Elevated bone aluminum content in dialysis patients without osteomalacia

Determination of trace elements and calcium in bone of the human iliac crest by atomic absorption spectrometry

A rapid and reliable analytical method for the determination of trace elements in human bone by atomic absorption spectrometry is reported. Calcium was determined to estimate the homogeneity of samples. Human bone from the iliac crest was obtained at autopsy of adult subjects. Before analysis samples were decomposed by microwave digestion and acid digestion in a Parr bomb. Zinc, rubidium, strontium, calcium and iron were determined by flame atomic absorption spectrometry (FAAS) and aluminium, copper and lead by electrothermal atomic absorption spectrometry (ETAAS) at optimum measurement conditions. The results for the two digestion procedures agreed for zinc, rubidium and calcium within +/-5%, for copper within +/-7% and for strontium, iron, aluminium and lead within +/-10%. The repeatability of measurement (R.S.D.) for determination of calcium and trace elements after microwave digestion and acid digestion in a Parr bomb was tested in one representative autopsy bone sample by six parallel determinations. It was found to be better than +/-5% either for microwave digested samples or samples digested in a Parr bomb, for all elements determined by FAAS and ETAAS techniques. The accuracy of the applied digestion procedures was checked by analysis of trace elements in NIST SRM 1486 Bone Meal reference material. Good agreement of the results with certified values was obtained for both digestion procedures. The microwave procedure developed for digestion of small amounts of sample was applied in trace elements analysis of bone biopsy samples from dialysis patients.

Southwestern Internal Medicine Conference: bone disease in kidney failure: diagnosis and management

Recent technologic and therapeutic advances have improved the life of the patient with end-stage renal disease. High efficiency and high-flux hemodialyzer membranes have shortened the time required to dialyze, and recombinant erythropoietin has all but eliminated anemia as a major cause of morbidity, but the problem of renal osteodystrophy remains. The following discussion examines the spectrum of bone and joint disease in the patient with end-stage renal disease. The diagnostic and therapeutic strategies currently being tried in the management of these disorders are discussed.

Detection of subtle aluminum-related renal osteodystrophy

We compared the sensitivity of aurin tricarboxylic acid (ATA) or acid solochrome azurine (ASA) for detecting bone aluminum histochemically in 87 biopsy specimens obtained between 1983 and 1987 from 84 patients receiving dialysis therapy. Two consecutive biopsy sections were stained, one with ATA and the other with ASA, and then interpreted independently by two experienced observers. Three groups were established: group 1 (N = 61) had positive results of both ATA and ASA staining, group 2 (N = 25) had negative ATA but positive ASA sections, and group 3 (N = 1) had negative results of both ATA and ASA. No significant differences existed between groups 1 and 2 for age of the patients or serum calcium or immunoreactive parathyroid hormone levels. Patients in group 1 had significantly higher bone aluminium content (110 versus 61 micrograms/g dry ash weight), higher serum aluminum levels (151 versus 26 ng/ml), and longer duration of dialysis (85 versus 30 months) than did patients in group 2. Bone biopsy diagnoses (group 1 versus group 2) included low-turnover bone disease, 8 versus 7; osteomalacia, 26 versus 0; mixed uremic bone disease, 10 versus 1; hyperparathyroidism, 12 versus 14; and mild uremic bone disease, 5 versus 4. On the basis of ATA staining, 7 of 15 patients with low-turnover and 1 of 11 patients with mixed uremic bone disease may have been incorrectly diagnosed as having non-aluminum-related bone disorders. The levels of bone and serum aluminum were lower in group 2 than in group 1 but still much higher than normal.(ABSTRACT TRUNCATED AT 250 WORDS)

Resistance to recombinant human erythropoietin due to aluminium overload and its reversal by low dose desferrioxamine therapy

Seventeen severely anaemic and transfusion-dependent haemodialysis patients with a haemoglobin less than 7 g/dl were treated with recombinant human erythropoietin (r-Hu-EPO). Aluminium toxicity was diagnosed by a positive desferrioxamine (DFO) test and bone biopsy. Seven out of eight patients without aluminium toxicity responded to r-Hu-EPO therapy. Similarly all patients with aluminium toxicity (n = 4) but pre-treated with standard dose of DFO prior to r-Hu-EPO therapy responded but none of the patients with untreated aluminium toxicity (n = 5) responded to r-Hu-EPO therapy. In order to achieve adequate response in these patients, r-Hu-EPO and DFO had to be given in combination. The dose of desferrioxamine used to reverse r-Hu-EPO resistance was less and also used for a short time. We therefore confirm r-Hu-EPO resistance owing to aluminium overload and report its successful and safe reversal with low dose DFO therapy.

