Obesity predicts long survival in patients on hemodialysis

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1 Peritoneal Dialysis International, Vol. 22, pp Printed in Canada. All rights reserved /02 $ Copyright 2002 International Society for Peritoneal Dialysis NUTRITION INDICES IN OBESE CONTINUOUS PERITONEAL DIALYSIS PATIENTS WITH INADEQUATE AND ADEQUATE UREA CLEARANCE Antonios H. Tzamaloukas, Karen S. Servilla, Glen H. Murata, 1 and Richard M. Hoffman 1 Renal Section; General Internal Medicine Section, 1 New Mexico Veterans Affairs Health Care System and University of New Mexico School of Medicine, Albuquerque, New Mexico, USA 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 m 2 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 Correspondence to: A.H. Tzamaloukas, Renal Section (111C), New Mexico VA Health Care System, 1501 San Pedro SE, Albuquerque, New Mexico USA. Tzamalouka@aol.com Received 12 October 2001; accepted 20 March 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. Perit Dial Int 2002; 22: KEY WORDS: Obesity; nutrition; dialysis adequacy; anuria; residual renal function. Obesity predicts long survival in patients on hemodialysis (1,2). This beneficial effect of obesity is thought to be due to good nutrition. The impact of obesity on outcomes of continuous peritoneal dialysis (CPD) is less well established. One adverse outcome of obesity is a high rate of peritoneal catheter loss from catheter-related infections (3). The effect of obesity on survival of CPD patients needs to be studied in large cohort studies. Two small studies reported no effect of body size on survival of CPD patients (4,5); a third small study found that obese CPD patients survive longer than CPD patients with normal weight (6). In CPD patients, large body size, which creates difficulties in achieving adequate normalized small solute clearances (7 9), is usually due to obesity (10). Continuous ambulatory peritoneal dialysis (CAPD) is generally not capable of providing adequate clearances to obese patients (11). Obese individuals on CPD can obtain adequate clearances with the large daily fill volumes usually provided by automated peritoneal dialysis (10,12,13). Preliminary information suggests that Kt/V urea modulates the effect of obesity on survival of CPD patients (D. Raj et al., unpublished data). One of the potential effects of underdialysis is malnutrition (14). The present report tested the hypothesis that nutrition indices differ between obese CPD patients with inadequate and adequate Kt/V urea at the first clearance study after initiation of CPD.

2 PDI JULY 2002 VOL. 22, NO. 4 NUTRITION IN OBESE CPD PATIENTS METHODS We have collected clearance data from a large number of North American patients followed by dialysis units located in Albuquerque, New Mexico, and Pittsburgh, Pennsylvania, USA, and Toronto, Ontario, Canada. These patients started CPD between 1991 and We analyzed the small solute clearances and nutrition indices of 270 CPD patients that were obese at the first clearance study. Obesity was defined by the ratio of actual body weight (W) to desired weight (DW). Desired weight is the midpoint of the range of body weights associated with the greatest longevity for normal individuals within the same age range and of the same height, gender, and skeletal frame as the individual in question (15). Desired weights were obtained from the tables of the Metropolitan Life Insurance Company (16). We assumed that all patients had a medium skeletal frame. Patients with W/DW 1.2 were considered obese (17). The height ranges reported in the Metropolitan tables are cm for women and cm for men. For patients with heights outside the reported ranges, desired weight was obtained from linear regressions of height (H) on desired weight obtained from the Metropolitan tables. We obtained the following regression equations for a medium skeletal frame: DW Women = H, r = 0.999; DW Men = H, r = 0.996; where DW is in kilograms and H is in meters. Clearance