Diagnosis and management of bone disorders in chronic renal failure and dialyzed patients

Wide variation in reference values for aluminum levels in children

BACKGROUND

Some parents are requesting aluminum testing in their children with developmental issues. Although aluminum can be measured in plasma, serum, or urine, there is scant scientific information about normal ranges. We sought to determine the basis for laboratory reference ranges and whether these ranges are applicable to children.

METHODS

From texts, published lists, and Internet sources, we obtained the names of 10 clinical laboratories that perform aluminum testing. Contact was made by telephone or e-mail, or Internet sites were viewed to obtain information regarding the establishment of aluminum reference ranges and testing methods in biological samples. Seven laboratories provided supporting literature that was reviewed regarding details of the study populations.

RESULTS

For laboratories using the atomic absorption spectrometry method, aluminum reference ranges varied from <5.41 μg/L to <20 μg/L (serum), <7.00 μg/L to 0 to 10 μg/L (plasma) and 5 to 30 μg/L (urine). For those using the inductively coupled plasma mass spectroscopy methodology, ranges varied from 0 to 6 μg/L to <42 μg/L (serum), 0 to 10 μg/L to 0 to 15 μg/L (plasma), and 0 to 7 μg/L to 5 to 30 μg/L (urine). None of the reference ranges are known to be derived from studies of healthy children, but relied instead on small studies of adult populations, adult dialysis patients, workers, or sick children on aluminum-containing parenteral therapy.

CONCLUSIONS

Aluminum reference ranges provided by laboratories are widely divergent, may not represent "normal" ranges of a healthy population, especially children, and thus it is difficult to interpret serum or urine aluminum ranges clinically. Further studies of aluminum in children are warranted and should be considered as part of the Centers for Disease Control and Prevention Biomonitoring Project.

Long-term fracture risk following renal transplantation: a population-based study

Abnormal bone metabolism is a recognized complication of end-stage renal disease, but fracture risk following renal transplantation has not been well quantified. We followed the 86 Olmsted County, Minnesota, residents who underwent initial renal transplantation in 1965-1995 for 911 person-years (median, 10.6 years per subject) in a retrospective cohort study. Fractures, and possible risk factors, were assessed through review of each subject's complete community medical records. Altogether, 117 fractures were observed during follow-up extending to 33 years. The cumulative incidence of any fracture at 15 years was 60% versus 20% expected ( P<0.001). There was a significantly increased risk of fractures generally [standardized incidence ratio (SIR), 4.8; 95% CI, 3.6-6.4] and vertebral (SIR, 23.1; 95% CI, 12.3-39.6) and foot fractures (SIR, 8.4; 95% CI, 5.1-12.9) especially. Age at first transplantation, renal failure due to diabetes, pancreas transplantation, peripheral neuropathy, peripheral vascular disease and blindness were all associated with overall fracture risk. In a multivariate analysis, however, only age and diabetic nephropathy were independent predictors of fracture risk generally, while higher activity status was protective. Diabetes was the only independent predictor of lower limb fractures, whereas age and osteoporosis history predicted vertebral fractures. Cumulative corticosteroid dosage was not associated with increased fracture risk in this analysis. Despite the fact that our patients had few risk factors for preexisting bone disease attendant to postmenopausal osteoporosis, prior corticosteroid use or renal osteodystrophy, these data indicate that renal transplantation is associated with a significant increase in fracture risk among unselected patients in the community. Diabetic patients, particularly, experience excess lower limb fractures. Patients and their care providers should be aware of this elevated fracture risk, which continues long-term.

Relationship between serum phosphorus levels and various outcome measures in adult hemodialysis patients

OBJECTIVE

To compare three different mean serum phosphorus ranges on outcomes related to the control and treatment of hyperparathyroidism (HPTH), to nutritional status, and to quality of life (QOL) in adult hemodialysis (HD) patients.

DESIGN

Patients were grouped based on the mean of five monthly phosphorus levels achieved during the study period. Group 1 included patients whose mean phosphorus levels over the period was <6.0 mg/dL (n = 24); group 2 averaged between 6.0 and 6.9 mg/dL (n = 14); and group 3 averaged >7.0 mg/dL (n = 16). Descriptive comparisons were made between phosphorus groups.

PATIENTS

Fifty-four stable, adult HD patients participated voluntarily.

MAIN OUTCOME MEASURES

Intact-parathyroid hormone (iPTH), calcium x phosphorus product (Ca x P), and change in iPTH, albumin (alb), total protein (tpro), weight (wt) and body mass index (BMI), and scores on a QOL survey. Baseline physical and lab characteristics.

RESULTS

No difference was found between phosphorus levels of <6.0 mg/dL and levels of 6.0 to 6.9 mg/dL in iPTH, Ca x P levels allowing safe calcitriol therapy, nor response to calcitriol treatment. Patients with phosphorus levels >7.0 mg/dL had midstudy iPTH greater than phosphorus levels <6.0 mg/dL. Otherwise the three groups did not differ significantly in iPTH levels. Phosphorus levels 6.0 to 6.9 mg/dL was associated with lowest wt and BMI, but alb and tpro did not differ between the phosphorus groups. Phosphorus levels of >7.0 was associated with highest creatinine levels and youngest age. Subjects in the phosphorus levels of <6.0 mg/dL gp were more likely than the 6.0 to 6.9 mg/dL gp to describe their diet as sufficient and, at baseline, were more likely to relate diet to QOL.

CONCLUSION

Comparison of three levels of serum phosphorus on indicators of outcome in the control and treatment of secondary hyperparathyroidism showed no significant difference in outcome between phosphorus levels of <6.0 mg/dL and phosphorus levels 6.0 to 6.9 mg/dL. However, the data suggests that phosphorus levels of >7.0 mg/dL may relate to significantly higher iPTH and unacceptable Ca x P levels. There were no differences between the groups, suggesting less favorable outcome at any of the three phosphorus levels regarding nutritional status or QOL in this small group of stable, adult HD patients.

Renal osteodystrophy of the cervical spine: neurosurgical implications

Renal osteodystrophy describes the changes in bone physiology seen in renal failure. Traditionally, these changes resulted in mild neurological sequelae that were effectively managed medically. Despite the often severe destruction seen on x-ray, surgical therapy has not been reported extensively. With increasing numbers of long-term hemodialysis survivors, however, a newly recognized erosive spondyloarthropathy with extensive bony destruction is seen more frequently. These changes can mimic the radiographic appearance of osteomyelitis, not an uncommon sequela of hemodialysis patients; therefore, this diagnosis must be considered. Although renal osteodystrophy can be seen throughout the spine, reports of significant cervical spine involvement are uncommon. We present our experience with six cases of renal osteodystrophy of the cervical spine requiring surgical intervention for instability or cord compression. Osteomyelitis was present in two of the patients. The pathophysiology and radiographic characteristics of renal osteodystrophy and the incidence of osteomyelitis are discussed. Fusion techniques, including the use of anterior and posterior internal and external stabilization, are presented. These patients represent a therapeutic challenge for the neurosurgeon, given the underlying bone pathology.

Management of the oral and maxillofacial surgery patient with end-stage renal disease

Chronic renal failure (CRF) is the consequence of a multitude of diseases that cause permanent destruction of the nephron. Concurrent with renal failure are a host of changes affecting the homeostatic functioning of the individual. This report outlines the pathophysiology of CRF and highlights its effects on surgical manipulation of the oral and maxillofacial region in this patient population. In addition, some of the common physical findings and alterations in blood chemistries frequently observed in these patients are discussed.