Histological renal osteodystrophy, and 25 hydroxycholecalciferol and aluminum levels in patients on continuous ambulatory peritoneal dialysis

Serum 25-hydroxyvitamin D status was associated with brachial-ankle pulse wave velocity and mortality among peritoneal dialysis patients

BACKGROUND/OBJECTIVES

To investigate the correlation between serum 25-hydroxyvitamin D (25(OH)D) and brachial-ankle pulse wave velocity (baPWV) and mortality among peritoneal dialysis (PD) patients.

SUBJECTS/METHODS

We retrospectively reviewed the data of 269 PD patients in our center from January 1, 2013, to December 31, 2018. Subjects were divided into groups according to serum 25(OH)D level based on a cut-off of 20 ng/ml. The general linear regression model was employed to explore the correlation between 25(OH)D and baPWV. The correlation between 25(OH)D and mortality was examined in Cox proportional hazards models.

RESULTS

The mean (±SD) concentration of serum 25(OH)D was 17 (±7.2) ng/ml. Using linear regression analysis, and after adjusting for possible confounders, serum 25(OH)D concentration was found to be negatively associated with baPWV(β = -0.35, p < 0.001). Multivariate analysis showed that lower 25(OH)D level was significantly associated with higher total mortality in PD patients(< 20 ng/ml vs. ≥ 20 ng/ml; HR, 2.27; 95% CI, 1.04-4.93; P = 0.04)(as a continuous variable; HR, 0.94; 95% CI, 0.90-0.98; P = 0.01).

CONCLUSIONS

Serum 25(OH)D concentration was a significant factor associated with baPWV and mortality among patients with PD. Further studies with larger sample sizes will be needed to confirm this correlation.

Relation of Serum 25-Hydroxyvitamin D Status with Skeletal Muscle Mass and Grip Strength in Patients on Peritoneal Dialysis

The aim of this study was to investigate the association of serum 25-hydroxyvitamin D (25(OH)D) with skeletal muscle mass (SMM) and grip strength in patients on peritoneal dialysis. In this single center retrospective study, a total of 113 incident peritoneal dialysis patients (65 men, 48 women) were included. Serum concentrations of 25(OH)D were measured through radioimmunoassay. Hypovitaminosis was classified when the level of serum 25(OH)D was <20 ng/mL. SMM was assessed through bioelectrical impendence analysis, whereas grip strength was assessed through handgrip dynamometer. On the basis of expert consensus of the Asian Working Group for Sarcopenia, low muscle mass was defined as relative skeletal mass index (RSMI)<7.0 kg/m² for men and <5.7 kg/m² for women. The general linear and noncondition logistical regression model were employed to explore the association between vitamin D and both muscle mass and grip strength. The mean serum 25(OH)D level was 19.3(±8.4) ng/mL. Compared with 25(OH)D<20 ng/mL, the mean values of SMM, appendicular skeletal muscle mass (ASM), ASMI, and grip strength were higher for ≥20 ng/mL. Subjects (25(OH)D<20 ng/mL) had a greater proportion of low SMM (55.8%) and low grip strength (66.4%). After adjusting for multiple factors, serum 25(OH)D was positively associated with grip strength (β=0.18, p=0.009), ASM (β=0.14, p<0.001), and RSMI (β=0.07, p<0.001); 25(OH)D<20 ng/mL was significantly associated with low grip strength (OR=2.97, 95% CI: 1.17-7.55), and low SMM (OR=2.73, 95% CI: 1.15-6.45). The present study demonstrated a positive association between serum vitamin D status and skeletal muscle mass and grip strength in patients on peritoneal dialysis.

Renal Osteodystrophy in Patients on Continuous Ambulatory Peritoneal Dialysis: A Five Year Study

The clinical, biochemical, radiological and histopathological data related to renal osteodystrophy were extracted from the computer records of 81 patients who had been treated by continuous ambulatory peritoneal dialysis (CAPD) for more than two years. Paired bone histopathology was available in 45 of these patients.

The majority maintained normal serum ionised and total calcium concentrations, while mean serum phosphate concentration ranged from 1.68 to 1.80 mmol/l. Serum parathyroid hormone concentrations fell significantly in those with high values at the start of CAPD. Five patients underwent parathyroidectomy. Mean serum aluminium concentrations were higher than normal healthy controls and the levels rose further after the addition of aluminium-containing phosphate binders (ACPB).

Of the patients with histological evidence of secondary hyperparathyroidism, 82% showed improvement on repeat biopsy. Nine, who had no evidence of osteitis fibrosa at the beginning of CAPD, remained free of bone disease during the study period. Osteomalacia was present in two patients at the onset of CAPD and developed in three more, two of them after parathyroidectomy. Except for one patient, all those with osteomalacia improved after the addition of alfacalcidol and continuation of CAPD. This last patient died with evidence of aluminium deposition in his bones.

We conclude that when used as clinically indicated, CAPD, with the addition of calcium carbonate, phosphate binders and alfacalcidol, achieves good control of renal osteo dystrophy in the majority of patients.

Calcium Kinetic Studies in Patients on Capd: Improvement of Secondary Hyperparathyroidism without Concomitant Improvement of Calcium Turnover

Objective

An association between the development of low turnover osteopathy and the form of dialysis treatment, that is, continuous ambulatory peritoneal dialysis (CAPD), has been described. To examine the effect of a year-long CAPD treatment on calcium (Ca) turnover, 12 patients were studied prior to and one year after initiation of CAPD treatment with a dialysate calcium of 1.75 mmol/L.

