1.5 mg/dl. Based on the number of these factors, a patient's risk for developing worsening renal function ranged between 16% (< or =1 factor) and 53% (> or =5 factors). After adjusting for confounding effects, worsening renal function was associated with a significantly longer length of stay by 2.3 days, higher in-hospital cost by $1,758, and an increased risk of in-hospital mortality (odds ratio 2.72; 95% confidence interval 1.62 to 4.58). In conclusion, worsening renal function, an event that frequently occurs in elderly patients hospitalized with heart failure, confers a substantial burden to patients and the healthcare system and can be predicted by 6 admission characteristics.