Several studies in haemodialysis patients have shown that UCR level is significantly associated with an increased risk for all-cause mortality 21, 22, infection-related death and incidence of coronary heart disease 23. Over the past decade, UCR has been strongly associated with poor clinical outcomes in various population settings, such as acute kidney injury (AKI) 8, 9, acute decompensated heart failure 3, 10, 11, 12, 13, 14, chronic heart failure 15, 16, 17, acute myocardial infarction 18, 19 and ischaemic stroke 20. Increases in serum urea out of proportion to serum creatinine result in an elevated UCR and reflect a critical condition. Serum urea levels can be further increased by excess protein intake, hypovolaemia, heart failure, gastrointestinal bleeding and catabolism 7. In renal failure, serum urea and creatinine levels usually rise proportionally with a progressive decline in renal function 4, 5, 6. Because this process is regulated by both neurohormonal activity and renal function, the urea-to-creatinine ratio (UCR) has been proposed to be of value in clinical practice. Creatinine is not reabsorbed and is excreted from the body, however, approximately 40–50% of urea is reabsorbed in the tubules, where it is linked to reabsorption of sodium and water 3. Due to their small molecular sizes, both creatinine and urea are filtered by the glomerulus 2. Urea has traditionally been thought to be a relatively inert molecule, however, recent experimental data has suggested that it induces biochemical alterations with a potential impact on clinical outcomes 1.

The biological role of urea in chronic kidney disease (CKD) remains contentious. This warrants further investigation to understand the pathophysiological basis for this relationship and to identify effective interventions. Elevated urea-to-creatinine ratio is associated with poor clinical outcomes in chronic kidney disease inpatients. Despite this, there was no statistically significant association between higher urea-to-creatinine ratio and intensive care unit admission. Higher urea-to-creatinine ratio level was associated with greater rates of inpatient mortality, hospital readmission within 30-days and longer hospital length-of-stay. Age ≥ 65 years, female gender, gastrointestinal tract bleeding, heart failure, acute kidney injury and lower serum albumin were associated with elevated urea-to-creatinine ratio. This retrospective cohort study ( n = 11,156) included patients with at least two eGFR values 100 was present in 27.67% of hospital admissions. To better understand the role of the urea-to-creatinine ratio in chronic kidney disease patients, we assessed the epidemiology of the urea-to-creatinine ratio among hospitalised chronic kidney disease patients, and the association between the urea-to-creatinine ratio and inpatient clinical outcomes.

Bun creatinine normal range