studies were performed by collecting concomitant 24-hour drained dialysate and urine, followed by a blood sample. Standard methods were used to calculate Kt/V urea and creatinine clearance (CCr) (18,19). Urea clearance was normalized to body water (V) estimated from the Watson formulas (20). The methods used for measuring creatinine concentration in body fluids did not involve interference from glucose. Renal CCr was corrected for tubular secretion of creatinine by averaging renal urea and CCr (21). Creatinine clearance was normalized to 1.73 m 2 body surface area (BSA), which was estimated using the Dubois formula (22). Protein nitrogen appearance (PNA) was calculated by the Randerson method (23) and was normalized to both (actual body water)/0.58 (npna W ) and (body water at desired weight)/0.58 ( ). Lean body mass (LBM) was calculated from creatinine kinetics (24) and was normalized to both actual weight (LBM/W) and desired weight (LBM/DW). The statistical analysis included univariate comparisons. These comparisons included anthropometric data, demographic data, small solute clearances, and nutrition indices. Adequate level of Kt/V urea was set at 2.0 weekly (25). In the first set of comparisons, obese patients with actual (measured) Kt/V urea < 2.0 weekly were compared to patients with actual weekly Kt/V urea 2.0. In another set of comparisons, obese CPD patients with anuria were compared to patients with residual renal function, separately in the inadequately and adequately dialyzed groups. This last set of comparisons was performed because a report from the CANUSA study found that residual renal function plays an important role in the survival of CAPD patients (26). Continuous variables are expressed as mean ± standard deviation and were compared using the twotailed, nonpaired Student s t-test. Categorical variables were compared by chi-square. Differences at p < 0.05 were considered significant. Differences at 0.05 < p < 0.10 were considered marginal. RESULTS INADEQUATE VERSUS ADEQUATE UREA CLEARANCE Table 1 shows comparison of demographic and anthropometric variables between obese CPD patients with inadequate Kt/V urea (group I) and obese CPD patients with adequate Kt/V urea (group II). At the first clearance study, the majority of the obese CPD patients (58.1%) had inadequate Kt/V urea. Age, percent of patients with diabetes mellitus, and degree of obesity [W/DW, body mass index (BMI)] were almost identical between the two groups. The underdialyzed group contained a lower percentage of women and had larger height, desired weight, V, and BSA than the adequately dialyzed group. Duration of CPD until the first clearance study and actual weight were marginally larger in the underdialyzed group. Six women and 9 men, or 5.6% of the 270 obese CPD patients, had heights below the lowest height reported in the Metropolitan tables. No patient had a height taller than the tallest height reported in the Metropolitan tables. Table 2 shows clearance determinants and clearance values. Urine volume was lower in the underdialyzed group, which contained a higher percent of patients with anuria. Daily drain volume (Vd) did not differ between the groups, but the ratio Vd to body water (Vd/V) was lower in the underdialyzed group. Dialysate-to-plasma ratio (D/P) urea was lower in the underdialyzed group; D/P creatinine did not differ between the two groups. Peritoneal and renal Kt/V urea and renal CCr were lower in the underdialyzed group; peritoneal CCr did not differ between the two groups. 507

