Bone disease in long-term renal transplant recipients with severe osteopenia: a cross-sectional study

Clinical predictors of incipient vertebral fractures and bone mineral density in kidney transplant patients

PURPOSE

Kidney transplant recipients are prone to metabolic bone diseases and consequent fractures. This study aimed to evaluate the incidence of incipient vertebral fractures, osteopenia, osteoporosis, and the clinical factors associated with incipient vertebral fractures in a group of kidney transplant patients.

METHODS

Two hundred sixty-four patients (F/M 124/140, 45.3 ± 13 years) who had undergone kidney transplantation in tertiary care centers were included. Vertebral fractures were assessed semiquantitatively using conventional thoracolumbar lateral radiography in 202 of the patients.

RESULTS

Vertebral fractures were observed in 56.4% (n = 114) of the study group. The frequency of osteoporosis was 20.0% (53 of 264 patients), and osteopenia was 35.6% (94 of 264 patients). Bone mineral density (BMD) levels were in the normal range in 40.3% (n = 46) of the subjects with vertebral fractures. It was in the osteoporotic range in 20.1% (n = 23) and the osteopenic range in 40.3% (n = 46). Vertebral fractures were associated with age, duration of hemodialysis, BMI, and femoral neck Z score (R² 37.8%, p = 0.027).

CONCLUSION

As incipient vertebral fractures can be observed in patients with normal BMD levels in kidney transplant recipients, conventional X-ray screening for vertebral fractures may be beneficial for a proper therapy decision of metabolic bone disease in kidney transplant recipients.

Changes in Bone Histomorphometry after Kidney Transplantation

BACKGROUND AND OBJECTIVES

Over the past decade, the management of CKD-mineral and bone disorder has changed substantially, altering the pattern of bone disease in CKD. We aimed to evaluate the natural history of kidney bone disease in contemporary kidney transplant recipients and patients on dialysis.

DESIGN, SETTINGS, PARTICIPANTS, & MEASUREMENTS

Sixty one patients on dialysis who were referred to kidney transplantation participated in this prospective cohort study during November 2009 and December 2010. We performed baseline bone biopsies while the patients were on dialysis and repeated the procedure in 56 patients at 2 years after kidney transplantation or 2 years after baseline if transplantation was not performed. Measurements of mineral metabolism and bone turnover, as well as dual energy x-ray absorptiometry scans, were obtained concurrently.

RESULTS

A total of 37 out of 56 participants received a kidney transplant, of which 27 underwent successful repeat bone biopsy. The proportion of patients with high bone turnover declined from 63% at baseline to 19% at 2 years after kidney transplantation, whereas the proportion of those with low bone turnover increased from 26% to 52%. Of 19 participants remaining on dialysis after 2 years, 13 underwent successful repeat biopsy. The proportion of patients remaining on dialysis with high bone turnover decreased from 69% to 31%, and low bone turnover increased from 8% to 38%. Abnormal bone mineralization increased in transplant recipients from 33% to 44%, but decreased in patients remaining on dialysis from 46% to 15%. Trabecular bone volume showed little change after transplantation, but low bone volume increased in patients remaining on dialysis. Bone mineral density did not correlate with histomorphometric findings.

CONCLUSIONS

Bone turnover decreased over time both in patients remaining on dialysis and in kidney transplant recipients. Bone mineral density and bone biomarkers were not associated with bone metabolism changes detected in bone biopsy specimens.

Lumbar Spine Fusion Surgery in Solid Organ Transplant Recipients Is Associated With Increased Medical Complications and Mortality

STUDY DESIGN

Retrospective database review.

OBJECTIVE

To characterize the outcomes of solid organ transplant (SOT) patients after one- or two-level lumbar fusion surgery.

SUMMARY OF BACKGROUND DATA

Over the past decade advances in SOT patients have improved graft survival. As such, this patient population is increasingly eligible for elective surgery such as lumbar fusion procedures to improve mobility and quality of life. However, the outcomes of spine surgery in this population are not well defined.

METHODS

Data from the full 100% Medicare sample between 2005 and 2014 were used for the study. Patients were included if they had an elective one- or two-level lumbar spine fusion and previous history of renal, heart, liver, or lung SOT patients during this period. SOT patients were compared to non-SOT patients with respect to baseline characteristics, 90-day medical complications, 1-year rate of revision surgery, and 1-year mortality.

RESULTS

There were 961 patients in the transplant cohort and 258,342 in the non-SOT cohort. Seventy-seven percent of the SOT patients had prior renal transplant. SOT patients had a longer length of stay (P < 0.001), and a higher 30-day readmission rate compared to non-SOT patients (P =  < 0.001). In addition, SOT patients experienced a 23.8% rate of 90-day postoperative major medical complications and 3.0%, 1-year mortality, significantly larger than respective rates in the control population (P < 0.001). One-year infection, revision surgery rates, and wound dehiscence were not significantly different between the two cohorts.

CONCLUSION

Spine surgery is associated with significant medical complications and 1-year mortality in the SOT population. Although there may be a substantial benefit from lumbar fusion in the SOT population, judicious patient selection is of paramount importance.

LEVEL OF EVIDENCE

3.

