Pyelonephritis and interstitial nephritis--clinical-pathological correlations

The relation between histological and clinical parameters were studied in 54 consecutive patients with acute interstitial nephritis or pyelonephritis without primary glomerular disorders, in all of whom percutaneous renal core biopsy had been performed.

Based on clinical criteria and without detailed knowledge of the appearance of the biopsy, the material was divided into 4 main groups: patients with septic and/or tubulotoxic conditions, hypersensitivity reactions (eosinophilic nephritis), ascending infections and other specified conditions.

The overall correlation between the histological and the clinical diagnoses was good, but there were large overlaps between the histological findings in 3 of the groups, making classification of individual cases difficult. The histological and paraclinical findings were poorly correlated. Histologically, ascending infections were characterized by the presence of leukocyte casts and an increased number of neutrophilic granulocytes.

The material justifies the present rough classification of the conditions mentioned above. By kidney biopsy, the interstitial conditions can be separated from glomerular and other conditions, but the biopsy offers little information about the clinical severity or the prognosis.