Acute and Chronic Tubulointerstitial Nephritis

Cellular and fluid exudation in the interstitial tissue was noted by Councilman in 1898, while he studied kidneys of patients who died of scarlet fever and diphtheria (1). Councilman also determined that these kidneys did not contain bacteria (they were sterile). He called the condition acute interstitial nephritis (AIN). The term interstitial nephritis connotes predominant involvement of the renal interstitium and tubules by inflammatory cells, often with edema or fibrosis and tubular atrophy. Because interstitial nephritis is commonly accompanied by variable tubular damage, the term tubulointerstitial nephritis (TIN), or tubulointerstitial nephropathy, is preferable and is often used interchangeably with interstitial nephritis. TIN has two common clinical presentations: sudden onset and rapid decline in renal function—acute TIN—and protracted onset with slow decline in renal function—chronic TIN. Because chronic TIN may present with prominent fibrosis and few inflammatory cells, the term chronic tubulointerstitial fibrosis, or chronic tubulointerstitial nephropathy, is used by some. Tubulitis refers to infiltration of the tubular epithelium by leukocytes, usually mononuclear cells. Acute TIN, with time, can evolve into chronic TIN; therefore, overlaps between these two entities often exist. Terminology 1111