Clinical and histologic features of iron-related bone disease in dialysis patients

Forty-eight dialysis patients undergoing bone biopsy were analyzed for clinical history, blood biochemical values, bone histologic findings, bone aluminum content (BAC), bone iron content (BIC), bone iron stores, and histochemical staining of bone aluminum and bone iron. Four patients had significant trabecular bone iron staining alone; eight patients had significant bone iron and bone aluminum staining; 13 patients had significant bone aluminum staining alone; and 23 patients showed no significant bone aluminum or iron staining. Patients with significant bone iron staining were younger (37.4 +/- 5.3 years v 53.2 +/- 2.3 years, P less than 0.01, mean +/- SEM) and were more likely to be anephric (P less than 0.001) and to have a history of prior renal transplantation (P less than 0.10). The 12 patients with significant bone iron staining had received more blood transfusions than those without bone iron staining (96 +/- 22.8 U v 22 +/- 5.8 U, P less than 0.005). Patients with bone iron accumulation had higher levels of serum ferritin (3,594 +/- 1,138.4 micrograms/L [ng/mL] v 265 +/- 60.1 micrograms/L, P less than 0.01) and lower levels of immunoreactive parathyroid hormone (iPTH) (349 +/- 150 microLEq/mL v 1,801 +/- 397 microLEq/mL [386 +/- 166 pmol/L v 1,990 +/- 439 pmol/L], P less than 0.005). BIC was also higher in these patients (1,008 +/- 149 micrograms iron/g bone v 300 +/- 46.5 micrograms iron/g bone, P less than 0.001) and higher than normal BIC (256 +/- 44.2 micrograms iron/g bone, eight normals). Bone marrow iron stores were positively related to serum ferritin levels (P less than 0.01) and trabecular bone iron staining (P less than 0.10). All 13 patients with osteomalacia demonstrated significant bone aluminum staining; seven of these patients demonstrated concomitant significant iron staining. Fourteen of 15 patients with severe hyperparathyroidism showed no significant iron or aluminum staining. Our data indicate that iron will probably not accumulate within bone until all other storage sites (eg, bone marrow) are fully saturated. The presence of lower levels of iPTH in iron-overloaded patients raises the possibility that iron overload may induce a state of relative hypoparathyroidism. The most important determinant for the presence of osteomalacia seems to be the presence of significant aluminum staining. No specific bone histologic finding was related to the presence of bone iron staining, but the rarity of isolated significant bone iron staining makes it difficult to evaluate bone histologic diagnoses that might be solely attributable to iron.

Aluminum and chronic renal failure: sources, absorption, transport, and toxicity

In normal subjects the gastrointestinal tract is a relatively impermeable barrier to aluminum with a low fractional absorption rate for this metal ion. Aluminum absorbed from the gastrointestinal tract is normally excreted by the kidneys; in the presence of impaired renal function aluminum is retained and accumulates in body tissues. Aluminum-containing medications are given, by mouth, to patients with chronic renal failure as phosphate-binding agents for the therapeutic control of hyperphosphatemia. Patients with chronic renal failure are also exposed to aluminum in domestic tap-water supplies used either for drinking or, in those on dialysis treatment, in the preparation of their dialysate. In patients with end-stage chronic renal failure, particularly in those on treatment by hemodialysis, the accumulation of aluminum in bone, brain, and other tissues is associated with toxic sequelae. An increased brain content of aluminum appears to be the major etiological factor in the development of a neurological syndrome called either "dialysis encephalopathy" or "dialysis dementia"; an increased bone content causes a specific form of osteomalacia. An excess of aluminum also appears to be an etiological factor in a microcytic, hypochromic anemia that occurs in some patients with chronic renal failure on long-term treatment with hemodialysis. The various mechanisms involved in the toxic phenomena associated with the accumulation of aluminum in body tissues have not been clearly defined but are the subject of extensive investigations.

