Morphologic Features of the Myopathy Associated With Chronic Renal Failure

Our previous studies indicate that impaired function of skeletal muscle limits the exercise tolerance of patients with end-stage renal failure who are either maintained on dialysis or undergo renal transplantation. To study the morphology of the condition, muscle biopsies were performed on eight patients with renal failure-associated myopathy. Control samples were taken from seven healthy athletes undergoing knee surgery and from five otherwise healthy but untrained subjects. Tissues were examined by routine light and transmission electron microscopy. Histochemical staining of frozen sections for myosin adenosine triphosphatase and quantitative computer-assisted morphometry of the fiber type and size was performed. The mean (± SD) size for type I fibers in patients was 61.2 ± 11.8 μm, while type II fibers measured 46.7 ± 11.4 μm. The mean percentage of type II fibers was 67% ± 12%. These values are within the normal population range and were not different from controls. Significant changes were found on light microscopy of patient samples. These included fiber splitting, internalized nuclei, nuclear knots, moth-eaten fibers, fiber degeneration and regeneration, increased content of lipid droplets, and fiber-type grouping. Electron microscopy showed a large variety of nonspecific abnormalities, including mitochondrial changes, Z-band degeneration, myofilament loss, and accumulation of intracellular glycogen. Ten of 12 control subjects showed no such changes; minor abnormalities were noted on both light and electron microscopy in the remaining two subjects. Muscle oxidative capacity (19.5 ± 5.1 μL O 2 /min) for patients with end-stage renal failure was not different from values for those who had undergone renal transplantation, but was lower than values found in trained athletes. Thus, patients undergoing maintenance hemodialysis for chronic renal failure have significant morphologic abnormalities in skeletal muscle. Such changes miaht exolain the impaired skeletal muscle function of these patients.