Reversal of adynamic bone disease by lowering of dialysate calcium

Adynamic bone disease (ABD) is increasingly recognized, especially in dialysis patients treated with oral calcium carbonate, vitamin D supplements, or supraphysiological dialysate calcium. We undertook this study to assess the effect of lowering dialysate calcium on episodes of hypercalcemia, serum parathyroid hormone (PTH) levels as well as bone turnover. Fifty-one patients treated with peritoneal dialysis and biopsy-proven ABD were randomized to treatment with control calcium, 1.62 mM, or low calcium, 1.0 mM, dialysate calcium over a 16-month period. In the low dialysate calcium group, 14 patients completed the study. This group experienced a decrease in serum total and ionized calcium levels, and an 89% reduction in episodes of hypercalcemia, resulting in a 300% increase in serum PTH values, from 6.0+/-1.6 to 24.9+/-3.6 pM (P<0.0001). Bone formation rates, all initially suppressed, at 18.1+/-5.6 microm2/mm2/day rose to 159+/-59.4 microm2/mm2/day (P<0.05), into the normal range (>108 microm2/mm2/day). In the control group, nine patients completed the study. Their PTH levels did not increase significantly, from 7.3+/-1.6 to 9.4+/-1.5 pM and bone formation rates did not change significantly either, from 13.3+/-7.1 to 40.9+/-11.9 microm2/mm2/day. Lowering of peritoneal dialysate calcium reduced serum calcium levels and hypercalcemic episodes, which resulted in increased PTH levels and normalization of bone turnover in patients with ABD.

Bone density loss after allogeneic hematopoietic stem cell transplantation: a prospective study

The incidence and course of bone density abnormalities following hematopoietic stem cell transplantation are poorly understood and complicated by the impact of multiple factors. Hip, spine, and wrist bone mineral densities (BMDs) were measured in 104 adults (54 women, 54 men; mean age, 40 years [range, 18-64 years]) at 3 and 12 months after allogeneic transplantation. Clinical and laboratory variables were evaluated using univariate and multivariate analyses to determine risk factors for osteoporosis, fracture, and avascular necrosis. At 3 months posttransplantation, combined (male and female) hip, spine, and wrist z scores were -0.35, -0.42, and +0.04 standard deviations, respectively. At 12 months both men and women experienced significant loss of hip BMD (4.2%, P < .0001); changes in the spine and wrist were minimal. The cumulative dose and number of days of glucocorticoid therapy and the number of days of cyclosporine or tacrolimus therapy showed significant associations with loss of BMD; age, total body irradiation, diagnosis, and donor type did not. Nontraumatic fractures occurred in 10.6% of patients and avascular necrosis in 9.6% within 3 years posttransplantation. The decrease in height between pretransplantation and 12 months posttransplantation was significant (P = .0001). Results indicate that loss of BMD after allogeneic stem cell transplantation is common and accelerated by the length of immunosuppressive therapy and cumulative dose of glucocorticoid. An increased incidence of fracture and avascular necrosis may adversely impact long-term quality of life. Prevention of bone demineralization appears warranted after stem cell transplantation.

Vascular access survival and incidence of revisions: a comparison of prosthetic grafts, simple autogenous fistulas, and venous transposition fistulas from the United States Renal Data System Dialysis Morbidity and Mortality Study

OBJECTIVE

The study's aim was to evaluate access patency and incidence of revisions in patients initiating hemodialysis and to determine differences in access performance by type of access among patient subgroups.

METHODS

The study used data from the United States Renal Data System Dialysis Morbidity and Mortality Study Wave 2, which contained a random sample of dialysis patients initiating dialysis in 1996 and early 1997. Failures and revisions were evaluated among 2247 newly placed hemodialysis accesses by using Cox proportional hazards regression model and Poisson regression. Primary and secondary patency rates were estimated using the Kaplan-Meier method.

