Urine volume in acute kidney injury: How much is enough

Abstract

Eight hundred and seventy-nine patients with acute kidney injury were retrospectively studied over year and eleven months for evaluation of urine volume as a risk factor for death. They were divided into five groups, according to the 24 h urine volume (UV): anuric (UV ≤ 50 mL24 h, group 1), oliguric (UV > 50 mL24 h and < 400 mL24 h, group 2), and non-oliguric (UV ≥ 400 mL24 h). Nonoliguric group was subdivided in three subgroups: UV > 400 mL24 h and ≤ 1000 mL24 h (group 3, reference group), UV > 1000 mL24 h and ≤ 2000 mL24 h (group 4), and UV > 2000 mL24 h (group 5). Linear tendency test (Mantel extension) pointed out a significant increase in mortality with UV decrease (p < 0.001), confirmed by multivariate analysis. Anuric and oliguric patients had increased risk of respectively 95 and 76 times for death compared to controls (p < 0.05). Patients from groups 4 and 5 presented a reduced risk for death of 50 and 70, respectively, p 0.004 and p 0.001. In conclusion, urine volume was a strong independent factor for mortality in this cohort of AKI patients. © 2009 Informa UK, Ltd.