3 TZAMALOUKAS et al. JULY 2002 VOL. 22, NO. 4 PDI TABLE 1 Demographic and Anthropometric Variables in Underdialyzed (Group I) and Adequately Dialyzed (Group II) Obese Continuous Peritoneal Dialysis (CPD) Patients Table 3 shows nutrition indices. The underdialyzed group had higher serum urea and creatinine levels, and marginally lower serum albumin levels than the adequately dialyzed group. Urea nitrogen excretion and all indices derived from it (PNA, npna W, ) were lower in the underdialyzed group. Finally, creatinine excretion and indices derived from it [creatinine excretion normalized to actual (LBM/W) and desired weight (LBM/DW)] were also lower in the underdialyzed group. 508 Group I Group II p Value N 157 (58.1%) 113 (41.9%) Female gender 62 (39.5%) 68 (60.2%) <0.001 Age (years) 55.5± ±13.5 N S Patients with diabetes 83 (52.9%) 60 (53.1%) N S CPD duration a (months) 7.2± ± Height (cm) 167.3± ± Weight (kg) 89.0± ± V Watson (L) 42.4± ± BSA (m 2 ) 1.98± ± Desired weight (kg) 64.6± ± W/DW 1.38± ±0.19 N S BMI (kg/m 2 ) 31.8± ±4.1 N S NS = not significant; V = body water; BSA = body surface area; W = actual weight; DW = desired weight; BMI = body mass index. a Until the first clearance study. TABLE 2 Clearance Determinants and Weekly Clearances in Underdialyzed (Group I) and Adequately Dialyzed (Group II) Obese Continuous Peritoneal Dialysis Patients Group I Group II p Value Vu (L/24 hours) 0.30± ±0.67 <0.001 Patients with anuria 55 (35.0%) 10 (8.8%) <0.001 Vd (L/24 hours) 10.2± ±3.0 N S Vd/V Watson (L/L/24 hr) 0.243± ± D/P urea 0.87± ±0.11 <0.001 D/P creatinine 0.72± ±0.14 N S Kt/V urea, peritoneal 1.46± ±0.44 <0.001 Kt/V urea, renal a 0.30± ±0.62 <0.001 Kt/V urea, total 1.66± ±0.47 <0.001 CCr peritoneal (L/1.73 m 2 ) 43.9± ±12.1 N S CCr renal a (L/1.73 m 2 ) 18.4± ±36.9 <0.001 CCr total (L/1.73 m 2 ) 55.6± ±29.8 <0.001 Vu = urine volume; Vd = dialysate drain volume; NS = not significant; V = body water; D/P = ratio of dialysate concentration (in Vd) to plasma concentration; CCr = creatinine clearance. a Only in patients with residual renal function. TABLE 3 Nutrition Indices in Underdialyzed (Group I) and Adequately Dialyzed (Group II) Obese Continuous Peritoneal Dialysis Patients Group I Group II p Value Serum urea (mmol/l) 20.7± ± Serum creatinine (μmol/l) 974± ±275 <0.001 Serum albumin (g/l) 35.8± ± UN Ex (mg/24 hours) 5778± ±2238 <0.001 PNA (g/24 hr) 58.9± ±16.7 <0.001 npna W (g/kg/24 hr) 0.81± ±0.21 <0.001 (g/kg/24 hr) 0.98± ±0.26 <0.001 Cr Ex (mg/24 hr) 1034± ±432 <0.001 (Cr Ex)/W (mg/kg/24 hr) 11.5± ±3.9 <0.001 (Cr Ex)/DW (mg/kg/24 hr) 15.8± ±5.5 <0.001 LBM (kg) 48.3± ±14.7 N S LBM/W 0.54± ± LBM/DW 0.74± ± UN = urea nitrogen; Ex = excretion; PNA = protein nitrogen appearance; npna = normalized PNA; W = actual weight; DW = desired weight; Cr = creatinine; LBM = lean body mass; NS = not significant. ANURIA VERSUS PRESENCE OF RESIDUAL RENAL FUNCTION Inadequately Dialyzed Patients: Of the 157 obese CPD patients with inadequate Kt/V urea, 55 (35.0%) had anuria. Compared to the inadequately dialyzed patients with residual renal function, those with anuria had longer duration of CPD until the first clearance study (9.8 ± 5.4 vs 5.8 ± 4.6 months, p = 0.014); larger daily drain volume (Vd; 10.8 ± 2.8 vs 9.8 ± 1.9 L/ 24 hr, p = 0.017) and ratio Vd/V Watson (0.265 ± vs ± L/L/24 hr, p < 0.001); marginally higher BMI (32.6 ± 4.5 kg/m 2 vs 31.4 ± 3.4 kg/m 2, p = 0.076) and percent of women (49.1% vs 34.3%, p = 0.071); and lower height (164.2 ± 12.5 vs ± 10.7 cm, p =0.020), weekly CCr (47.7 ± 10.3 vs 59.9 ± 15.7 L/1.73 m 2, p < 0.001), and weekly Kt/V urea (1.61 ± 0.24 vs 1.68 ± 0.20, p =0.079). No differences between the groups were found in W/DW, percent of patients with diabetes mellitus, age, weight, BSA, and V Watson. Table 4 shows nutrition indices in underdialyzed obese CPD patients with anuria and those with residual renal function. Serum urea, creatinine, and albumin, and urea nitrogen excretion and indices derived from it (PNA, npna W, ) did not differ between the groups. Creatinine excretion and indices derived from it (LBM, LBM/W, LBM/DW) were all lower in the anuric group. Adequately Dialyzed Patients: Among 113 obese CPD patients with adequate Kt/V urea, 10 (8.8%) had anuria. Compared to adequately dialyzed obese pa-