Design

A prospective analysis.

Setting

Academic teaching hospital dialysis unit.

Patients

Twelve patients with an average age of 54.8 years (range: 23 76 years) at commencement of dialysis and after 13 months of CAPD treatment.

Measurements

Calcium kinetic studies were performed using two calcium isotopes: 45Ca as an oral tracer and 47Ca as an intravenous tracer. Measurements of plasma and whole body activities were performed over a four week period. From these measurements, kinetic parameters describing calcium turnover in different compartments were studied. These measurements were repeated after a mean time of 13.4 months. Patients were not treated with vitamin D, but received aluminum and calcium -containing phosphate binders, in order to keep inorganic phosphate below 2.0 mmol/L and calcium within the normal range.

Results

After one year on CAPD, serum levels of calcium increased from 2.2 mmol/L to 2.35 mmol/L. Inorganic phosphate also increased from 1.4 mmol/L to 1.9 mmol/L, despite increased use of oral phosphate binders. Serum levels of intact parathyroid hormone (i PTH) decreased from 51.2 pmol/L to 28.3 pmol/L. Alkaline phosphatase did not change, nor did serum levels of vitamin D. Despite improvement of serum iPTH levels and better control of serum calcium, the kinetic parameters describing calcium turnover in the different calcium pools did not improve. In addition, the calcium retention of bone remained below normal range and did not rise. Perhaps more importantly, the relationship between Ca efflux and Ca retention did not change. While Ca retention remained low, plasma Ca efflux was normal. This imbalance was seen at the beginning of CAPD and did not change under CAPD.

Conclusion

These data demonstrate that, after one year of CAPD treatment without vitamin D treatment, calcium turnover did not improve, despite a significant fall in serum iPTH levels. Studies on a larger number of patients are warranted to verify these results.

Aluminum Hyoroxioe-Inouceo Osteomalacia, Encephalopathy ANO Hyperaluminemia in CAPO. Treatment with Oesferrioxamine

We present the clinical course of a patient who has been treated with CAPD since 1979. He developed dialysis encephalopathy and fracturing osteomalacia, and was found to have a serum aluminum concentration of 560 μg/L. Treatment with desferrioxamine over a six month's period reduced his serum aluminum concentration to a non-toxic level, and his symptoms abated. One year after his initial encephalopathy this patient has a normal EEG, the bone fractures have healed, and serum aluminum concentration is 38 μg/ L. Apparently the hyperaluminemia was due to the ingestion of prescribed aluminum hydroxide.

Prevalence and Correction of 25(OH) Vitamin D Deficiency in Peritoneal Dialysis Patients

Background

Peritoneal dialysis (PD) patients are at risk for 25(OH) vitamin D deficiency due to effluent loss in addition to traditional risk factors.

Objectives

To measure 25(OH) vitamin D deficiency in prevalent PD patients, to evaluate a replacement dose, and to determine the effects of correction.

Methods

25(OH) vitamin D levels were drawn on prevalent PD patients. Patients deficient in 25(OH) vitamin D were given ergocalciferol, 50 000 IU orally once per week for 4 weeks. Patients scored muscle weakness, bone pain, and fatigue on a scale of 0 (none) to 5 (severe). Serum calcium, phosphate, parathyroid hormone (PTH), and 25(OH) vitamin D, and 1,25(OH)2 vitamin D levels were obtained before and after treatment.

Results

25(OH) vitamin D levels were measured in 29 PD patients. Deficiency (<15 ng/mL) was found in 28/29 (97%); 25/29 (86%) had undetectable levels (<7 ng/mL). One course of ergocalciferol corrected the deficiency in all but 1 patient, who required a second course. Scores for muscle weakness and bone pain fell from pre- to posttreatment ( p < 0.001). 1,25(OH)2 vitamin D levels rose post ergocalciferol (from 20 to 26 pg/mL, n = 20, p = 0.09). Serum calcium, phosphate, and PTH levels did not change with ergocalciferol.

Conclusions

Most PD patients had marked 25(OH) vitamin D deficiency, which was readily and safely corrected with one course of 50000 IU ergocalciferol, having no effect on serum calcium, phosphorus, or PTH, but complaints of muscle weakness and bone pain decreased. A prospective, placebo-controlled double-blinded study is needed to determine whether replacement of 25(OH) vitamin D is beneficial in PD patients.

Effect of Oral Calcidiol Treatment on Its Serum Levels and Peritoneal Losses

Objectives

To evaluate calcidiol serum levels in a group of continuous ambulatory peritoneal dialysis (CAPO) patients and the effect of oral calcidiol treatment on serum levels and peritoneal losses.

Study design

Twenty patients (13 female, 7 male) were studied for 12 –60 months. Their ages ranged 22 72 years (mean 46±15). Serum calcidiol, total protein and urea were determined at baseline and after the administration per os of 0.133 mcg/day of calcidiol for 10 days. At the same time, calcidiol and total protein were measured in peritoneal effluent at baseline and at 5,10, and 40 days after starting this treatment.

Results

A significant and direct correlation between the calcidiol dialysis/plasma ratio and the peritoneal protein losses was found, both before and 40 days after calcidiol administration when calcidiol serum levels were the lowest. As calcidiol serum levels rose to the normal range in the course of the study, peritoneal losses of this metabolite increased slightly and correlated with calcidiol serum levels and urea mass transfer coefficient (MTC); the significant correlation between calcidiol serum levels and peritoneal protein losses disappeared.

