Residual kidney function in nocturnal vs conventional haemodialysis patients: a prospective observational study

Residual kidney function (RKF) provides substantial volume and solute clearance even after dialysis initiation. Preservation of RKF is associated with improved outcomes including mortality in patients on both peritoneal and haemodialysis (HD). Factors predicting RKF loss are unclear, including HD modality. Nocturnal haemodialysis (NHD) may result in less aggressive fluid and solute shifts, however, retrospective data suggests frequent NHD may accelerate RKF decline. The aim of the study was to determine if decline in RKF differs between patients undergoing conventional haemodialysis (CHD) versus NHD.

A prospective observational study of incident HD patients was undertaken comparing patients undertaking CHD (4-5 h, 3 days/week) and NHD (8 h, 3-5 nights/week). Change in RKF was measured by urea and creatinine clearance (48-h interdialytic urine collection) and glomerular filtration rate (GFR) (Cr51-EDTA nuclear scan) at initiation of dialysis (baseline) and 12 months.

A total of 18 incident HD patients were recruited (8 CHD, 10 NHD). Three patients withdrew after baseline (n = 15). Baseline RKF was similar between groups with mean nuclear GFR of 13.3 ± 4.1 mL/min in the CHD cohort vs 13.5 ± 4.6 mL/min in the NHD group (p = 0.89). Baseline urine volume was 2399 ± 950 mLs and 2794 ± 1662 mLs in the CHD and NHD, respectively (p = 0.57). Nuclear GFR declined from time 0 to 12 months to 9.3 ± 2.5 mL/min and 10.4 ± 4.3 mL/min in the CHD and NHD, respectively (p = 0.52). There was a significant decline in 48-h urine volume over 12 months with a mean volume of 1943 ± 1087.0 mLs in the CHD compared to 601.7 ± 315.3 mLs in the NHD (p = 0.01). No significant difference was found in other measures of RKF between groups over 12 months.

This small prospective cohort study found that the loss of residual urine volume was greater in the NHD vs the CHD cohort but there was no difference in other measures of RKF.