4 PDI JULY 2002 VOL. 22, NO. 4 NUTRITION IN OBESE CPD PATIENTS TABLE 4 Nutrition Indices in Underdialyzed Obese Continuous Peritoneal Dialysis Patients with Anuria (Anuric Group) and Those with Residual Renal Function (RRF Group) tients with residual renal function, the anuric patients had longer duration of CPD until the first clearance study (7.2 ± 4.5 vs 4.1 ± 2.7 months, p = 0.003); higher percent of patients with diabetes mellitus (80% vs 43.7%, p = 0.044), daily drain volume (Vd; 14.6 ± 4.3 vs 10.0 ± 2.5 L/24 hr, p < 0.001), and ratio Vd/W Watson (0.397 ± vs ± L/L/24 hr, p < 0.001); and lower weekly CCr (66.8 ± 9.7 vs 89.6 ± 30.4 L/1.73 m 2, p = 0.020). Percent of women, age, height, weight, BSA, V Watson, BMI, W/DW, and weekly Kt/V urea did not differ between the groups. Table 5 shows nutrition variables. The anuric group had higher serum creatinine. All other indices did not differ. DISCUSSION Anuric R R F group group p Value Serum urea (mmol/l) 20.6± ±6.6 N S Serum creatinine (μmol/l) 1014± ±308 N S Serum albumin (g/l) 34.9± ±5.8 N S UN Ex (mg/24 hours) 5416± ±2198 N S PNA (g/24 hr) 56.2± ±16.4 N S npna W (g/kg/24 hr) 0.80± ±0.20 N S (g/kg/24 hr) 0.97± ±0.26 N S Cr Ex (mg/24 hr) 886± ±343 <0.001 (Cr Ex)/W (mg/kg/24 hr) 10.1± ±3.7 <0.001 (Cr Ex)/DW (mg/kg/24 hr) 14.0± ±4.5 <0.001 LBM (kg) 44.4± ± LBM/W 0.50± ± LBM/DW 0.71± ± NS = not significant; UN = urea nitrogen; Ex = excretion; PNA = protein nitrogen appearance; npna = normalized PNA; W = actual weight; DW = desired weight; Cr = creatinine; LBM = lean body mass. The classification of degree of obesity of CPD patients is usually done by height/weight indices including BMI (6) and deviation of actual weight from ideal weight (10,27). In this study, we used the deviation of actual weight from desired weight to define obesity because of both the relevance of desired weight to survival of the general population (15) and the failure of BMI classifications to distinguish between genders. One problem with the classification of obesity by deviation of actual weight from desired weight is that the range of heights for which desired weights have been reported is relatively narrow (16). The desired weights for heights outside the range of heights reported in the Metropolitan tables are questionable. TABLE 5 Nutrition Indices in Adequately Dialyzed Obese Continuous Peritoneal Dialysis Patients with Anuria (Anuric Group) and Residual Renal Function (RRF Group) Anuric R R F group group p Value Serum urea (mmol/l) 20.7± ±5.0 N S Serum creatinine (μmol/l) 908± ± Serum albumin (g/l) 36.8± ±6.5 N S UN Ex (mg/24 hours) 7294± ±2155 N S PNA (g/24 hr) 70.2± ±16.1 N S npna W (g/kg/24 hr) 0.12± ±0.19 N S (g/kg/24 hr) 1.29± ±0.24 N S Cr Ex (mg/24 hr) 1049± ±422 N S (Cr Ex)/W (mg/kg/24 hr) 13.5± ±6.1 N S (Cr Ex)/DW (mg/kg/24 hr) 17.1± ±5.9 N S LBM (kg) 47.0± ±14.1 N S LBM/W 0.59± ±0.12 N S LBM/DW 0.77± ±0.17 N S NS = not significant; UN = urea nitrogen; Ex = excretion; PNA = protein nitrogen appearance; npna = normalized PNA; W = actual weight; DW = desired weight; Cr = creatinine; LBM = lean body mass. In the present study, only 5.6% of the patients had heights outside this range. Differences between various height/weight methods of classifying CPD patients as obese have been reported (28,29). For medium skeletal frame CPD patients, BMI values of 27.5 kg/m 2 for women and 27.8 kg/m 2 for men correspond to a W/DW of 1.2 (29), which was used as the cutoff value for obesity in the present study. Johnson et al. classified as obese CPD patients with BMI 27.5 kg/m 2 (6). Therefore, the classifications of CPD patients in Johnson s study and in the present study agree. Indeed, only 3 of the 270 patients (1.1%), all women, classified as obese in the present study had BMI values < 27.5 kg/m 2 ( kg/m 2 ). Obesity is frequent in American CPD patients. In a representative sample, Flanigan et al. reported a mean BMI of 27.0 kg/m 2 (30). Therefore, approximately 50% of American CPD patients are overweight or obese. In comparison to patients with normal weight, obese patients tend to have both greater difficulty in achieving adequate clearances and higher values of nutrition indices (30 33). This raises the issue of the relationship between small solute clearances and nutrition in CPD. The view that underdialysis is the major cause of malnutrition in CPD has been challenged (34). However, there is evidence that underdialysis worsens malnutrition in CPD patients with weight deficit (35). The effect of underdialysis on survival of obese CPD patients has not been studied. Underdialysis appears to exert a 509