Conclusions

When serum calcidiol levels are low, calcidiol peritoneal losses in patients on CAPO correlate with protein peritoneal losses. However, when serum calcidiollevels rise, the calcidiol peritoneal losses correlate with calcidiol serum levels and urea MTC, and not with protein peritoneal losses.

Effects of Subcutaneous Calcitriol Administration on Plasma Calcium An D Parathyroid Hormone Concentrations in Continuous Ambulatory Peritoneal Dialysis Uremic Patients

Objective

To ascertain whether the parathyroid hormone (PTH) secretion of continuous ambulatory peritoneal dialysis (CAPD) uremic patients could be suppressed by repeated subcutaneous injections of calcitriol (CLT).

Design

Nonrandomized prospective study with weekly evaluation.

Setting

Hospital CAPD clinic.

Patients

Seven uremic CAPD patients with signs of severe hyperparathyroidism.

Interventions

Patients were treated with CLT (2 μg), injected subcutaneously three times a week, on alternate days over a period of 8 weeks.

Measurements

Plasma PTH, ionized calcium (Ca), serum phosphate (Pi), and alkaline phosphatase (AP) were assayed before the start of CLT therapy and weekly thereafter.

Results

The average basal PTH was 349±26 pg/mL (mean ±SD).ltfell significantly by the fifth week to 158±20, then leveled off. Analysis of the individual data, however, revealed that only 5 of 7 patients had a significant decrease in plasma PTH. Basal Ca was ±.02 mmol/L; it increased continuously throughout the study, significantly by the fourth week, reaching a level of 1.33±0.3 mmol/L at the sixth week, then declined slightly. In those patients with significantly decreased PTH, there was an inverse correlation between PTH and the corresponding Ca levels.

Conclusions

In some CAPD patients subcutaneous administration of CLT significantly suppresses PTH. This effect is mainly mediated via an increase in ionized calcium, but a direct inhibitory effect of the vitamin on parathyroid glands cannot be excluded.

Vitamin D and Vitamin-D-Binding Protein Kinetics in Patients Treated with Continuous Ambulatory Peritoneal Dialysis (CAPD)

Serum and dialysate levels of 25-hydroxycholecalciferol (25-0HD3), 1,25 dihydrox ycholecalciferol (1,25(0H)2D3), and vitamin-D-binding protein (DBP) were measured in 14 patients undergoing continuous ambulatory peritoneal dialysis (CAPD). Serum levels of 25-0HD3 and DBP were within normal range (29.1 ± 22.9 nmollL and 5.9 ± 1.1 μmol/L, respectively). Serum levels of 1,25-(0H)2D3 were subnormal in all «16 pmol/L) but one. In 5 patients, dialysate concentrations of 25-0HD3 were 2.3 ± 0.9 nmol/L, the rest had levels <1.0 nmol/L. Small quantities of 1,25-(0H)2D3 were found in the dialysate effluents.

DBP could be detected in the dialysate in all patients (0.24 ± 0.06 μmol/L). Mass transfer (MT) of 25-0HD3 and DBP were respectively -10.4 ± 8.3 nmol/24 h and -1.46 ± 0.46 μmol/24 h. Peritoneal clearances of 25-0HD3 and DBP were low (0.40 ± 0.37 mL/min and 0.18 ± 0.06 mL/ min, respectively.

We conclude that CAPD leads to losses of 25-0HD3 and DBP. However, the peritoneal loss of DBP is well compensated and does not result in serum deficiency. Serum 25-0HD3 levels did not correlate with time on CAPD.

Renal Osteodystrophy and the Status of Aluminum and Other Trace Metals in CAPD Patients: A Panel Review

Most reports indicate that in patients on CAPD, hyperparathyroid bone disease progresses, while osteomalacia improves. With 1.5g% Dianeal, and when dialysate Ca is 7mg%, peritoneal mass transfer of calcium is positive, i.e., it is absorbed from the solution, while with hypertonic solutions it is less positive or even negative. Daily phosphorus removal by CAPD is insufficient to control serum phosphorus, hence CAPD patients require phosphate binders and/or phosphate restriction. Peritoneal phosphorus removal is greater with hypertonic than with isotonic solutions.

In patients on CAPD, the loss of substantial amounts of D-binding protein and 25(OH)DJ into the dialysate, produces a gradual decrease in plasma 25(OH)D levels. Similarly, these patients have low 1,25(OH)D2 DJ levels and, hence, should receive vitamin D or its analogues.

Unlike hemodialysis, CAPD results in a significant removal of PTH, with a peritoneal clearance of 1.5 ml/min. However, despite an estimated daily loss of 13.5% of the circulating PTH, there probably is not a significant effect on plasma PTH levels, which usually respond to changes in serum Ca. Levels of the intact PTH molecule provide a better index of hyperparathyroidism than do levels of its COOH-terminal fragment.

With regard to investigation and treatment, one should measure serum ionic calcium rather than total calcium, even if the latter is corrected for total protein. The minimal dialysate calcium should be 7 mg/dl and for hypertonic solutions, perhaps it should be higher (7.5–8.0 mg%). Total serum calcium should be maintained at 10.2–10.7 mg/dl (ionized calcium of 5.1–5.5 mg/dl); adjunctive use of active forms of vitamin D and prevention of aluminum intoxication may prevent progressive bone disease in CAPD, and existing bone disease may heal.

Whereas there are enough data supporting the connection of aluminum toxicity and osteomalacia in hemodialysis patients, data concerning the incidence of osteomalacia and its relationship to aluminum in CAPD patients are scarce. Apparently CAPD removes aluminum more efficiently than hemodialysis. CAPD patients are less likely to develop osteomalacia because the dialysate aluminum content is low and these patients tend to require lower doses of phosphate binder.

