[Renal biopsy for diagnosis of interstitial nephritis].

Tubulo-interstitial nephropathy or nephritis is suggested if renal function is deteriorated and urinary findings are slight. In most cases, the daily urinary protein excretion is less than 1 g and macrohematuria is not present. Urinary excretion of N- acetyl-beta-glucosaminidase and beta 2-microglobulin is a good indicator for tubulo-interstitial damage. Acute renal failure is caused either by acute tubulo-interstitial nephritis or acute tubular necrosis. In either case, renal biopsy is essential for diagnosis and to characterize the renal damage. In the interstitium, edema and fibrosis are seen and lymphocytes, plasma cells, polymorpholeukocytes, and/or eosinophils infiltrate. Tubular basement membrane is sometimes disrupted and lymphocytes have infiltrated inside (tubulitis).