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Kidney Week

Abstract: SA-OR106

Potential for Recovery of Bone Density and Structure Following Renal Transplantation

Session Information

Category: Transplantation

  • 1902 Transplantation: Clinical

Authors

  • Ziolkowski, Susan, Stanford School of Medicine, Stanford, California, United States
  • Long, Jin, Stanford University, Palo Alto, California, United States
  • Goral, Simin, University of Pennsylvania, Bryn Mawr, Pennsylvania, United States
  • Zemel, Babette, University of Pennsylvania, Bryn Mawr, Pennsylvania, United States
  • Leonard, Mary B., Stanford School of Medicine, Stanford, California, United States
Background

Fracture rates increase early following renal transplant (RTxp) and then decline. The objective is to determine if trabecular and cortical bone mineral density (BMD) and cortical structure recover following RTxp treated with glucocorticoids (GC).

Methods

We enrolled 60 incident RTxp recipients, ages 20-60 yr, with DXA and peripheral quantitative CT (pQCT) scans at RTxp, 6, 12, and 24 months. Bone outcomes and DXA appendicular lean mass index (ALMI) were expressed as age and sex-specific Z-scores using concurrent controls. Regression models identified correlates of change for bone outcome Z-scores.

Results

58 and 53 RTxp completed the 12 and 24 month visit, respectively. At transplant, DXA total hip, femoral neck, and ultradistal radius BMD, and pQCT trabecular and cortical BMD, and cortical thickness BMD Z-scores were lower in RTxp vs. controls (all p<0.05). Prednisone was typically tapered to a maintenance dose of 5 mg/day by 4 weeks. During the first 6 months, DXA spine and pQCT trabecular BMD decreased significantly (e.g. trabecular BMD Z from -0.53 to -0.60) then were unchanged through 24 months. Radius 1/3rd BMD was stable but ultradistal BMD Z-scores decreased from baseline onwards. Greater GC exposure was associated with decreases in DXA spine and ultradistal radius BMD and pQCT trabecular BMD Z-scores (all p<0.01). Cortical BMD Z-scores increased across 24 months (from -0.51 to -0.33, p<0.01) in association (p = 0.02) with decreasing PTH. Endosteal circumference increased and cortical thickness decreased progressively over 24 months (both <0.01). DXA total hip and femoral neck BMD Z-scores were unchanged during the first 6 months, then increased marginally. ALMI Z-scores increased but were not associated with changes in bone outcomes. Gains in cortical BMD were associated with gains in total hip and femoral neck BMD (p<0.01). Renal function, physical activity and mineral metabolites were not associated with bone outcomes.

Conclusion

RTxp is associated with early loss of trabecular bone without subsequent recovery on low dose GC. Cortical BMD recovers in association with decreases in PTH levels and may explain the marginal increase in hip BMD. Given that cortical thinning progresses following RTxp, strategies are needed to preserve cortical structure in CKD.

Funding

  • NIDDK Support