RESULTS

Fifteen hundred seventy-four prosthetic grafts, 492 simple autogenous fistulas, and 181 venous transposition fistulas were available for evaluation. Prosthetic grafts had a 41% greater risk of primary failure compared with simple fistulas (relative risk, 1.41; 95% CI, 1.22-1.64; P < .001) and a 91% higher incidence of revision (relative risk, 1.91; 95% CI, 1.60-2.28; P <.001). At 2 years, autogenous fistulas demonstrated superior primary patency (39.8% versus 24.6%, P < .001) and equivalent secondary patency (64.3% versus 59.5%, P = .24) compared with prosthetic grafts. When compared with simple fistulas, vein transpositions demonstrated equivalent secondary patency at 2 years (61.5% versus 64.3%, P = .43) but inferior primary patency (27.7% versus 39.8%, P = .008) and had a 32% increased incidence of revision (P = .04). Autogenous fistulas had superior primary patency compared with prosthetic grafts in all patient subgroups except for patients with previously failed access. Vein transpositions showed the greatest benefit in terms of patency and incidence of revision in women and in patients with previously failed access.

CONCLUSIONS

The preferential placement of autogenous fistulas may increase primary patency and decrease the incidence of revisions. Vein transpositions had similar secondary patency compared with simple fistulas, but required more revisions. The greatest benefit of a vein transposition fistula was seen in women and in patients with a history of access failure.

Assessment of a policy to reduce placement of prosthetic hemodialysis access

BACKGROUND

The aim of this study was to evaluate the determinants of access patency and revision, including the effects of reducing the placement of prosthetic hemodialysis access.

METHODS

A retrospective cohort study of all hemodialysis accesses placed at the Veteran's Administration Puget Sound Health Care System between 1992 and 1999 was conducted. A policy was instituted in 1996 that maximized the use of autogenous hemodialysis access. The impacts of the policy change, demographics, and comorbid factors on access type and patency, were examined. Primary and secondary patency rates were examined using the Kaplan--Meier method, and factors associated with failure and revision were examined using Cox proportional hazard models and Poisson regression.

RESULTS

During the study, 104 accesses (61 prosthetic grafts and 43 autogenous fistulas) were placed prior to 1996, and 118 (31 prosthetic grafts and 87 autogenous fistulas) were placed after 1996. There was a significant increase in autogenous fistulas placed after 1996 (87 out of 118) compared with before 1996 (43 out of 104, P < 0.001). At one year, autogenous fistulas demonstrated superior primary patency (56 vs. 36%, P = 0.001) and secondary patency (72 vs. 58%, P = 0.003) compared with prosthetic grafts. After adjustment for age, race, side of access placement, and history of prior access placement, patients with a prosthetic graft were estimated to experience a 78% increase in the risk of primary access failure when compared with similar patients having an autogenous access [adjusted relative risk (aRR) = 1.78, 95% CI 1.21--2.62, P = 0.003)]. Similarly, the adjusted relative risk of secondary access failure for comparing prosthetic grafts with autogenous fistulas was estimated to be 2.21 (95% CI 1.38--3.54, P = 0.001). The adjusted risk of access revision was 2.89-fold higher for prosthetic grafts than for autogenous fistulas (95% CI 1.88--4.44, P < 0.001).

CONCLUSIONS

Autogenous conduits demonstrated superior performance when compared with prosthetic grafts in terms of primary and secondary patency and number of revisions. A policy emphasizing the preferential placement of autogenous fistulas over prosthetic grafts may result in improved patency and a reduction in the number of procedures required to maintain dialysis access patency.

Risk factors for hip fracture among patients with end-stage renal disease

BACKGROUND

Although bone disease is well described among end-stage renal disease (ESRD) patients, little attention has been paid to the occurrence of fracture. We sought to identify factors that are associated with hip fracture among ESRD patients.

METHODS

Data from patients who participated in the United States Renal Data System Dialysis Morbidity and Mortality Study Wave 1 were used for this study. Hip fractures occurring among these patients between 1993 and 1996 were identified from Medicare claims data available from the United States Renal Data System. Cox proportional hazards models were used to estimate the risk of hip fracture associated with demographic and medical variables.

RESULTS

Of the 4952 patients included in this analysis, 103 sustained a hip fracture. In the multivariate analysis, age (per increasing decade, RR = 1.40, 95% CI 1.20, 1.64), female gender (RR = 2.26, 95% CI 1.48, 3.44), race (blacks compared with whites, RR = 0.58, 95% CI 0.37, 0.91), body mass index (per 1 unit increase, RR 0.89, 95% CI 0.86, 0.93), and the presence of peripheral vascular disease (RR 1.94, 95% CI 1.29, 2.92) were independently associated with hip fracture. Serum intact parathyroid hormone (iPTH), aluminum, diabetes, and bicarbonate levels did not appreciably influence the risk of hip fracture.

