Quantitative ultrasound of the calcaneus and dual X-ray absorptiometry of the lumbar spine in assessment and follow-up of skeletal status in patients after kidney transplantation

Bone loss after kidney transplantation is a significant complication of immunosuppressive treatment leading to a high prevalence of bone fracture in these patients. The purpose of this study was to determine the usefulness of quantitative ultrasound (QUS) of the calcaneus in comparison with dual X-ray absorptiometry (DXA) of the lumbar spine in determining bone status and mineral changes in patients in the first 6 months after transplantation. Forty-six patients participated in the study (25 men and 21 women; age range 26–62 years, 102±66 months previously on dialysis). They were treated with cyclosporine, methylprednisolone, mycophenolate mofetil, and basiliximab. The 6-month cumulative steroid dose was 24.9±3.7 mg/kg body weight. Calcaneal QUS (Sahara, Hologic, Waltham, Mass.) and DXA (Hologic QDR 4500) of the lumbar spine were done in all patients within 3 weeks after transplantation and 6 months thereafter. Bone mineral density (BMD) of the lumbar spine measured by DXA decreased from 0.892±0.137 to 0.837±0.126 g/cm² (p<0.0001) and the T score decreased from 1.84±1.29 standard deviation (SD) to 2.35±1.19 SD (p<0.0001) in the first 6 months after transplantation. The QUS parameters of the calcaneus were broadband ultrasound attenuation (BUA), speed of sound (SOS), and quantitative ultrasound index (QUI). The QUS parameters did not change significantly after the first 6 months. All QUS parameters correlated significantly with DXA BMD of the lumbar spine immediately after transplantation and 6 months thereafter. Significant decrease of the lumbar spine BMD in the first 6 months after transplantation was not accompanied by significant changes of calcaneal QUS parameters. The calcaneal QUS does not reflect bone mineral changes occurring in the lumbar spine and could not be a substitute for a direct-site DXA of the lumbar spine in the early period after kidney transplantation.