There are no extensive studies on trace element deficiencies or excess in patients on CAPD. These patients may be more susceptible to deficiencies of trace elements which are protein bound. Desferoxamine may be effectively used for the treatment of patients with either aluminum or iron overload.

The Sigmoidal Parathyroid Hormone-Ionized Calcium Curve and the Set Point of Calcium in Hemodialysis and Continuous Ambulatory Peritoneal Dialysis

A high Incidence of adynamic bone disease not related to aluminum Intoxication has been reported In continuous ambulatory peritoneal dialysis (CAPD). Since reduced parathyroid hormone (PTH) secretion may predispose to adynamic bone, we Investigated whether parathyroid gland sensitivity may be depressed In CAPD in comparison with hemodialysis (HD). Thus we determined parathyraid function by the evaluation of the PTH-ionized calcium (ICa) relationship, which was obtained Inducing hypocalcemia and hypercalcemia In 19 CAPD and 18 HD patients with biochemical and histological evidence of mild (MILD) or severe (OF) hyperparathyroidism, but negative stainable bone aluminum. Either CAPD or HD patients with OF showed a shift to the right of the sigmoidal PTH-ICa curve in comparison with patients with MILD, greater set point of calcium, and maximal PTH stimulation and Inhibition. The PTH-lCa curve and the other parathyraid function parameters were not different in CAPD and HD patients within the same bone histological group. In conclusion, our data document that parathyroid gland activity Is stimulated either in CAPD and HD patients with OF, but is not depressed in CAPD patients in comparison with HD patients.

Can Low-Calcium Peritoneal Dialysis Solution Safely Replace the Standard Calcium Solution in the Majority of Chronic Peritoneal Dialysis Patients?

Objective

To evaluate the use of low-calcium solution as the standard solution in chronic peritoneal dialysis patients.

Design

Prospective long-term follow-up study over a one-year period.

Setting

University hospital.

Interventions

The change of the calcium concentration of the dialysate from 1.75 mmollL to 1.25 mmollL.

Main Outcome Measures

Serum calcium and phosphorus concentration and intact parathyroid hormone (iPTH).

Patients

Fifty normo and hypercalcemic patients using the standard 1.75 mmollL calcium solution.

Results

Serum ionized calcium (iCa) decreased significantly during the first six months, resulting in a significant increment of iPTH (baselinevalue: 0.9 79, median 9.4 pmollL; at six months: 1.1 -111, median 20.6 pmollL; p < 0.05). In 28 patients completing the study, iPTH remained significantly elevated, despite high normal iCa. At similar changes of iCa, patients with baseline iPTH > 20 pmollL showed a significantly higher increase in iPTH than patients with low iPTH (24.0 vs 5.0; p < 0.01), despite a more than doubled dose of alfacalcidol and calcium carbonate (mean dose of 1580 increased to 3277 mg/day). During the follow-up, 21 episodes of hypercalcemia were observed. Phosphorus control was adequate.

Conclusions

Low-calcium solution cannot be used as a standard solution, especially in patients with iPTH levels indicating mild or severe hyperparathyroidism, because in these patients iPTH may rise further.

Risk Factors for Hyperaluminemia in Continuous Ambulatory Peritoneal Dialysis

The authors evaluated risk factors for hyperaluminemia and aluminum toxicity in 51 CAPD patients, who received aluminum-containing phosphate binders. Serum aluminum correlated with total intake of elemental aluminum after starting CAPD (p = 0.001), with aluminum intake in the previous six months (p = 0.001), with duration of CAPD (p = 0.003), and with serum phosphate (p = 0.05). Eight patients had elevated serum aluminum, but only one had clincial evidence of aluminum toxicity (he had been on hemodialysis with untreated water until he was changed to CAPD 30 months before the study). Although the incidence of clinical aluminum toxicity appears to be low, we conclude that the aluminum intake from aluminum-containing phosphate binders is a major factor in the evolution of hyperaluminemia and, potentially, aluminum toxicity in CAPD patients. We believe that alternative effective, phosphate binders are much needed.

It has been shown that tissue accumulation of aluminum in brain, bone and blood in uremic patients causes encephalopathy (I. 2), osteomalacia (3, 4), and anemia (5, 6). Clinically aluminum toxicity has been observed mainly in hemodialysis patients (1–6), although it has been reported in few cases before dialysis (7–9) and in those on continuous ambulatory peritoneal dialysis (10. II). The major cause of aluminum toxicity during hemodialysis has been transfer of aluminum from untreated water in the dialysate (1–5); this mechanism has tended to obscure the contribution of other factors, such as diet and drugs. Peritoneal dialysate contains a low concentration of aluminum (less than 15 μg/L) and there is a net removal of aluminum in the dialysate in those with serum aluminum levels within the reference range for dialysed uremics (11–13). Serial aluminum levels in CAPD patients not receiving aluminum -containing phosphate binders (ACPB) showed no significant change during a two-year follow-up (12, 14); this suggests that aluminum removal in the dialysate compensates for the failure of the kidney to excrete absorbed dietary aluminum in end-stage renal disease. Since the combination of CAPD and diet appears to have minimal influence on serum aluminum, this study was done to identify those factors which determine serum aluminum levels in CAPD patients, receiving aluminum-containing phosphate binders.

