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Abstract Background and Aims Residual kidney function (RKF) is a key component for PD adequacy and associated with improved volume status, nutrition and quality of life as well as with increased survival. The aim of the present study was to compare decline of kidney function before and after start of PD. Method We studied patients starting PD (during 2000-2019) in an ongoing prospective study of patients starting dialysis. Study inclusion in almost all PD patients coincided with PD catheter insertion. Patients were included in the present analysis if they had at least one urinary collection before, and one after PD initiation (a), PD initiation less than six months after study inclusion (b) and 6 months PD treatment (c). P-creatinine to calculate eGFR was retrospectively collected for 12 months before start of PD. During a large part of the study period, it was a clinical routine to collect 24-hour urine collections regularly in CKD5 patients, and these data were retrieved when available. After start of PD, regular 24-hour urine collections were part of the clinical routine to follow up and were retrieved for up to 12 months after PD start. eGFR was measured using the CKD-epi 2021 equation and GFR was calculated as the average of urinary creatinine and urea clearance corrected for BSA. The decline of eGFR before start of PD, the decline of GFR from 24-hour urine collections and the decline of GFR after start of PD were compared to each other. Results We studied 138 patients starting PD. The mean age was 55 ± SD13 years, and there were 80 males and 58 females. The mean blood pressure was 153 ± SD21/89 ± SD11 mmHg and BMI was 25 ± SD4 kg/m2. The etiologies of end stage kidney disease were nephrosclerosis 17%, diabetic nephropathy 22%, glomerulonephritis 25%, polycystic kidney disease 14% and other 22%. The GFR at PD start was 8.5 ± SD 2.3 mL/min/1,73 m² and eGFR was 5.8 ± SD 1.9 mL/min/1,73 m². The results show a significantly slower kidney function decline rate after start of PD, with an average of −0.59 mL/min/1,73 m²/month before PD initiation compared to −0.34 mL/min/1,73 m²/month after. Conclusion Decline of GFR was slower after start of PD suggesting that earlier initiation of dialysis may be beneficial for the preservation of RKF. Notably, there was a marked attenuation after 3 months of dialysis. Furthermore, the decline rate of GFR before PD start was similar using eGFR or GFR from 24-h urine collection, though for eGFR at somewhat lower levels. However, there were pronounced differences between those two methods in individual patients demonstrating that eGFR is unreliable with very low GFR. Further study will be performed to analyze what factors that are associated with better preservation of RKF.
Björksten et al. (Wed,) studied this question.