CONCLUSIONS

Demographic and other characteristics that predict risk of hip fracture in the population at large also do so in ESRD patients. However, we could identify no characteristics of ESRD or its treatment that were independently related to hip fracture incidence.

Anthropometric measures and risk of death in children with end-stage renal disease

We evaluated the association between anthropometric measurements and death among pediatric patients with end-stage renal disease (ESRD) using data from the Pediatric Growth and Development Special Study (PGDSS) from the US Renal Data System. Height, growth velocity, and body mass index (BMI) were used for the analysis of 1,949 patients in the PGDSS. To standardize these measurements, SD scores (SDSs) were calculated using population data from the Third National Health and Nutrition Examination Survey. Using Cox proportional hazards models, we assessed the association between anthropometric measures and death, controlling for demographic factors and stratifying by age. Multivariate analysis showed that each decrease by 1 SDS in height was associated with a 14% increase in risk for death (adjusted relative risk [aRR], 1.14; 95% confidence interval [CI], 1.02 to 1.27; P = 0.017). For each 1 SDS decrease in growth velocity among patients in our sample, the risk for death increased by 12% (aRR, 1.12; 95% CI, 1.00 to 1.25; P = 0.043). There was a statistically significant U-shaped association between BMI and death (P = 0.001), with relatively low and high BMIs associated with an increased risk for death. In children with ESRD, growth delay and extremes in BMI are associated with an increased risk for mortality.

Increased risk of hip fracture among patients with end-stage renal disease

BACKGROUND

Although patients with end-stage renal disease (ESRD) are at increased risk for bone loss, the risk of hip fracture in this population is not known. We compared the risk of hip fracture among dialysis patients with the general population.

METHODS

We used data from the United States Renal Data System (USRDS) to identify all new Caucasian dialysis patients who began dialysis between January 1, 1989, and December 31, 1996. All hip fractures occurring during this time period were ascertained. The observed number of hip fractures was compared with the expected number based on the experience of residents of Olmstead County (MN, USA). Standardized incidence ratios were calculated as the ratio between observed and expected. The risk attributable to ESRD was calculated as the difference between the observed and expected rate of hip fracture per 1000 person-years.

RESULTS

The number of dialysis patients was 326,464 (55.9% male and 44.1% female). There were 6542 hip fractures observed during the follow-up period of 643, 831 patient years. The overall incidence of hip fracture was 7.45 per 1000 person years for males and 13.63 per 1000 person years for females. The overall relative risk for hip fracture was 4.44 (95% CI, 4.16 to 4.75) for male dialysis patients and 4.40 (95% CI, 4.17 to 4.64) for female dialysis patients compared with people of the same sex in the general population. While the age-specific relative risk of hip fracture was highest in the youngest age groups, the added risks of fracture associated with dialysis rose steadily with increasing age. The relative risk of hip fracture increased as time since first dialysis increased.

CONCLUSIONS

The overall risk of hip fracture among Caucasian patients with ESRD is considerably higher than in the general population, independent of age and gender.

Symptomatic hypercalcemia of immobilization in a patient with end-stage renal disease

The phenomenon of hypercalcemia in immobilization is well known, but there is limited awareness of the potential for this complication in patients with end-stage renal disease (ESRD) on maintenance hemodialysis with reduced capacity for disposition of calcium. We describe such a patient who showed a calcemic response to just 3 days of immobilization in the setting of an acute illness marked by coma. Despite intensive initial therapy for hypercalcemia, including withdrawal of all calcium products and daily hemodialysis treatments using low calcium baths, her serum calcium rose to 14.0 mg/dL during the hospitalization; this metabolic abnormality appeared to perpetuate her stuporous state. Mobilization as an outpatient was the most effective therapy. Extensive testing was performed to rule out other causes for this patient's hypercalcemia. Greater recognition of acute hypercalcemia in patients with ESRD immobilized by various illnesses would preclude unnecessarily expensive and invasive testing for other causes of hypercalcemia.

Determinants of type and timing of initial permanent hemodialysis vascular access

BACKGROUND

We undertook a population-based study of hemodialysis (HD) patients to determine which factors are important in predicting the type of permanent access initially placed and if a functional permanent access is in place at the start of HD.

