The Tubulointerstitium in Health and Disease: More Than What Meets the Eye.

The tubulointerstitium is a critical component of the nephron. It is a highly vascularized compartment that plays an important part in kidney health and function. The tubulointerstitium orchestrates the clinical effects of volume control, electrolyte and acid-base balance, medication and toxin secretion, hormone production, immunological and inflammatory processes, and tubular repair processes. These important interconnected processes within the tubulointerstitial compartment that are independent of glomerular filtration require an intact tubulointerstitium to achieve optimal kidney function. When cellular injury occurs due to toxic, oxidative, inflammatory, and other insults and the repair processes to address this damage are incomplete, absent or untoward, acute and chronic tubulointerstitial disease develops. Direct tubular injury and deleterious inflammatory processes play important roles in tubulointerstitial nephritis. Over time, tubular atrophy, interstitial fibrosis and eventually glomerulosclerosis occurs. It is therefore not surprising that various forms of injury in this compartment can impair the previously described homeostatic processes.