DIETARY-PROTEIN, UREA NITROGEN APPEARANCE AND TOTAL NITROGEN APPEARANCE IN CHRONIC-RENAL-FAILURE AND CAPD PATIENTS

This study was carried out to examine the mathematical relationships b etween the urea nitrogen appearance (NA), total nitrogen appearance (T NA) and dietary nitrogen intake (DNT) in patients with chronic renal f ailure. Studies were conducted in 20 nondialyzed patients with advance chronic renal failure (CRF) who were fed 27 constant protein diets fo r 24.8 +/- 9.5 days (SD) and eight patients undergoing continuous ambu latory peritoneal dialysis (CAPD), who ingested 13 constant protein di ets for 20.3 +/- 4.9 days. All patients lived in a hospital research w ard throughout the study and underwent full nitrogen balance measureme nts. Data were analyzed after patients attained equilibrium or near eq uilibrium with each dietary protein intake. In the CRF patients, using the mean values obtained during the equilibrium phase there was a dir ect and precise correlation between the TNA and UNA, where TNA g/day = 1.19 UNA g/day + 1.27 g/day, r = 0.948. The correlation between DNI a nd UNA was also highly significant, but less precise with somewhat gre ater 95% confidence intervals: DNI g/day = 1.20 UNA g/day + 1.74 g/day , r = 0.865. The relationship between DNI and TNA was not much more pr ecise. DNI g/day = 0.97 TNA g/day + 0.65 g/day, r = 0.880. With the CA PD patients, the relationships were as follows: TNA g/day = 0.94 UNA g /day + 5.54 g/day, r = 0.956; DNI g/day = 0.97 UNA g/day + 6.80 g/day, r = 0.705; DNI g/day = 1.07 TNA g/day + 0.63 g/day, r = 0.760. For th e CAPD patients, the TNA is highly and precisely correlated with the U NA. The DNI is also significantly correlated with UNA and TNA, but the relationship is less precise. In both of these two groups of patients , the difference between the regression equations for TNA versus UNA a nd DNI versus UNA was, to a substantial degree accounted for by the in tercept.