METHODS

Selected characteristics were abstracted from the United States Renal Data System (USRDS) Dialysis Morbidity and Mortality Study (DMMS) Wave 2. Logistic regression was used to estimate the independent contribution of specific characteristics in predicting whether the initial permanent access placed was an arteriovenous (AV) fistula compared with a polytetrafluoroethylene (PTFE) graft, and in predicting whether permanent access (fistula or graft) was in place at the initiation of dialysis.

RESULTS

Sixty-seven percent of the patients had an AV graft placed as their first permanent access. Characteristics important in predicting if a fistula was initially placed included age (per decade; aOR = 0.84, P < 0.001), female gender (aOR = 0.52, P < 0.001), body mass index (per standard deviation; aOR = 0.70, P = 0.09), avoiding blood draws (aOR = 1.96, P < 0.001), ability to ambulate (aOR = 2.24, P = 0.008), underlying renal disease (glomerular compared with diabetes, aOR = 2.19, P = 0.009), college education (aOR = 1.72, P = 0.002), and sharing in decision making (aOR = 1.50, P = 0.02). Thirty-four percent of patients (34.4%) had functional permanent access at the start of HD. Characteristics important in predicting which patients had functional permanent access included serum albumin (per 1 mg/dL increase, aOR =1.55, P = 0.003), erythropoietin prior to starting HD (aOR = 1.79, P = 0.002), fewer predialysis nephrologist visits (aOR = 0.21, P < 0.001), and when the patient was told they had renal disease (aOR = 0.33, P = 0.002).

CONCLUSIONS

PTFE grafts were the most common initial permanent access. The majority of patients did not have permanent access at the start of dialysis. Factors that are thought to compromise identification of adequate veins were important predictors of PTFE graft placement. Permanent access at the start of HD was largely a function of early patient education and early referral to a nephrologist.

Screening plasma aluminum levels in relation to aluminum bone disease among asymptomatic dialysis patients

Aluminum accumulation in plasma and tissues is a well-described complication among persons undergoing peritoneal dialysis or hemodialysis. Excess bone aluminum is associated with low bone formation rates and increased risk for fractures. Current recommendations for care of patients with end-stage renal disease include screening for aluminum toxicity with plasma aluminum levels; patients with levels below 40 microg/L are considered to be at low risk for aluminum bone disease (ABD). We examined data from the Toronto Renal Osteodystrophy Study to evaluate the performance of plasma aluminum levels in screening for ABD. Two hundred fifty-eight unselected patients undergoing peritoneal dialysis (n = 143) or hemodialysis (n = 115) underwent diagnostic bone biopsy and measurement of plasma aluminum level. Sixty-nine patients (26.7%) were identified as having ABD, defined as low or normal bone formation rates with 25% or more bone surface aluminum staining. Plasma aluminum level was strongly associated with the presence of ABD; the odds ratio was 1.4 for each increase of 10 microg/L (95%CI, 1.2, 1.6). However, only 50.1% of patients with a plasma aluminum level of 40 microg/L or greater had ABD, whereas 14.2% of patients with a level below this threshold also had ABD. Using this cutoff level of 40 microg/L, the sensitivity and specificity were 65.2% and 76.7%, respectively. We conclude that although there is a correlation between high aluminum levels and ABD, a patient's plasma aluminum level does not predict well the presence of ABD in spite of a relatively high prevalence of disease.

Renal osteodystrophy in pre-dialysis patients: ethnic difference?

The purpose of the present study is to investigate whether an ethnic difference exists in the incidence of renal osteodystrophy between Asian and Western countries in end-stage renal disease (ESRD) patients. We evaluated bone histology in 58 pre-dialysis patients (28 male, 30 female; mean age: 47.7 years). All patients had bone biopsies with quantitative histomorphometry and serological parameters such as intact PTH, osteocalcin, total alkaline phosphatase, and basal and deferoxamine-stimulated serum aluminum levels. We observed that 91.4% of all evaluated patients showed renal osteodystrophy before the start of dialytic therapy. Mild osteitis fibrosa were observed in 21 patients (36.2%), severe osteitis fibrosa in 5 patients (8.6%), mixed lesions in 7 patients (12.1%), osteomalacia in 6 patients (10.3%), aplastic bone disease in 14 patients (24.1%), and normal bone in 5 patients (8.6%). Among the bone histomorphometric parameters, fibrosis area rate (%) showed the best correlation with intact PTH, and osteocalcin and osteoid area rate (%) with total alkaline phosphatase. Aluminum-related bone disease was not observed. Among patients with aplastic bone disease, only 14.3% showed aluminum deposition of any significance (5% < stainable bone surface aluminum < 25%). In the diabetic patients, aplastic bone disease was most common, but no case was related to aluminum intoxication. In conclusion, the distribution of renal osteodystrophy in our study was different from that of Western countries in pre-dialysis patients. Our patients tended to have more mild-form osteitis fibrosa and normal findings, and less severe-form osteitis fibrosa and aplastic bone disease. Aluminum-related bone disease was not observed.