Deferoxamine and coated charcoal hemoperfusion to remove aluminum in dialysis patients

We studied the in vitro and in vivo characteristics of aluminum (Al) removal by coated charcoal hemoperfusion (HP) in combination with intravenous deferoxamine (DFO). DFO enhanced the clearance of Al by HP in vitro after 180 minutes of perfusion with a solution containing 403.3 +/- 14.0 ng/ml of Al at 150 ml/min. The Al clearance was 139 +/- 1.0 ml/min with DFO and 49 +/- 10.0 ml/min (P less than 0.001) without DFO. Addition of DFO enhanced in vitro Al removal from 5.5 +/- 0.9 mg to 10.0 +/- 1.2 mg (P less than 0.05). During our in vivo studies, an HP device was in series in the dialysis circuit after a Cuprophan hemodialyzer. Eight patients with Al toxicity were studied on twelve occasions. Patients received DFO (40 mg/kg) 40 hours before the study. The total Al clearance with the combined hemodialysis (HD) and HP devices was higher than that obtained by the dialyzer alone at 30 minutes (62 +/- 4.9 ml/min vs. 25 +/- 2.5 ml/min, P less than 0.02) and after 180 to 210 minutes (32 +/- 3.0 ml/min vs. 19 +/- 2.9 ml/min, P less than 0.02). After 120 minutes the Al clearance by the HP device alone was significantly lower than the initial Al clearance by HP. Combined HD plus HP removed 2.9 +/- 0.4 mg of Al, whereas the total removal of Al by HD alone was 1.5 +/- 0.3 mg (P less than 0.01).

Cortical v trabecular bone aluminum in dialyzed patients

Differences among measurement of cortical and trabecular bone aluminum (AI) have been observed. Furthermore, its relationship to bone histology has been variable. In order to clarify these points, we have evaluated measurements of bone AI in relation to the source of AI and bone lesion in 25 hemodialysis patients. All patients were dialyzed in the same unit since commencement of dialysis and treated by the same physician. Age of the patients ranged from 29 to 66 years; mean duration of dialysis was 6.6 +/- 3.5 years. Dialysate water has been treated by reverse osmosis since 1980. Bone biopsy was performed in all patients after double tetracycline labeling. AI was measured biochemically in cortical bone (bCAI) and histochemically in trabecular (TAI) and cortical bone (CAI). Mean serum AI (36 +/- 21 micrograms/L) and bCAI (59 +/- 44 micrograms/g) were increased. There were significant correlations between: cortical AI and (1) serum AI (r = 0.71, p less than 0.001); (2) duration of dialysis with softened water (AI content, 55 +/- 21 micrograms/L, r = 0.65, P less than 0.001) but not with total duration of dialysis; and (3) AI ingested since commencement of dialysis (r = 0.57, P less than 0.01). Trabecular AI was not correlated with any of these parameters. None of cortical AI measurements were correlated with bone formation rates (BFR), osteoblastic surfaces (ObS), and resorption surfaces (RS) determined on trabecular bone. However, trabecular AI was inversely correlated with BFR (P less than 0.01) and ObS (P less than 0.05). Serum parathyroid hormone (PTH) was positively correlated with BFR (P less than 0.001) and RS (P less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Aluminum and bone disorders: with specific reference to aluminum contamination of infant nutrients

Aluminum (Al) impairment of bone matrix formation and mineralization may be mediated by its direct effect on bone cells or indirectly by its effect on parathyroid hormone and calcium metabolism. Its toxic effects are proportional to tissue Al load. Al contamination of nutrients depends on the amount of Al present naturally in chemicals or from the manufacturing process. Intravenous calcium, phosphorus, and albumin solutions have high Al (greater than 500 micrograms/L), whereas crystalline amino acid, sterile water, and dextrose water have low Al (less than 50 micrograms/L) content. Enteral nutrients including human and whole cow milk have low Al, whereas highly processed infant formulas with multiple additives, such as soy formula, preterm infant formula, and formulas for specific disorders are heavily contaminated with Al. Healthy adults are in zero balance for Al. The gastrointestinal tract excludes greater than 95% of dietary Al, and kidney is the dominant organ for Al excretion. However, even with normal renal function, only 30-60% of an Al load from parenteral nutrition is excreted in the urine, resulting in tissue accumulation of Al. The risk for Al toxicity is greatest in infants with chronic renal insufficiency, recipients of long term parenteral nutrition, i.e., no gut barrier to Al loading, and preterm infants with low Al binding capacity. The rapid growth of the infant would theoretically potentiate Al toxicity in all infants, although the critical level of Al loading causing bone disorders is not known. To minimize tissue burden, Al content of infant nutrients should be similar to "background" levels, i.e., similar to whole milk (less than 50 micrograms/L).

