Tubulo-interstitial alterations in type I membranoproliferative glomerulonephritis. An investigation of 259 cases.

A total of 259 kidney biopsies with type I membranoproliferative glomerulonephritis (MPGN) were evaluated, and five grades of glomerular alterations were compared to the following four categories of tubulo-interstitial findings: no changes, interstitial fibrosis (IF), acute renal failure (ARF), ARF and IF combined. The tubulo-interstitial findings proved to be unrelated to the severity of the glomerular alterations. Severe glomerular lesions can be associated with completely normal interstitium and tubules. Conversely, low-grade glomerular lesions may be accompanied by severe tubular and/or interstitial lesions. When the renal cortical interstitium and tubules were normal, then creatinine and blood pressure values were within the normal range; however, these values were significantly elevated in the presence of IF and/or ARF. It is concluded from these findings that in MPGN type I the disturbance in the excretion function of the kidney is caused primarily by tubulo-interstitial changes rather than by glomerular lesions.