RESUMEN
With the purpose of establishing the clinicopathologic correlation in pyelonephritis and to discard other interstitial nephrites, with present day morphologic criteria we analysed 63 casos that had been diagnosed as pyelonephritis, following Weiss and Parker's histologic criterion. The clinicopathologic diagnosis of pyelonephritis was confirmed in 12 cases; all of them showed obstructive uropathy and in most of them, there was chronic renal failure. Interstitial nephritis was established in 27 cases, all of them showing septicemia and almost half of the cases showed acute renal failure. Other 20 cases showed tubulointerstitial nephritis secondary to different types of glomerulopathies, fetal glomerulosclerosis, dysplasias, nephrophthisis, radiation nephritis and renal infarct. In 4 cases, the study of sections finer than the original, showed absence of histopathologic lesions. The results of the present study point out the main causes of confusion with the pathological diagnosis of pyelonephritis, the necessity to investigate predisposing uropathy in patients with urinary infection and stresses the importance to establish correlation with clinical and laboratory findings in cases with tubulointerstitial lesions.