Changes of bone histology during maintenance hemodialysis at various levels of dialyzate Ca concentration.

Bone histology (iliac crest biopsies; undecalcified sections; micromorphometry) was studied by repeated biopsies in 19 patients on maintenance hemodialysis. Sampling error was assessed by taking two biopsies at one time. After an initial biopsy, patients were dialyzed either against 3.6 mEq Ca/l dialyzate or 3.9 mEq Ca/l dialyzate for 9-16 months before a second biopsy was taken. Bone histology failed to normalize irrespective of the dialyzate Ca concentration. Surface density of endosteal fibrosis diminished in a considerable proportion of the patients (9/19). Volumetric density of osteoid fell in 5 and rose in 4 of the patients.