Relationship of urine output to dialysis initiation and mortality in acute renal failure

Background: A non-oliguric state is considered a good prognostic indicator in acute renal failure (ARF), and may lead to withholding renal replacement therapy in anticipation of recovery. The present study explores the relationship between urine volume and the start of dialysis and hospital mortality in patients with ARF.

Methods: In a non-concurrent cohort of patients with ARF treated exclusively with intermittent hemodialysis (IHD), demographic, clinical and laboratory characteristics were collected at the time of the first nephrology consultation and at the start of dialysis. Multiple linear and logistic regression analyses were used to identify factors associated with the time to initiation of dialysis and hospital mortality, respectively.

Results: Urine volume correlated with the time from admission to start of dialysis (r = 0.60; p < 0.001). Higher urine volume, lower serum creatinine and lower APACHE II score were independently associated with increased time from admission to start of dialysis. Hospital mortality was independently associated with a higher urine volume (odds ratio, OR 3.8, 95% confidence interval, CI, 1.1-12.8, p = 0.03), a higher MOF score (OR 4.9, 95% CI 1.1-21.6, p = 0.03) and a higher number of dialysis treatments performed in the 1st week (OR 3.7, 95% CI 1.2-11.3, p = 0.03).

Conclusions: Among patients with ARF requiring IHD, increased urine output is associated with higher mortality. This observation may reflect physician bias toward later initiation of dialysis in non-oliguric ARF. Further research is needed to help identify patients with non-oliguric ARF who require early dialytic support.