Vitamin D Deficiency in Chronic Kidney Disease: Recent Evidence and Controversies

Vitamin D (VD) is a pro-hormone essential for life in higher animals. It is present in few types of foods and is produced endogenously in the skin by a photochemical reaction. The final step of VD activation occurs in the kidneys involving a second hydroxylation reaction to generate the biologically active metabolite 1,25(OH)₂-VD. Extrarenal 1α-hydroxylation has also been described to have an important role in autocrine and paracrine signaling. Vitamin D deficiency (VDD) has been in the spotlight as a major public healthcare issue with an estimated prevalence of more than a billion people worldwide. Among individuals with chronic kidney disease (CKD), VDD prevalence has been reported to be as high as 80%. Classically, VD plays a pivotal role in calcium and phosphorus homeostasis. Nevertheless, there is a growing body of evidence supporting the importance of VD in many vital non-skeletal biological processes such as endothelial function, renin-angiotensin-aldosterone system modulation, redox balance and innate and adaptive immunity. In individuals with CKD, VDD has been associated with albuminuria, faster progression of kidney disease and increased all-cause mortality. Recent guidelines support VD supplementation in CKD based on extrapolation from cohorts conducted in the general population. In this review, we discuss new insights on the multifactorial pathophysiology of VDD in CKD as well as how it may negatively modulate different organs and systems. We also critically review the latest evidence and controversies of VD monitoring and supplementation in CKD patients.

Prevalence of 25(OH) vitamin D insufficiency and deficiency in pediatric patients on chronic dialysis

BACKGROUND

25(OH) Vitamin D [25(OH)D] is the major circulating form of vitamin D and the parameter used to reflect vitamin D status. Patients with chronic kidney disease (CKD) are likely to have low levels of 25(OH)D, and recent observations have linked suboptimal vitamin D status with adverse cardiovascular outcomes, inflammation, insulin resistance, and the rate of progression of renal insufficiency. Little is known about the magnitude of vitamin D deficiency in pediatric patients with stage 5 CKD on chronic dialysis.

OBJECTIVES

The aim of the present cross-sectional study was to assess the prevalence of abnormal vitamin D status in children on chronic dialysis.

METHODS

Serum 25(OH)D, 1,25(OH)2 vitamin D [1,25(OH)2D], calcium, phosphorus, and parathyroid hormone (PTH) were evaluated in 59 pediatric patients on chronic dialysis. Weekly renal Kt/V and creatinine clearance (CCr) were evaluated as parameters reflecting residual renal function. In these patients, serum 25(OH)D concentrations less than 10 ng/mL were considered deficiency and concentrations of 10 - 30 ng/mL were considered insufficiency.

RESULTS

Of the 59 pediatric patients (mean age: 14.4 ± 5.1 years), 51 (86.4%) were on peritoneal dialysis (PD), and 8 (13.6%) were on hemodialysis. Vitamin D deficiency was found in 32.2% of the patients (n = 19), and vitamin D insufficiency, in 50.8% (n = 30). Patients with serum 25(OH)D concentrations less than 30 ng/mL were older than those with normal 25(OH)D concentrations (15.4 ± 4.5 years vs 9.2 ± 5.1 years, p = 0.000). Patients with 25(OH) D concentrations less than 30 ng/mL had higher PTH levels than did those with normal 25(OH)D concentrations (349.5 ± 318.3 pg/mL vs 142.5 ± 116.9 pg/mL, p = 0.001). In the univariate analysis, there was no correlation between serum 25(OH)D and serum 1,25(OH)2D (r = 0.242, p = 0.064), calcium (r = 0.108, p = 0.415), phosphorus (r = -0.050, p = 0.706), or body mass index (r = -0.046, p = 0.729). In PD patients, serum 25(OH)D was positively correlated with weekly renal Kt/V (r = 0.385, p = 0.005) and CCr (r = 0.443, p = 0.001). In addition, serum 25(OH)D and serum albumin were positively correlated (r = 0.297, p = 0.035) in the PD patients.

CONCLUSIONS

The present study found a high prevalence of 25(OH)D deficiency and insufficiency in children on chronic dialysis. Serum 25(OH)D was associated with residual renal function in children on PD. Further studies to evaluate the consequences of vitamin D deficiency and the impact of therapeutic interventions are needed in pediatric CKD patients.

Risk factors and consequences of hyperaluminemia in a peritoneal dialysis cohort

BACKGROUND

Widespread Al toxicity is unusual today. In 2005, Canadian peritoneal dialysis (PD) centers reported widespread hyperaluminemia in patients using dialysates from one specific manufacturer. Our objectives were to evaluate risk factors related to Al accumulation and to assess its clinical consequences in patients from 2 centers.

METHODS

A retrospective closed cohort study was conducted in patients treated with PD in May 2005. A multivariate linear regression model was constructed to identify variables associated with a higher serum Al level in the exposed group at the moment of solution change. Using appropriate statistical methods, anemia and bone metabolism parameters were compared between the exposed and unexposed groups. Time to first peritonitis was estimated by the Kaplan-Meier method.

RESULTS

The study cohort included 87 Al-exposed patients and 95 unexposed patients. In the exposed group, serum Al at the moment of solution change was influenced by the length of exposure to Al-containing dialysates and by PD creatinine clearance; serum Al was inversely correlated with renal creatinine clearance. No consequences of Al accumulation were observed. No difference was observed in the time to first peritonitis between patients who switched manufacturers and those who remained with the original manufacturer.

CONCLUSIONS

Our results suggest that hyperaluminemia is directly related to the length and extent of exposure to Al-containing dialysates; residual renal function is protective against Al accumulation. Because the problem was detected rapidly, no clinical consequences of hyperaluminemia were observed in the study cohort.

