Low sodium to potassium ratio in spot urine sample is associated with progression to acute kidney injury and mortality in hospitalized patients with cirrhosis.

Background: sodium to potassium ratio in spot urine sample (Na/K) is a surrogate marker of sodium excretion that is recommended for the management of patients with ascites due to cirrhosis.

Aims: to investigate Na/K ratio and fractional excretion of sodium (FENa) in patients admitted with decompensated cirrhosis, evaluating its relationship with acute kidney injury (AKI) and prognosis.

Methods: prospective cohort study included 225 adult subjects. Urine samples were obtained within 48 h of hospitalization.

Results: AKI at admission was observed in 32.9% of patients and was associated with lower Na/K ratio, but not FENa. Among 151 subjects initially without kidney dysfunction, AKI at some point during hospitalization occurred in 26.2% and was independently associated with low Na/K ratio at admission. AKI was observed in 44% of the patients with Na/K ratio < 1 and only in 8% when values ≥ 2. Na/K ratio at admission was independently associated with 30-day mortality, with Kaplan-Meier survival probability of 78.8% for Na/K ratio < 1 and 93.6% for values ≥ 1.

Conclusions: low Na/K ratio in spot urine sample is associated with progression to AKI and lower short-term survival in patients hospitalized for decompensated cirrhosis.