Chronic Tubulointerstitial Disease

Primary interstitial kidney disease comprises a diverse group of disorders that elicit interstitial inflammation associated with tubular damage. Traditionally, interstitial nephritis has been classified morphologically and clinically into acute and chronic forms. Acute interstitial nephritis (AIN) generally induces rapid deterioration in kidney function with a marked interstitial inflammatory response characterized by mononuclear cell infiltration with or without eosinophils, interstitial edema, and varying degrees of tubular cell injury. This process typically spares both glomerular and vascular structures, and is discussed more fully in Chapter 33. By contrast, chronic interstitial nephritis (CIN) follows a more indolent course and is characterized by interstitial fibrosis, tubular atrophy, and most often an interstitial mononuclear cell infiltrate. Over time, glomerular and vascular structures are involved, with progressive parenchymal fibrosis and sclerosis. Overlap can occur between these two clinical conditions; AIN sometimes presents as a more insidious disease with progression to chronic kidney disease (CKD). Similarly, some forms of CIN are associated with acute tubular cell injury.