Advances in the evaluation of bone health in kidney transplant patients

Prevalence of Musculoskeletal and Metabolic Disorders in Kidney Transplant Recipients: A Systematic Review and Meta-Analysis

Introduction

Musculoskeletal disorders could be associated with metabolic disorders that are common after kidney transplantation, which could reduce the quality of life of patients. The aim of this study was to assess the prevalence of both musculoskeletal and metabolic disorders in kidney transplant patients.

Methods

MEDLINE, CINAHL, Cochrane Library, EMBASE and Web of Science were searched from their inception up to June 2023. DerSimonian and Laird random-effects method was used to calculate pooled prevalence estimates and their 95% confidence intervals (CIs).

Results

21,879 kidney transplant recipients from 38 studies were analysed. The overall proportion of kidney transplant patients with musculoskeletal disorders was 27.2% (95% CI: 18.4-36.0), with low muscle strength (64.5%; 95% CI: 43.1-81.3) being the most common disorder. Otherwise, the overall proportion of kidney transplant patients with metabolic disorders was 37.6% (95% CI: 21.9-53.2), with hypovitaminosis D (81.8%; 95% CI: 67.2-90.8) being the most prevalent disorder.

Conclusion

The most common musculoskeletal disorders were low muscle strength, femoral osteopenia, and low muscle mass. Hypovitaminosis D, hyperparathyroidism, and hyperuricemia were also the most common metabolic disorders. These disorders could be associated with poorer quality of life in kidney transplant recipients.

Systematic Review Registration

https://www.crd.york.ac.uk/prospero/, identifier [CRD42023449171].

Bone Mineral Density Changes in Long-Term Kidney Transplant Recipients: A Real-Life Cohort Study of Native Vitamin D Supplementation

Vitamin D insufficiency has been associated with reduced bone mineral density (BMD) in kidney transplant patients (KTRs). However, the efficacy of vitamin D supplementation on BMD remains poorly defined, especially for long-term KTRs. We aimed to investigate the effect of native vitamin D supplementation on the BMD of KTRs during a 2-year follow-up. Demographic, clinical, and laboratory data were collected. BMD was evaluated with standard DEXA that was performed at baseline (before vitamin D supplementation) and at the end of study period. BMD was assessed at lumbar vertebral bodies (LV) and right femoral neck (FN) by a single operator. According to WHO criteria, results were expressed as the T-score (standard deviation (SD) relative to young healthy adults) and Z-score (SD relative to age-matched controls). Osteoporosis and osteopenia were defined as a T-score ≤ -2.5 SD and a T-score < -1 and a > -2.5 SD, respectively. Based on plasma levels, 25-OH-vitamin D (25-OH-D) was supplemented as recommended for the general population. Data from 100 KTRs were analyzed. The mean study period was 27.7 ± 3.4 months. At study inception, 25-OH-D insufficiency and deficiency were recorded in 65 and 35 patients. At the basal DEXA, the percentage of osteopenia and osteoporosis was 43.3% and 18.6% at LV and 54.1% and 12.2% at FN, respectively. At the end of the study, no differences in the Z-score and T-score gains were observed. During linear mixed model analysis, native vitamin D supplementation was found to have a negative nitration with Z-score changes at the right femoral neck in KTRs (p < 0.05). The mean dose of administered cholecalciferol was 13.396 ± 7.537 UI per week; increased 25-OH-D levels were found (p < 0.0001). Either low BMD or 25-OH-vitamin D concentration was observed in long-term KTRs. Prolonged supplementation with 25-OH-D did not modify BMD, Z-score, or T-score.

The Non-invasive Diagnosis of Bone Disorders in CKD

Abnormal bone metabolism is an integral part of the chronic kidney disease-mineral bone disorder (CKD-MBD). For several reasons, the difficult bone compartment was neglected for some time, but there has been renewed interest as a result of the conception of bone as a new endocrine organ, the increasing recognition of the cross-talk between bone and vessels, and, especially, the very high risk of osteoporotic fractures (and associated mortality) demonstrated in patients with CKD. Therefore, it has been acknowledged in different guidelines that action is needed in respect of fracture risk assessment and the diagnosis and treatment of osteoporosis in the context of CKD and CKD-MBD, even beyond renal osteodystrophy. These updated guidelines clearly underline the need to improve a non-invasive approach to these bone disorders in order to guide treatment decisions aimed at not only controlling CKD-MBD but also decreasing the risk of fracture. In this report, we review the current role of the most often clinically used or promising biochemical circulating biomarkers such as parathyroid hormone, alkaline phosphatases, and other biochemical markers of bone activity as alternatives to some aspects of bone histomorphometry. We also mention the potential role of classic and new imaging techniques for CKD patients. Information on many aspects is still scarce and heterogeneous, but many of us consider that it is indeed time for action, recognizing our definitely limited ability to base certain treatment decisions only on our current non-comprehensive knowledge.

Behavior of Calcium, Phosphorus, and Parathormone Before Transplantation and in Months 1, 3, 6, 9, and 12 After Transplantation

BACKGROUND

Bone mineral disease after transplantation persists and is an issue that must be addressed owing to the cardiovascular impact it presents. The objective of this study is to present the behavior of calcium, phosphorus, and parathormone (PTH) before renal transplantation (RT) and throughout the 12 months after transplant surgery.

METHODS

A longitudinal observational study of RT patients was performed from 2013 to 2017 in 2 renal transplant units in Mexico. In total, 1009 records of patients with RT were analyzed. Calcium, phosphorus, and PTH levels were studied before transplantation and for 12 months after. Central tendency and dispersion were measured, the difference of means was established with chi square or student t tests, and the significant value of P was set at <.05. We also used the SPSS statistical package, version 25.

RESULTS

Phosphorus had a median pre-RT of 5.73, which decreased to 2.8 in the first month post-transplant and then increased to 3.41 at 12 months post-RT. The median PTH, on the other hand, started at 420.60 and decreased to 67.45. Calcium began at 9.04 and hit a plateau of 9.58 during month 12 after the surgical event.

CONCLUSIONS

Of the 3 biochemical parameters evaluated, phosphorus was the one that most corrected itself after transplantation. Despite a tendency toward hypophosphatemia in the first month after transplantation, it began to normalize from month 6 on. Meanwhile, calcium was the biochemical value that changed the least after transplantation.