Question

Explain how the plasma urea level increases with age irrespective of the absence of a renal disease

Answer 1

The plasma level of urea increases with age because glomerular filtration rate (GFR) and renal blood flow (RBF) decreases with age as the glomerular capillary plasma flow rate, and the glomerular capillary ultrafiltration coefficient decrease with age. In addition, a primary reduction in afferent arteriolar resistance is associated with an increase in glomerular capillary hydraulic pressure. These hemodynamic changes occur in concert with structural changes, including loss of renal mass; hyalinization of afferent arterioles and in some cases, development of aglomerular arterioles; an increase in the percentage of sclerotic glomeruli; and tubulointerstitial fibrosis.