Renal biopsy findings and clinicopathologic correlations in nephropathia epidemica

A series of 126 adult patients with a serologically confirmed diagnosis of nephropathia epidemica (NE) were studied during the acute phase of the disease. In 86 cases, renal biopsy was performed. The severity of renal failure correlated slightly with blood inflammatory parameters and the degree of hematuria but not with the amount of proteinuria. The degree of hematuria correlated inversely with the level of thrombocytopenia. The most common histopathologic lesion was acute tubulointerstitial nephritis. Interstitial edema and inflammatory cell infiltrations were most usually present, followed by tubular epithelial and luminal alterations. Slight glomerular mesangial changes were present in 25% of the biopsy specimens. Except for hemorrhage in the outer renal medulla, the histologic lesions were relatively mild and unspecific. Interstitial hemorrhage should remind a pathologist of the possibility of NE. Tubular, interstitial and glomerular histologic damage were but vascular lesions were not associated with the clinical severity of renal failure. Glomerular alterations did not relate to the amount of urine protein excretion. Correlations, however, were so weak that in clinical work renal biopsy is usually not indicated for determination of the severity of renal failure in NE. Intrinsic renal events are probably important in the development of renal failure in NE.