A calcimimetic agent acutely suppresses parathyroid hormone levels in patients with chronic renal failure. Rapid communication

The control of hyperparathyroidism in patients with chronic renal failure continues to be a problem, particularly when parathyroid hormone (PTH) suppression becomes refractory to calcitriol activation of parathyroid cell 1,25-dihydroxyvitamin D receptors. To evaluate whether parathyroid cell calcium receptor activation may be useful in suppressing PTH levels, we tested the safety and effectiveness of a novel calcimimetic agent in dialysis patients with hyperparathyroidism. In a prospective, dose finding study, the calcimimetic agent, NPS R-568, was administered orally to seven patients at the start of a hemodialysis session and again 24 hours later. Plasma PTH, calcitonin and ionized calcium levels were measured over a 48 hour period and patients were observed for adverse events. Plasma PTH levels fell abruptly in all patients after a single dose of the compound, with the maximum suppression occurring within one to two hours after its administration. Following the administration of low doses (40 or 80 mg), the suppressed PTH levels rose to baseline values over 48 hours, whereas in patients who received high doses (120 or 200 mg) the mean PTH level remained 51% below baseline. Plasma calcitonin increased after the administration of both low and high doses (peak effect within 4 to 6 hr), with levels always returning to baseline by 48 hours. There were no episodes of hypocalcemia and no adverse effects were reported. We conclude that the activation of parathyroid cell calcium receptors by a novel calcimimetic compound is safe and effective in acutely suppressing PTH secretion in dialysis patients with hyperparathyroidism. Whether concomitant stimulation of calcitonin secretion will provide added beneficial effects on bone remodeling remains to be determined in long-term studies.

Avascular necrosis following bone marrow transplantation: a case-control study

The role of specific immunosuppressive agents in the development of avascular necrosis (AVN) following hematopoietic stem cell and solid organ transplantation remains unclear. To further explore this question, we conducted a case-control study of patients who underwent bone marrow transplantation (BMT) at the Fred Hutchinson Cancer Research Center. 96 of 1939 long-term survivors transplanted between May 1976 and October 1993 were identified as having AVN. Eight patients were excluded because AVN developed before transplant and one was excluded due to restrictions on reviewing follow-up records. The remaining 87 patients developed AVN a mean of 26.3 +/- 2 months posttransplant and were matched for age, gender, and date of transplant to other BMT recipients. Records were reviewed for corticosteroid and cyclosporine use, pretransplant conditioning with total body irradiation (TBI), and other information including disease for which the transplant was indicated, type of transplant, the occurrence of acute and chronic graft-vs.-host disease, and steroid use prior to transplant. Adjusted odds ratios (ORs) were obtained from conditional logistic regression for 87 matched pairs. Posttransplant steroid use was a risk factor for the occurrence of AVN (adjusted OR, 14.4; 95% CI, 2.8-73.2), with the greatest risk associated with those receiving steroids at the time of diagnosis of AVN (adjusted OR, 31.9; 95% CI, 4.4-248.9). There was no further increasing risk associated with increasing duration of steroid use. Conditioning with TBI was also associated with the occurrence of AVN (adjusted OR, 3.2; 95% CI, 1.1-9.7); however, cyclosporine was not a risk factor for AVN (adjusted OR, 0.5; 95% CI, 0.1-1.9). Our results support the hypothesis that AVN following BMT has a strong association with the administration of corticosteroids. TBI may be an additional risk factor, and cyclosporine does not appear to contribute to an increased incidence of AVN.

