Tubulointerstitial Nephritis - A Histopathological Study of Renal Biopsies.

Tubulointerstitial nephritis (TIN) is a frequent cause of acute kidney injury. TIN has a reported incidence ranging from 1% to 10% of all renal biopsies. Among patients with chronic renal failure, the incidence ranges from about 22% to 33.5%. We studied the histological features of renal biopsies with TIN, evaluated its etiology and correlated TIN with clinical features and investigations. Our study extended over a period of seven years, with 50 cases. The slides were stained with hematoxylin and eosin and special stains like periodic acid-Schiff, Jones methenamine silver and Masson's trichrome. All adequate renal biopsies showing features of acute and chronic TIN were included in our study. Renal biopsies showing features of only primary glomerular pathology and inadequate biopsies were excluded from the study. TIN accounted for 14.84% of all the renal biopsies received in our histopathology section within this period, with 74% cases presenting as acute renal failure. The mean age of our study group was 39 years, with the male-female ratio being 1:1.63. Drug-induced TIN accounted for 42% of the cases, making it the most common cause; 48% of the cases of drug-induced TIN were attributed to the use of nonsteroidal anti-inflammatory drugs. The other causes were immunological, infectious, metabolic, vascular, plasma cell dyscrasias, T-cell mediated and idiopathic. TIN is an important cause of acute renal failure, with drug-induced TIN constituting almost half the cases. These cases can be reversed if caught early, making renal biopsy a valuable modality in diagnosing TIN in cases of acute renal failure.