5 TZAMALOUKAS et al. JULY 2002 VOL. 22, NO. 4 PDI negative influence on the survival of obese patients on hemodialysis (36). In the present study, calculations of small solute clearances and classification of patients as inadequately or adequately dialyzed were performed according to the Kidney Disease Outcomes Quality Initiative (K/DOQI) standards (25). However, some theoretical and practical difficulties with the determination of adequate small solute clearances in obese CPD patients should be noted. The K/DOQI guidelines have set higher Kt/V urea and CCr targets for underweight than normal-weight CPD patients (25). The rationale for this recommendation was that underweight patients should have clearances adequate not only for their current small size, but also for a larger body size, since weight gain is targeted for such patients. The same guidelines did not alter target clearances for obese CPD patients because a clear-cut indication for weight loss in such patients does not exist. Therefore, the target Kt/V urea and CCr levels for obese and normal-weight CPD patients are the same. Levels of small solute clearance associated with optimal survival and with morbidity in obese CPD patients will need further study. The practical difficulty with the calculation of Kt/V urea is that recent evidence strongly suggests that V estimated by the Watson formulas systematically overestimates body water in obese CPD patients without volume disturbances (37). Therefore, it is possible that the present study underestimated Kt/V urea in patients without volume expansion (38). However, the degree of obesity was the same in groups I and II (Table 1), and any systematic errors would be the same in both groups. The majority (58.1%) of the obese patients in the present study were receiving an inadequate, by K/DOQI standards, Kt/V urea at the first clearance study. The majority of the studies with inadequate clearances were obtained during the early years of this study, when the target clearances were lower than the current standards. Prescription of the dose of dialysis required to achieve a target clearance in CPD patients with large body size, including obese patients, has received special attention in recent years (39). Detailed prescription programs are available (40 42) and should be applied in calculating prescribed dose and schedule of CPD for every patient. Commercially available computer programs are the easiest way to obtain accurate prescriptions. Certain characteristics of the adequately and inadequately dialyzed groups are worth noticing. The percent of women in the underdialyzed group was disproportionately low (Table 1). This gender difference was due to both the smaller size of women and the relatively low volume of body water in women compared to men (43). The gender difference between 510 underdialyzed and adequately dialyzed obese CPD patients became marginal when we used a weekly CCr of 60 L/1.73 m 2 instead of a weekly Kt/V urea of 2.0 as the cutoff value for underdialysis. The reasons for underdialysis in the present study were both a larger percent of patients with anuria and a lower ratio of daily drain volume to body water (Vd/V) in the underdialyzed group (Table 2). Adequate Vd/V is critical in achieving target peritoneal Kt/V urea values in any given CPD schedule (9,44). Nutrition indices were uniformly worse in underdialyzed than in adequately dialyzed obese CPD patients (Table 3). In addition to their normalization by actual weight, indices derived from urea nitrogen and creatinine excretion were also normalized to desired weight because