Risk factors for renal osteodystrophy: a multivariant analysis

To assess the risk factors associated with renal osteodystrophy, we examined the database of 256 patients who were prospectively studied in three Toronto dialysis centers between October of 1987 and 1989. The potential risk factors examined included age, sex, type and duration of dialysis, type and dose of phosphate binders, vitamin D treatment, and history of diabetes mellitus, renal allograft failure, parathyroidectomy, and bilateral nephrectomy. All patients had undergone a bone biopsy and were categorized into one of four disease groupings: (1) osteitis fibrosa and mixed bone disease, (2) aluminum bone disease, (3) mild bone disorder, and (4) aplastic bone disorder. The mean (+/- SD) age of the patients at bone biopsy was 57 +/- 15 years, and 62% were men. Forty-five percent of patients were treated by hemodialysis and 55% by peritoneal dialysis. The mean duration of dialysis was 4 +/- 4 years. Twenty-five percent were also diabetic. The most common disorder was the aplastic (or "adynamic") bone disorder, found in 34% of patients. Aluminum bone disease was found in 27%, osteitis fibrosa or mixed bone disease in 27%, and mild bone disorder in 12% of patients. Cumulative intake of aluminum gels was associated with aluminum bone disease, whereas peritoneal dialysis with supraphysiologic calcium concentrations, ingestion of calcium carbonate, and diabetes mellitus were associated with both mild bone disorder and aplastic bone disorder. These three latter risk factors may be important in predisposing patients to a low bone turnover state through modulation of parathyroid hormone secretion.(ABSTRACT TRUNCATED AT 250 WORDS)

Free and total 1,25-dihydroxyvitamin D levels in subjects with renal disease

Patients with nephrotic syndrome and varying degrees of renal failure, including those on chronic hemo- and peritoneal dialysis, may have low serum concentrations of total 1,25-dihydroxyvitamin D [1,25(OH)2D]. However, it is unknown whether the true activity of 1,25(OH)2D is better reflected by the free 1,25(OH)2D fraction. We measured total 1,25(OH)2D, free 1,25(OH)2D, and vitamin-D-binding protein (DBP) in normal subjects (group A), subjects with moderate renal failure (group B), subjects on hemodialysis (group C), subjects on peritoneal dialysis (group D), and subjects with nephrotic syndrome (group E). The serum concentrations of total and free 1,25(OH)2D decreased with worsening renal function in groups A through C, with a high degree of correlation (r = 0.974, P less than 0.0001). Levels of DBP and the percent free 1,25(OH)2D remained constant in these groups. Patients on peritoneal dialysis and nephrotic patients had lower levels of DBP (203 +/- 14 micrograms/ml and 371 +/- 46 micrograms/ml, respectively) than normal subjects (436 +/- 33 micrograms/ml) and had significantly higher percent free 1,25(OH)2D (0.98 +/- 0.13% and 1.27 +/- 0.14%, respectively) compared to 0.63 +/- 0.03% (P less than 0.05). Thus, the loss of DBP in these patients correlated with a rise in the percent free 1,25(OH)2D. We conclude that levels of total 1,25(OH)2D are an accurate representation of 1,25(OH)2D status in normal subjects, subjects with renal insufficiency without nephrotic syndrome, and hemodialysis patients. In peritoneal dialysis and nephrotic patients, who lose DBP, measurements of free 1,25(OH)2D may be necessary in order to accurately assess 1,25(OH)2D status.

Aluminum accumulation during treatment with aluminum hydroxide and dialysis in children and young adults with chronic renal disease

BACKGROUND

The control of hyperphosphatemia is a major clinical problem in patients with chronic renal failure receiving regular dialysis treatment. Despite continuing concern about aluminum toxicity, aluminum-containing antacids are still used in many of these patients as phosphate-binding agents. Although maximal acceptable doses of aluminum hydroxide have been recommended, the safety and efficacy of these guidelines have not been evaluated.

METHODS

Seventeen children and young adults (mean [+/- SD] age, 14.1 +/- 3.7 years) undergoing regular peritoneal dialysis were randomly assigned to treatment with either aluminum hydroxide (n = 7; maximal dose, 30 mg per kilogram of body weight per day) or calcium carbonate (n = 10; dose range, 2.5 to 12 g per day, according to serum phosphorus levels). Aluminum retention was assessed by serial measurements of plasma aluminum, deferoxamine-infusion tests, and measurements of bone aluminum content during a mean (+/- SD) follow-up of 13 +/- 2 months. The evolution of bone disease was also evaluated.

RESULTS

Plasma aluminum levels and the increment in plasma aluminum after infusion of deferoxamine increased from base-line values in the patients treated with aluminum hydroxide, and aluminum-related bone disease developed in one patient. Serum phosphorus levels remained higher and serum calcium levels lower in the patients receiving aluminum hydroxide than in those receiving calcium carbonate. The skeletal lesions of secondary hyperparathyroidism improved in 7 of 10 patients receiving calcium carbonate but persisted or progressed in 6 of 7 patients given aluminum hydroxide (P less than 0.025).

CONCLUSIONS

Aluminum hydroxide is less effective than calcium carbonate as a phosphate-binding agent for the control of hyperphosphatemia and is associated with aluminum retention in children and young adults with chronic renal failure who are receiving dialysis therapy.