Erosive spondyloarthropathy in long-term dialysis patients: relationship to severe hyperparathyroidism

We describe the development of a destructive, erosive spondyloarthropathy in three long-term dialysis patients (mean duration of dialysis, 96 months). In all three patients, the lesions caused symptomatic vertebral pain and developed during a period of only a few months. All patients had extremely elevated levels of immunoreactive parathyroid hormone, and two patients had evidence of severe hyperparathyroidism on bone biopsy specimens. Two patients who underwent subtotal parathyroidectomy had rapid relief of symptoms and no further radiographic evidence of progression of the spondyloarthropathy. The third patient refused subtotal parathyroidectomy and had pronounced progression of the destructive spondyloarthropathy in the cervical spine. The limited experience of others, along with our currently reported findings, strongly suggests that hyperparathyroidism plays a major role in the development of this disorder. Erosive spondyloarthropathy is increasingly recognized in long-term dialysis patients and may be a unique clinical and radiographic manifestation of severe hyperparathyroidism in this population.

Results of subtotal parathyroidectomy in hemodialysis patients

In 61 hemodialysis patients undergoing subtotal parathyroidectomy, there was a good correlation between the preoperative serum immunoreactive parathyroid hormone value (iPTH) and the weight of parathyroid tissue removed surgically (p less than or equal to 0.001). Postoperatively, iPTH decreased rapidly from an initial mean (+/- SD) of 2,928 +/- 1,600 muleq/ml and remained at 365 +/- 296 muleq/ml at last follow-up of patients still undergoing hemodialysis (normal, less than 50 muleq/ml). Of six patients who had recurrent hyperparathyroidism (10 percent of total), three required a second subtotal parathyroidectomy. Aluminum-related osteomalacia eventually developed in six patients with bone biopsy-proven hyperparathyroidism before parathyroidectomy. Nine patients with severe fracturing bone disease and hypercalcemia preoperatively but without clear evidence of hyperparathyroidism did not show a favorable response to subtotal parathyroidectomy (high mortality within 28 months, persistence of hypercalcemia, and symptomatic bone disease). Thus, subtotal parathyroidectomy can benefit patients with clearly established severe progressive hyperparathyroidism not responsive to medical therapy but is contraindicated in patients with low iPTH values and no bone biopsy evidence of severe hyperparathyroidism.

Response to aluminum in parenteral nutrition during infancy

The response to aluminum loading from parenteral nutrition (PN) solutions was determined in 20 infants with gestational ages 29 to 41 weeks and birth weights 880 to 3630 gm. Mean duration of PN was 43 days (range 5 to 175 days). Ten infants received a high Al load (from an experimental high calcium- and phosphorus-containing PN solution, with a measured Al content of 306 +/- 26 micrograms/L (mean +/- SE), n = 11), for up to 6 weeks. Ten infants received a lower Al load (from standard Ca-P solutions, measured Al content 144 +/- 16 micrograms/L, n = 11). Five infants received PN with a low Al load for longer than 6 weeks. The mean urine Al/creatinine (Cr) ratio (micrograms/mg) increased threefold, from 0.3 +/- 0.09 to 0.97 +/- 0.17 during PN in the entire group (P less than 0.001), and was significantly higher in infants who received greater Al loading (P less than 0.001). There was no significant difference between preterm and term infants in the rate of change in urine Al/Cr during the study. Urine Al was calculated to account for less than 50% of Al load. During the study, serum Al concentrations ranged from 6 to 318 micrograms/L (median 37 micrograms/L, compared with the median 18 micrograms/L for normal infants and children). Serum Al concentrations were not significantly changed during the study, or between infants in high or lower Al loading groups. Vertebrae from autopsy of two infants who received the lower Al containing PN for 71 and 152 days, respectively, stained positive for Al at the bone mineralization front. Thus, currently used PN solutions are contaminated with Al, urine Al concentration is higher with higher Al loading, and is not different in term and preterm infants. We suggest that renal elimination of Al in infants is incomplete, as assessed by lower urine Al excretion versus load, elevated serum Al concentration, and bone deposition of Al.