, and group differences for D/P(creatinine were tested by one-way ANOVA. This study shows that the exclusive cause of the low normalized peritoneal clearances in large subjects on continuous ambulatory peritoneal dialysis is a low normalized drain volume. No evidence was found to indicate that body size influences the D/P ratio of small solutes. The portion of the variance in normalized clearance explained by size varies by size indicator and solute (urea versus creatinine).

Peritoneal dialysis adequacy: a model to assess feasibility with various modalities

BACKGROUND

The current standard of adequacy for peritoneal dialysis (PD) is to provide a weekly normalized urea clearance (Kt/V) of 2.0 or more and a creatinine clearance (CCr) of 60 liter/1.73 m2 or more. As native renal function is lost, it is important to determine the effectiveness of the available therapeutic modalities in achieving these goals.

METHODS

A model to assess our ability to provide a weekly Kt/Vurea of 2.0 or more and a CCr of 60 liter/1.73 m2 or more to anuric patients undergoing continuous ambulatory PD (CAPD) and automated PD (PD Plus) was developed. The body surface area (BSA) distribution was obtained from 38,768 patients undergoing dialysis during January 1997. The distribution of peritoneal transport rates (PTRs) was obtained from 2531 peritoneal equilibration tests performed during 1996. The weekly Kpt/Vurea was calculated for the various PTR groups and the range of BSA with four PD prescriptions: CAPD 8 liters, CAPD 10 liters, PD Plus 12 liters, and PD Plus 15 liters, using a previously validated kinetic program (PackPD).

RESULTS

The predicted percentage of patients capable of achieving the adequacy goals for Kt/V and CCr, respectively, were 24.8 and 11. 2 for CAPD 8 liters, 54.2 and 33.0 for CAPD 10 liters, 77.8 and 54.9 for PD Plus 12 liters, and 93.2 and 72.9 for PD Plus 15 liters.

CONCLUSIONS

Most patients can attain the current adequacy standards of therapy with automated PD, but few (less than 25%) can do so with standard CAPD in the absence of residual renal function.

Cycler adequacy and prescription data in a national cohort sample: the 1997 core indicators report. Health Care Financing Administration Peritoneal Dialysis Core Indicators Study Group

BACKGROUND

The Health Care Financing Administration Peritoneal Dialysis Core Indicator Project obtains data yearly in four areas of patient care: dialysis adequacy, anemia, blood pressure, and nutrition.

METHODS

Adequacy and dialysis prescription data were obtained using a standardized data abstraction form from a random sample of adult U.S. peritoneal dialysis patients who were alive on December 31, 1996.

RESULTS

For the cohort receiving cycler dialysis, 22% were unable to meet the National Kidney Foundation Dialysis Outcome Quality Initiatives (NKF-DOQI) dialysis adequacy guidelines because they did not have at least one adequacy measure during the six-month period of observation. Thirty-six percent of patients met NKF-DOQI guidelines for weekly Kt/V urea, 33% met guidelines for weekly creatinine clearance (CCr), and 24% met guidelines for both urea and creatinine clearances. The mean weekly adequacy values were 2.24 +/- 0.56 for Kt/V urea and 67.5 +/- 24.4 liter/1.73 m2 for CCr, and the median values were 2.20 and 62.25 liter/1.73 m2, respectively. The mean prescribed 24-hour volume was 12,040 +/- 3255 ml, and the median prescribed volume was 11,783 ml. Only 60% of patients were prescribed at least one daytime dwell. By logistic regression analysis, risk factors for an inadequate dose of dialysis included being in the highest quartile of body surface area (odds ratio = 3.3 for CCr and 3.4 for Kt/V urea) and a duration of dialysis greater than two years (odds ratio = 4.2 for CCr and 2.1 for Kt/V urea).

CONCLUSION

There is much room for improvement in providing an adequate dose of dialysis to cycler patients. Practitioners should be more aggressive in increasing dwell volumes, adding daytime dwells, and adjusting nighttime dwell times in order to compensate for the loss of residual renal function over time. These changes can only be accomplished if practitioners measure periodically the dose of dialysis as outlined in the NKF-DOQI guidelines.

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

We studied whether anuric subjects on continuous ambulatory peritoneal dialysis (CAPD) who achieve the target Kt/V urea of 2.0 weekly will also achieve the target normalized creatinine clearance (NCCr) of 60 liter/1.73 m2 weekly, and the reasons of discrepancy between the two clearances in anuric subjects, by analyzing 476 clearance studies performed in 309 CAPD patients within 12 months of the performance of a peritoneal equilibration test (PET). On the basis of the PET, peritoneal solute transport was classified as low (37 clearance studies), low-average (199 studies), high-average (186 studies) and high (54 studies). We found that weekly values of Kt/V urea in the low transport group (LTG) was 1.74 +/- 0.51, in the low-average transport group (LATG) was 1.66 +/- 0.41, in the high-average transport group (HATG) 1.68 +/- 0.41, and in the high transport group (HTG) 1.73 +/- 0.46 (NS, variance analysis). Weekly values for NCCr, liter/1.73 m2 were: LTG, 37.8 +/- 9.0; LATG, 44.0 +/- 9.2; HATG, 49.2 +/- 10.0; HTG 56.8 +/- 13.3 (P < 0.0001). The ratios of raw (not-normalized) peritoneal creatinine clearance to peritoneal urea clearance were: LTG, 0.65 +/- 0.14; LATG, 0.76 +/- 0.09; HATG, 0.84 +/- 0.09; HTG, 0.91 +/- 0.12 (P < 0.0001). Linear regression with Kt/V urea as x and NCcr as y revealed the following results: LTG, y = 19.486 + 10.500x, r = 0.591 [if x = 2.0, y = 15.004 + confidence interval (95% CI) of y 25.3 to 55.7]; LATG, y = 15.0004 + 17.482x, r = 0.774 (if x = 2.0, y = 50.0, 95% CI of y 38.4 to 61.6); HATG, y = 15.285 + 20.162x, r = 0.829 (if x = 2.0, y = 55.6, 95% CI of y 44.4 to 66.8); HTG, y = 14.945 + 24.134x, r = 0.839 (if x = 2.0, y = 63.2, 95% CI of y 48.4 to 78.1). Peritoneal solute transport type has a major effect on peritoneal creatinine clearance, but an insignificant effect on peritoneal urea clearance. Consequently, the majority of anuric patients who achieve a weekly Kt/V urea of 2.0 will have a weekly NC cr lower than 60 liter/1.73 m2 and will require a Kt/V urea much higher than 2.0 to achieve the target NCcr of 60 liter/1.73 m2 weekly. The current targets of urea and creatinine clearance are not compatible in anuric patients on CAPD.