Urea and creatinine concentration, the urea: creatinine ratio

This is the second of two articles that together aim to explore current understanding of the clinical value of measuring serum/plasma urea concentration. The main focus of the first article [1] was physiological topics, such as urea production and renal processing of urea. The causes of increased and reduced plasma/serum urea concentration were also discussed. The main focus of this second article is the clinical value of simultaneous measurement of urea and creatinine and calculation of the urea: creatinine ratio. The causes of increased and decreased ratio will be outlined and clinical application of the ratio will be discussed. The article begins with a short discussion of the comparative merits of urea and creatinine measurement for assessment of renal function; this discussion is helpful for an understanding of the potential clinical value of calculating the ratio.