Development of chronic renal failure in patients with multiple myeloma.

Glomerulotubular disconnections at the immediate postglomerular segment of the proximal tubules, accounting for an impaired renal function, were demonstrated recently in several chronic nonglomerular renal disorders. To analyze the glomerulotubular junctions in Bence Jones cast nephropathy, paraffin blocks from the kidneys of nine deceased patients with myeloma and chronic renal failure on whom autopsies were performed were studied in serial sections. Kidneys from seven deceased patients without renal disease on whom autopsies also were done served as controls. For stereological estimations, the percentages of patent and sclerosed glomerular profiles, the relative volume fractions, and the absolute volumes of the interstitium, tubules, and glomeruli were determined. In Bence Jones cast nephropathy, 96% of the glomerular profiles were patent, and the reconstruction of randomly chosen glomerulotubular junctions revealed that 84% of the patent glomeruli had normal tubular connections. There was an increased relative interstitial volume (fibrous tissue) and a decreased relative tubular volume. The absolute values indicated severe interstitial fibrosis, but not tubular atrophy. The results show that in contrast with other chronic nonglomerular nephropathies, chronic renal failure in Bence Jones cast nephropathy does not result from nephron disconnection at the immediate postglomerular segment of the proximal tubules. The main factor responsible for the decrease in renal function appears to be the progressive severe fibrosis of the interstitium.