Vascular calcification, bone and mineral metabolism after kidney transplantation

The development of end stage renal failure can be seen as a catastrophic health event and patients with this condition are considered at the highest risk of cardiovascular disease among any other patient groups and risk categories. Although kidney transplantation was hailed as an optimal solution to such devastating disease, many issues related to immune-suppressive drugs soon emerged and it became evident that cardiovascular disease would remain a vexing problem. Progression of chronic kidney disease is accompanied by profound alterations of mineral and bone metabolism that are believed to have an impact on the cardiovascular health of patients with advanced degrees of renal failure. Cardiovascular risk factors remain highly prevalent after kidney transplantation, some immune-suppression drugs worsen the risk profile of graft recipients and the alterations of mineral and bone metabolism seen in end stage renal failure are not completely resolved. Whether this complex situation promotes progression of vascular calcification, a hall-mark of advanced chronic kidney disease, and whether vascular calcifications contribute to the poor cardiovascular outcome of post-transplant patients is reviewed in this article.

Persistence of bone and mineral disorders 2 years after successful kidney transplantation

BACKGROUND

Studies that have conducted bone biopsies after kidney transplantation are scarce, and the results are conflicting.

METHODS

We evaluate the bone histomorphometry, in vitro proliferation, and alkaline phosphatase expression in osteoblasts isolated from bone biopsies from 27 kidney transplant patients. The patients had preserved renal function and were treated with the same immunosuppressive therapy, receiving a minimum dose of corticosteroids.

RESULTS

The biochemical analysis revealed that 41% of the patients presented with hypercalcemia, 26% presented with hypophosphatemia, and hypovitaminosis D was detected in 63%. The histomorphometric analysis showed a reduced trabecular number and increased trabecular separation, mineral apposition rate, and mineralization lag time, as well as higher osteoid surface, osteoblastic surface, resorption surface, and osteoclastic surface and a lower mineralizing surface, compared with the controls. Based on the TMV classification, bone turnover was normal in 48%, high in 26%, and low in 26% of patients. Bone mineralization was delayed in 48% of the patients, and 58% of the patients with hypovitaminosis D presented with delayed bone mineralization. Bone volume was low in 37% of the patients. The osteoblasts from patients exhibited a higher degree of proliferation compared with those from controls.

CONCLUSION

Eight-two percent of our patients presented with alterations in at least one of the TMV parameters. Persistence of hyperparathyroidism, hypovitaminosis D, and immunosuppressive drugs may have influenced osteoblast function, which would explain many of the bone alterations found in these patients.

Management of metabolic bone disease in kidney transplant recipients

Bone disease after kidney transplantation has a complex pathophysiology and heterogeneous histology. Pre-existing renal osteodystrophy may not resolve completely, but continue or evolve into a different osteodystrophy. Rapid bone loss immediately after transplant can persist, at a lower rate, for years to come. These greatly increase the risk of bone fracture and vertebral collapse. Hypovitaminosis D, hyperparathyroidism and hyperaluminemia may resolve after kidney transplant, but many patients have other risk factors of bone loss, such as steroids usage, hypogonadism, persistent hyperparathyroidism, poor allograft function, aging, and chronic diseases. Clinical management requires a comprehensive approach to address the underlying and ongoing disease processes. Successful prevention of bone loss has been shown with vitamin D analogues, bisphosphonates and calcitonin. Novel approaches to restore the normal bone remodeling and improve the bone quality may be needed in order to effectively decrease bone fractures in kidney transplant recipients.

Mineral and bone disorder after renal transplantation: a review

Chronic kidney disease-mineral bone disorder is a common clinical picture encountered in patients with end-stage renal disease and is the result of additive pathophysiological processes. Renal transplantation remains the treatment of choice for these patients, especially as advances in this field have allowed for enhanced allograft survival. However, with increasing success of renal transplantation has come a greater appreciation of some of its subsequent complications, such as posttransplantation bone disease. Recently, persistent hyperparathyroidism and osteopenia-osteoporosis have been given specific attention. Traditionally, persistent hyperparathyroidism has been treated with parathyroidectomy, although the role that calcimimetics may play in the future is promising. Newer aspects to medical management of osteopenia-osteoporosis, such as the efficacy of bisphosphonate therapy and early steroid withdrawal, are becoming apparent and some of the newer drugs for the treatment of osteoporosis are yet to be investigated in this subgroup of patients.

Conversion of immunosuppressive monotherapy from cyclosporin a to tacrolimus reverses bone loss in rats

Tacrolimus is used for transplant patients with refractory graft rejection and those with intolerance to cyclosporin (CsA), without the disfiguring adverse effects frequently attributed to CsA therapy. Since we have shown that CsA-associated bone loss can also affect alveolar bone, the purpose of this study was to evaluate the effects of conversion of monotherapy from CsA to tacrolimus on alveolar bone loss in rats. Groups of rats were treated with either CsA (10 mg/kg/day, s.c.), tacrolimus (1 mg/kg/day, s.c.), or drug vehicle for 60 and 120 days, and an additional group received CsA for 60 days followed by conversion to tacrolimus for a further 60-day period. Bone-specific alkaline phosphatase (BALP), tartrate-resistent acid phosphatase (TRAP-5b), calcium (Ca(2+)), interleukin (IL)-1beta, IL-6, and tumor necrosis factor alpha (TNF-alpha) concentrations were evaluated in the serum. Analyses of bone volume, bone surface, number of osteblasts, and osteoclasts were performed. Treatment with CsA for either 60 or 120 days was associated with bone resorption, represented by lower bone volume and increased number of osteoclasts; serum BALP, TRAP-5b, IL-1beta, IL-6, and TNF-alpha were also higher in these animals. After conversion from CsA to tacrolimus, all the altered serum markers returned to control values in addition to a significant increase of bone volume and a lower number of osteoclasts. This study shows that conversion from CsA to tacrolimus therapy leads to a reversal of the CsA-induced bone loss, which can probably be mediated by downregulation of IL-1beta, IL-6, and TNF-alpha production.