normalization of these indices by actual weight tends to produce, in large CPD patients, unrealistically low values that do not agree with other nutrition indices (45). The recommended dietary protein intake for PD patients is 1.2 g/kg/24 hr (46). The average was adequate in the adequately dialyzed group, but not in the inadequately dialyzed group (Table 3). The differences between the underdialyzed and the adequately dialyzed groups in nutrition indices derived from urea nitrogen and creatinine excretion could be due, at least in part, to mathematical coupling between small solute clearance and excretion, which occurs in cross-sectional CPD studies (47). However, robust published evidence suggests that the differences in small solute excretion between groups I and II (Table 3) may still be clinically important. In one prospective study, cross-sectional differences in small solute excretion at the onset of CPD were independent predictors of patient survival (48). In a retrospective study, the ratio of measured-to-predicted creatinine production was found to be an independent predictor of several outcomes in CPD, including survival (49). Creatinine excretion represents approximately 80% of the creatinine production in CPD (50). Therefore, the differences in creatinine production observed in this last study (49) represent, by and large, differences in creatinine excretion. The differences in creatinine excretion, and indices derived from it, between underdialyzed and adequately dialyzed obese patients in the present study are even more significant because the adequately dialyzed group, which had higher creatinine excretion, contained a disproportionately high number of women. Female gender predicts low, not high, creatinine excretion in CPD (51). In the final set of comparisons, we compared nutrition indices between obese patients with and those without anuria. Szeto et al. found independent effects of residual renal function and small solute clearances on nutrition in CPD patients (52). In a reanalysis of the CANUSA study, Bargman et al. reported recently

6 PDI JULY 2002 VOL. 22, NO. 4 NUTRITION IN OBESE CPD PATIENTS that residual urine volume was the only determinant of small solute clearances predicting survival (26). In CPD patients, residual urine volume is the major determinant of renal Kt/V urea (53). We found that creatinine excretion and all nutrition indices derived from it were substantially lower in anuric than in nonanuric obese CPD patients with underdialysis (Table 4). The anuric subgroup contained marginally more women than the nonanuric group. The differences in creatinine excretion persisted when we compared anuric to nonanuric men and anuric to nonanuric women. In adequately dialyzed patients, there were no differences in creatinine excretion (Table 5), even though the anuric subgroup had lower CCr than the subgroup with residual renal function. In summary, inadequate Kt/V urea was associated with globally depressed nutrition indices in obese patients on CPD. Among underdialyzed obese CPD patients, those with anuria had lower creatinine excretion than those with residual renal function. No differences in creatinine excretion or any other nutrition indices were observed between adequately dialyzed obese CPD patients with anuria and those with residual renal function. ACKNOWLEDGMENTS This work was supported by the New Mexico VA Health Care System. An abstract containing parts of this manuscript was submitted to the 22nd Annual Conference on Dialysis, held in Tampa, Florida, USA, March 4 to 6, REFERENCES 1. Fleischmann E, Teal N, Dudley J, May W, Bower JD, Salahudeen AK. Influence of excess weight on mortality and hospitalization in 1346 hemodialysis patients. Kidney Int 1999; 55: Kopple JD, Zhu X, Lew DL, Lowrie EG. Body weightfor-height relationships predict mortality in maintenance hemodialysis patients. Kidney Int 1999; 56: Piraino B, Bernardini J, Centa PK, Johnston JR, Sorkin MI. 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