Low bone mass and high incidence of fractures after successful simultaneous pancreas-kidney transplantation

Abstract

Background. Simultaneous pancreas-kidney transplantation successfully restores normoglycaemia and corrects uraemia in insulin-dependent diabetes mellitus patients with end-stage renal failure due to diabetic nephropathy. Low bone turnover and cortical osteopenia are often associated with the diabetic state and corticosteroid-induced bone loss, predominantly trabecular, is expected post-transplantation. Little is known, however, about the resultant long-term effects of successful simultaneous pancreas-kidney transplantation on bone mass and consequent fracture rate. Methods. We studied bone and mineral metabolism, bone densitometry (using dual X-ray absorptiometry), and fracture prevalence in a cross-sectional design in 31 IDDM patients at least 12 months (mean 40 ± 23 months) after successful simultaneous pancreas-kidney transplantation. Results. All patients were insulin-independent and mean creatinine clearance was 64 ± 21 ml/min. Secondary hyperparathyroidism, probably multifactorial, was found in 55% of the patients. Increased bone turnover as suggested by elevated osteocalcin concentrations was present in 45% of the patients. Twenty-three per cent of patients had a significant decrease in bone mass (T score < -2.5 SD) at the predominantly trabecular lumbar spine sites. In contrast, 58% demonstrated a similarly low bone mass at the femoral neck, where cortical bone is prevalent. Forty-five per cent of patients had documented vertebral (mostly asymptomatic) and non-vertebral fractures. Conclusion. Our findings suggest that low bone mass is prevalent after successful simultaneous pancreas-kidney transplantation, and that this is associated with a high incidence of fractures, representing a cause for concern with regard to long-term morbidity. Contrary to the predominant trabecular bone loss expected with corticosteroid excess, cortical bone loss was prevalent in our patients, possibly due to pre-existing diabetic state and persistent hyperparathyroidism.