"High-dose" calcitriol for control of renal osteodystrophy in children on CAPD

High doses of calcitriol were used prospectively for 11 to 29 months to raise serum calcium levels in an effort to control renal osteodystrophy in 16 children undergoing CAPD. Serum Ca, P, iPTH and alkaline phosphatase were measured monthly; hand radiographs were obtained every six months, and a semiquantitative score of bone abnormalities was evaluated by two independent observers. During the study, serum Ca increased from 9.9 +/- 0.9 to 11.0 +/- 0.6 mg/dl (P less than 0.001); serum iPTH decreased by 113 +/- 131 microliter Eq/ml (P less than 0.005); serum P was unchanged; and serum alkaline phosphatase fell by 33 +/- 46% (P less than 0.02), 530 +/- 397 to 204 +/- 551 IU/liter. The radiographic score fell from 4.8 +/- 4.6 to 0.9 +/- 1.2 (P less than 0.005). The average and maximal doses of calcitriol were 0.61 +/- 0.37 and 0.95 +/- 0.56 microgram/day or 28 +/- 18 and 46 +/- 28 ng/kg body wt/day, respectively. Transient and asymptomatic hypercalcemia occurred in nine patients and two patients had reversible conjunctivitis in association with the hypercalcemia. Thus, "high dose" calcitriol prevented or controlled progression of hyperparathyroid bone disease in most pediatric CAPD patients. The failure to suppress PTH or reverse secondary hyperparathyroidism until the serum Ca rose to 10.5 to 11.0 mg/dl could reflect an increase in the "set point" for PTH suppression by serum calcium in many uremic children.

Plasma aluminum levels in pediatric dialysis patients: comparison of hemodialysis and continuous ambulatory peritoneal dialysis

Accumulation of aluminum occurs in children with renal failure and can cause anemia, disabling osteodystrophy, and encephalopathy. Effects on bone mineralization are of particular concern in pediatric patients with growth potential. We measured plasma aluminum levels in 36 patients on continuous ambulatory peritoneal dialysis (CAPD) and 22 on hemodialysis under surveillance at a single pediatric center. The levels were above normal in 35 and 21 patients, respectively, and the values correlated with the oral dose of aluminum-containing phosphate-binding medications (r = 0.57; P less than 0.001). Younger and smaller children had higher plasma aluminum levels and also received larger doses of oral aluminum-containing compounds. Mean plasma aluminum levels (57.2 +/- 52.8 and 48.7 +/- 32.1 micrograms/liter, respectively) and the daily oral doses of elemental aluminum (47.3 +/- 37.6 and 39.2 +/- 26.7 mg/kg, respectively) were not statistically different in patients on CAPD and those on hemodialysis. Plasma aluminum levels did not correlate with estimated cumulative oral intake of aluminum, total duration of dialysis, serum calcium and phosphorus concentrations, N-terminal parathyroid hormone levels, or transfusion requirements. Retention of aluminum is common in children undergoing dialysis, correlates with the amount of aluminum administered orally, and results in similar elevations of plasma aluminum with CAPD and hemodialysis. Younger and smaller children are at increased risk for accumulation of aluminum. Alternative methods for control of serum phosphorus are needed in children with end-stage renal disease.

The effects of intraperitoneal calcitriol on calcium and parathyroid hormone

Parathyroid suppression by intraperitoneal calcitriol (1,25(OH)2D3) during peritoneal dialysis. The purpose of this study was to determine if parathyroid hormone (PTH) suppression could be achieved by increasing calcium mass transfer (Ca MT) with high dialysate Ca (4 mEq/liter) or via intraperitoneal (i.p.) 1,25(OH)2D3 in patients undergoing continuous ambulatory peritoneal dialysis. Eleven patients were dialyzed for two months with standard Ca dialysate (3.5 mEq/liter) followed by two months with 4.0 mEq/liter Ca, then by three months of i.p. 1,25(OH)2D3. During the latter period, patients were randomized to groups whose dialysate contained either 3.5 mEq/liter or 4.0 mEq/liter Ca. We found that 4.0 mEq/liter Ca dialysate more than doubled Ca MT (37 +/- 17 mg/day to 84 +/- 6 mg/day) leading to a modest fall (P less than 0.05) in PTH levels (84 +/- 5.5% of controls). Ionized calcium levels did not change. With i.p. 1,25(OH)2D3, however, ionized calcium rose significantly (P less than 0.001) leading to a decline in PTH levels to 53.9 +/- 7.9% of control values. Serum 1,25(OH)2D3 levels rose from undetectable to 47.7 +/- 7.2 pg/dl (normal range 20 to 35). These studies indicate that increasing Ca MT using a 4.0 mEq/liter Ca dialysate leads to a small reduction in PTH concentrations. On the other hand, i.p. 1,25(OH)2D3 is well absorbed into the systemic circulation, raises ionized calcium levels, and leads to a marked suppression of PTH. Thus, i.p. 1,25(OH)2D3 may be a simple and effective means to suppress secondary hyperparathyroidism in patients undergoing CAPD.

Continuous ambulatory peritoneal dialysis and bone

We studied the effects of continuous ambulatory peritoneal dialysis (CAPD) on the histological manifestations of uremic bone disease. Twelve patients underwent bone biopsy immediately prior to and after one year of such treatment. Those with larger quantities of non-mineralized bone matrix (osteoid) experienced a reduction in relative osteoid volume, mean osteoid seam width, and total osteoid surface. Moreover, the use of time-spaced kinetic markers of mineralization (tetracycline) enabled us to demonstrate that CAPD usually decreased the amount of non-mineralized bone matrix by shortening mineralization lag time (that is, the interval from organic matrix deposition to its mineralization). The changes in the histomorphology appeared to occur independently of bone aluminum. These data indicate that CAPD generally enhances the mineralizing capacity of individual osteoblasts and suggests that such therapy is beneficial to the uremic skeleton.