Evidence that serum phosphate is independently associated with serum PTH in patients with chronic renal failure

There has been controversy regarding the initial pathogenic events involved with the hyperparathyroidism of chronic renal failure (CRF). Low serum levels of 1,25-dihydroxyvitamin D in uremic patients are postulated by some as having a role in permitting higher parathyroid hormone (PTH) secretion. However, recent animal and in vitro studies strongly suggest that phosphate has a direct effect on parathyroid cells to enhance PTH secretion. To evaluate the relationships among serum phosphate, calcium, PTH, and 1,25-dihydroxyvitamin D in uremic humans, we performed a cross-sectional analysis of 84 patients with varying levels of CRF. Using stepwise regression analysis after adjusting for multiple comparisons, we found that serum phosphate correlated directly with serum PTH (r = 0.62, P < 0.01) in patients with mild to moderate CRF (creatinine < or = 3.0 mg/dL), independent of serum calcium and 1,25-dihydroxyvitamin D levels. In patients with more severe renal failure (creatinine > 3.0 mg/dL), only the serum calcium correlated with serum PTH (r = -0.47, P < 0.01). While serum 1 ,25-dihydroxyvitamin D showed no correlations with PTH, phosphate, or calcium at any stage of renal failure, the mean 1,25-dihydroxyvitamin D level in patients with mild CRF was lower than that in age-matched controls (24 +/- 3 pg/mL v 37 +/- 2 pg/mL; P < 0.01), suggesting that low 1,25-dihydroxyvitamin D was permissive for enhanced PTH secretion. These data demonstrate an independent association of serum phosphate with PTH in patients with CRF and suggest that phosphate may directly enhance PTH secretion in this setting. This study supports recent animal studies showing a direct parathyroid cell effect of phosphate on PTH secretion.

Dimensional accuracy of improved dental stone and epoxy resin die materials. Part II: Complete arch form

STATEMENT OF PROBLEM

Little information has been reported with regard to the dimensional accuracy of improved dental stone materials for reproduction of an entire arch form.

PURPOSE

The purpose of this study was to evaluate the ability of an epoxy resin die material and a type IV dental stone to dimensionally reproduce an entire arch form.

MATERIAL AND METHODS

Models were fabricated and measurements were made of reference marks to calculate dimensions from first molar to the midline bilaterally and between first molars. Each measurement was repeated three times and the mean measurement and percent relative change was calculated for each dimension.

RESULTS

The results revealed that the difference in the relative change in two dimensions was statistically significant for the epoxy resin group (p < 0.05).

CONCLUSIONS

The materials provided a similar degree of dimensional accuracy in reproducing a complete arch when used with addition silicone impression material.

Dimensional accuracy of improved dental stone and epoxy resin die materials. Part I: Single die

STATEMENT OF PROBLEM

Improved dental stone has been widely used for producing dies for the fabrication of restorations with the lost-wax technique. Improved dental stone is used for several reasons, but it is selected most often because of its reasonable cost, ease of use, and ability to produce consistent results.

PURPOSE

This study evaluated the ability of an epoxy resin die material and a type IV dental stone to dimensionally reproduce a custom-fabricated metal die.

MATERIAL AND METHODS

Dies were fabricated and measurements were made from three reference lines. Measurements were repeated three times for the master die and for the specimen dies. A mean measurement and percent relative change for each dimension was calculated.

RESULTS

A significant difference in the relative change for die height was found between the groups studied (p < 0.003).

CONCLUSIONS

This epoxy die system will provide a degree of dimensional accuracy comparable to gypsum when used with addition silicone impression material.

Vasectomy is associated with an increased risk for urolithiasis

We evaluated vasectomy as a potential risk factor for urolithiasis. Vasectomy is a common method of contraception among otherwise healthy men. This is also the population at highest risk for urolithiasis. We conducted a case-control study of patients in a large prepaid health maintenance organization. Cases were men experiencing initial episodes of urolithiasis, ascertained by reviewing radiology logs and medical records. The age-matched controls were men with no history of urolithiasis. In logistic regression models, the relative risk of urolithiasis for men with vasectomies compared with men without vasectomies was 1.9 for men younger than 46 years of age (95% confidence interval = 1.2 to 3.1, P = 0.005), and the relative risk was 0.9 (95% confidence interval = 0.5 to 1.5, P > 0.8) for men who were at least 46 years old. The relative risk of urinary calculi was 2.0 (95% confidence interval 1.0 to 4.1, P < 0.05) for men with vasectomies 0 to 4 years before evaluation compared with men without vasectomies, and the excess risk persisted as long as 14 years postvasectomy. Vasectomy was associated with a twofold increased risk for urolithiasis in men younger than 46 years of age. This increased risk may persist for up to 14 years postvasectomy. Given the large number of men who undergo vasectomy worldwide each year, the increased risk for urolithiasis among vasectomized men may result in substantial excess morbidity.

