FOLLOW-UP OF RESIDUAL RENAL-FUNCTION IN C APD PATIENTS - THE INFLUENCE OF PERITONEAL CLEARANCES AND DRUGS

With the intention of studying the outcome of residual renal function (RRF) at medium-long term, we have selected 38 patients for whon CAPD was their first dialytic treatment, maintained at least 3 years and wi th a diuresis higher than 100 ml/day at the start. RRF measured by cre atinine renal clearance (CrKr) showed a fast decrease after two years on CAPD (4.0 +/- 2.6 to 1.6 +/- 1.8 ml/min, p < 0.01). At this time on ly 50 % of the patients showed CrKr over 1 ml/min. Patients who mainta ined stable RRF showed no changes in weekly Kt/V-UN (urea nitrogen), K d-UN (peritoneal clearance) and Kd-Cr. However, those patients who los t their RRF showed a decrease of 18 % in their weekly Kt/V-UN and of 3 0 % in their total creatinine clearance. CrKr showed significant direc t correlation with Kt/V-UN, with EN-creatinine (efficacy number) and i nverse correlation with KdCr. Diabetic patients had a higher RRF than non diabetics (5.8 +/- 3.0 vs 3.1 +/- 1.8 ml/min, p < 0,01) at startin g. After one and two years on CAPD, diabetic patients showed more seve re decline of RRF than non diabetics (-1.8 +/- 3.1 vs -0.8 +/- 1.5 ml/ min/year respectively for the first year and -4.9 +/- 3.2 vs -0.9 +/- 2.0 ml/min/year, for the second year, both p <0.01). Gender, daily pro tein intake measured by PCR, weight, blood pressure, incidence of peri tonitis, administration of nephrotoxic antibiotics, biochemical/ usual controls or peritoneal clearances did not show any influence on the s lope of loss RRF. However, the patients receiving calcium channel bloc kers showed more significant decrease of RRF than those not receiving these drugs (-3.1 +/- 3.1 vs -1.0 +/- 2.2 ml/min/year, p <0.05 respect ively). This difference was more impressive among diabetics. ACE inhib itors showed no difference in these parameters. In conclusion, we have not detected any influence of small molecule peritoneal clearance in the decay of residual renal function in CAPD patients. Methodological problems or limitations in the response to therapy, derived from the a dvanced renal insufficiency, could be the causes. Residual renal funct ion declines significantly after two years on CAPD especially among di abetics and those patients taking calcium channel blockers.