Introduction

Although residual urine output (UOP) is associated with better survival and quality of life in dialysis patients, frequent measurement by 24-hour urine collection is burdensome. We thus sought to examine the association of patients' self-reported residual UOP, as an alternative proxy of measured residual UOP, with mortality risk in a prospective hemodialysis cohort study.

Methods

Among 670 hemodialysis patients from the prospective multicenter Malnutrition, Diet, and Racial Disparities in Kidney Disease study, we examined associations of residual UOP, ascertained by patient self-report, with all-cause mortality. Patients underwent protocolized surveys assessing presence and frequency of UOP (absent, every 1-3 days, >1 time per day) every 6 months from 2011 to 2015. We examined associations of baseline and time-varying UOP with mortality using Cox regression.

Results

In analyses of baseline UOP, absence of UOP was associated with higher mortality in expanded case-mix adjusted Cox models (ref: presence of UOP): hazard ratio (HR), 1.78 (95% confidence interval [CI], 1.16-2.72). In analyses examining baseline frequency of UOP, point estimates suggested a graded association between lower frequency of UOP and higher mortality, although estimates for UOP every 1 to 3 days did not reach statistical significance (reference: UOP >1 time per day): HR, 1.29 (95% CI, 0.82-2.05) and HR, 1.97 (95% CI, 1.24-3.12) for UOP every 1 to 3 days and absence of UOP, respectively. Similar findings were observed in analyses of time-varying UOP.

Conclusion

In hemodialysis patients, there is a graded association between lower frequency of self-reported UOP and higher mortality. Further studies are needed to determine the clinical impact of more frequent assessment of residual UOP using self-reported methods.

Cachexia and protein-energy wasting are potent predictors of higher mortality risk in dialysis-dependent chronic kidney disease (CKD) patients. The novel cachexia marker, GDF15, is a protein associated with inflammation, cardiovascular disease, and decreased survival in patients with underlying malignancy. However, the impact of GDF15 on the survival of CKD patients is unknown. Among 203 prevalent hemodialysis patients enrolled in the prospective MADRAD study over the period of 10/2011-8/2014, we examined the association of GDF15 levels with all-cause mortality risk. Associations between GDF15 categorized into tertiles with mortality were estimated using unadjusted and case-mix adjusted Cox models. Compared with the lowest GDF15 tertile, the highest GDF15 tertile was associated with higher mortality risk in unadjusted and case-mix adjusted models: HR (95%CI) 3.19 (1.35-7.55) and 2.45 (1.00-6.00), respectively, p-for-trend 0.03 (Figure 1A). Higher circulating GDF15 levels in hemodialysis patients are associated with higher all-cause mortality. Future studies are needed to determine whether modulation of GDF15 levels and subsequent correction of cachexia improves survival in this population.