Section 1 -

Introduction Donna J. Lager, M.D. Matthew Lewin, M.D.

Renal diseases can be broadly classified as affecting three compartments: the glomeruli, the tubules and interstitium and the vasculature. Tubulointerstitial and vascular diseases are the subject of this course. The tubulointerstitial compartment comprises approximately 80% of the renal volume. The interstitial space is made up of both cellular and matrix components. The cells include fibroblast-like cells, and lipid-rich interstitial cells in the inner medulla; and monocytes and dendritic antigen-presenting cells found primarily in the cortex. The interstitial compartment provides structural support for individual nephrons, is involved in solute transport and is the site of production of hormones and cytokines. Diseases affecting the tubulointerstitial compartment may result from primary injury to this compartment, or may be secondary to injury to the other compartments. Changes in the tubulointerstitial compartment are a better predictor of the severity of renal dysfunction and long-term outcome than changes in other compartments. The renal artery which enters the kidney at the renal hilum, carries about one-fifth of the cardiac output. The renal artery bifurcates several times after entering the kidney and branches into arcuate arteries which run in an arch-like fashion along the corticomedullary junction. The arcuate arteries give rise to the interlobular arteries which run to the surface of the kidney and from which arise the afferent arterioles supplying the glomeruli. As the blood leaves the glomerulus, the capillaries coalesce into the efferent arteriole, which almost immediately bifurcates again to form the peritubular capillary network. The peritubular capillaries coalesce to form venules and eventually the renal vein.