Review: Renal osteodystrophy--pathogenesis and treatment

Histologic bone changes of osteitis fibrosa and osteomalacia are commonly present in patients with end-stage renal disease. Although many patients are not symptomatic from these bone changes, some patients are severely disabled. Altered metabolism of vitamin D, calcium, phosphorus, and parathyroid hormone occurs in renal failure and contributes to the development of uremic bone disease. This article reviews the current theories of pathogenesis and treatment of renal osteodystrophy. In addition, the clinical presentation, pathogenesis, and treatment of the various aluminum-associated osteomalacic syndromes in uremia are discussed.

Renal osteodystrophy--pathogenesis and treatment

Histologic bone changes of osteitis fibrosa and osteomalacia are commonly present in patients with end-stage renal disease. Although many patients are not symptomatic from these bone changes, some patients are severely disabled. Altered metabolism of vitamin D, calcium, phosphorus, and parathyroid hormone occurs in renal failure and contributes to the development of uremic bone disease. This article reviews the current theories of pathogenesis and treatment of renal osteodystrophy. In addition, the clinical presentation, pathogenesis, and treatment of the various aluminum-associated osteomalacic syndromes in uremia are discussed.

Interactions between aluminum and the actions and metabolism of vitamin D3 in the chick

The effects of intraperitoneal injections of aluminum chloride were tested on the intestinal calcium absorption and bone calcium mobilization responses to vitamin D3 and 1,25(OH)2D3, as measured by bioassay in chicks. Aluminum at 5 mg/kg given 5 days before the bioassay in vitamin D-deficient chicks, partially blocked the intestinal calcium absorption response to low (0.65 and 3.2 nmol), but not to higher (32 nmol) doses of vitamin D3. The responses to all doses (0.32-2.1 nmol) of 1,25(OH)2D3 were partially blocked by aluminum treatment. Serum calcium values were elevated in vitamin D-deficient chicks by aluminum administration, but no consistent effects of the treatment on bone calcium mobilization in response to vitamin D3 or 1,25(OH)2D3 were noted. Aluminum treatment in vivo led to decreased 25-OH-D3-1-hydroxylase activity subsequently measured in renal homogenates; under a variety of conditions, no direct effect of aluminum on 25-OH-D3 metabolism by primary cultures of chick kidney cells was observed. The results suggest that the ability of the intestine to respond normally to 1,25(OH)2D3 may be compromised by exposure to high levels of aluminum and that the effect of this element on 25-OH-D3 metabolism observed in vivo may not be exerted by direct action on the renal cell.

Secondary hyperparathyroidism in diabetic and nondiabetic patients on long-term continuous ambulatory peritoneal dialysis (CAPD)

Serum values of calcium, phosphate, alkaline phosphatases and parathyroid hormone (PTH) are reported for 24 diabetic and 26 nondiabetic patients treated with continuous ambulatory peritoneal dialysis (CAPD) for a total of 779 months, without the use of vitamin D or calcium supplements. Radiographic data are reported for 25 patients followed on CAPD for at least 12 months. Serum calcium was well maintained and control of hyperphosphataemia acceptable, but phosphate-binding therapy had to be continued in the majority of patients. Diabetic patients had lower serum phosphate levels and higher serum calcium than nondiabetic patients during the first year of CAPD. In nondiabetic patients the institution of CAPD was followed by a fall in PTH, possibly largely reflecting transperitoneal PTH elimination. No patient achieved normalization of serum PTH on CAPD. Although no symptomatic bone disease was observed, radiographic evidence of progressive hyperparathyroid bone disease developed in 3 of the 25 examined patients, all nondiabetic. In summary, long-term CAPD with a dialysate calcium concentration of 1.75 mmol/l seems to be compatible with normocalcaemia and a steady-state situation with regard to secondary hyperparathyroidism in the majority of patients. Despite transperitoneal elimination, serum PTH remains elevated, and definite progression of hyperparathyroidism is observed in some patients, however, probably making a case for vitamin D therapy and/or intraperitoneal or peroral calcium supplementation in these patients.

Serum concentration and peritoneal transfer of aluminum during treatment by continuous ambulatory peritoneal dialysis

The evolution of the aluminum (A1) serum levels during a 2-year follow-up and the peritoneal transfer of A1 were studied in 22 patients treated by continuous ambulatory peritoneal dialysis (CAPD), using a dialysate with a very low A1 concentration (r = 0.25 - 0.30 mumoles/liter). Patients were divided in three groups. A transfer of A1 from the patient to the dialysate was observed in all patients. In group 1, patients exclusively treated by CAPD and who have never received aluminum-containing phosphate binders (ACPB), mean level (+/- SD) of serum A1 stabilized within a safe range (0.60 +/- 0.28 mumoles/liter). In group 2 the oral administration of ACPB in patients exclusively treated by CAPD induced a slow and progressive increase of A1 serum concentration despite the increase of the A1 excretion through the peritoneal route. In group 3, patients previously treated by hemodialysis and receiving ACPB, the high serum A1 levels observed before treatment by CAPD decreased rapidly on CAPD. A1 removal through the peritoneum was higher in group 3 than in group 2 despite serum A1 levels not statistically different in both groups. A1 removal through the peritoneum is mainly influenced by serum and dialysate A1 concentration. A1 body stores could play a role in the transfer of A1 through the peritoneum. Three cases of A1 poisoning due to the accidental use of a dialysate with a high A1 content are reported.