Burn-associated bone disease in sheep: roles of immobilization and endogenous corticosteroids

To determine the role of immobilization in the pathogenesis of burn-associated bone disease, we selected the sheep as a model to study the effects of burn injury compared with a sham-burned control group. Seven of the sheep were subjected to controlled 40% flame burn, and seven underwent anesthesia with arterial and venous cannulation but without burn. After labeling newly formed bone with tetracycline and calcein, the sheep were killed 2 weeks after burn or sham burn, and the iliac crest and lumbar vertebrae were analyzed for histomorphometry. Analysis failed to demonstrate a significant reduction of bone formation rate in the burned sheep. Osteoid area and surface and osteoblast surface, which correlated significantly with bone formation rate (r = 0.49, p < 0.025), were reduced in the burned sheep. Results suggest that immobilization may play a primary role in the pathogenesis of burn-associated bone disease, but the presence of differences in other histomorphometric features indicates the bone disease is multifactorial.

Dietary and behavioral risk factors for urolithiasis: potential implications for prevention

Few studies have examined urolithiasis in primary care populations, and limited data are available on non-drug interventions to reduce the risk for urinary calculi. Therefore, we conducted a case control study of patients enrolled in a large prepaid health maintenance organization. The 240 study cases were men experiencing initial episodes of urolithiasis, ascertained by reviewing radiology procedure logs and medical records. The 392 controls were age-matched men with no history of urolithiasis chosen from a list of randomly selected men. Data were collected using standardized telephone interviews. Odds ratios were calculated for potential risk factors. In logistic regression analyses the risk for urinary tract calculi was related to both consumption variables, such as a low-fat or weight reduction diet (adjusted odds ratio, 0.41; P < 0.0005) and beer drinking (adjusted odds ratio, 0.41; P < 0.0001), and to demographic variables, such as African-American ethnicity (adjusted odds ratio, 0.29; P = 0.03) and a positive family history (adjusted odds ratio, 2.22; P < 0.001). These findings suggest the need to evaluate appropriate behavioral interventions to reduce the morbidity associated with urolithiasis. Prospective studies should evaluate the possibilities that beer drinking, even in modest amounts, and a low-fat or weight reduction diet are associated with substantial reductions in risk.

Interactions between dietary calcium and caffeine consumption on calcium metabolism in hypertensive humans

Abnormal calcium metabolism has been implicated in human hypertension. Caffeine consumption may contribute to hypertension since it increases urinary calcium excretion. Nineteen hypertensive subjects (HTN) and nineteen age and gender matched normotensive controls (NTC) who habitually consumed at least 175 mg caffeine daily were studied before and after abstinence from all caffeine (CAF) consumption for 2 weeks. Caffeine abstinence (CAF-) increased fasting serum ultrafiltrable calcium in HTN and NTC, but not serum total calcium. Parathyroid hormone (PTH) levels decreased after CAF abstinence in 14 of 18 HTN subjects, including all seven subjects consuming less than 700 mg calcium daily. Three day dietary calcium intakes and 72 h urinary excretion of calcium were not different between CAF+ and CAF- or between HTN and NTC. A morning caffeine dose of 6 mg/kg lean body mass increased urinary Ca/creatinine ratios similarly for 2 h after beverage consumption in both HTN and NTC. Caffeine consumption stresses calcium metabolism in hypertensive individuals, especially those consuming less than 700 mg calcium daily.

The aplastic form of renal osteodystrophy

That bone disease accompanies renal failure has been known for over 100 years. This bone disease (renal osteodystrophy) has been variously attributed to hyperparathyroidism, vitamin D deficiency, aluminium toxicity, iron toxicity, uraemia, and a host of other aetiologies. In addition, the form the bone disease takes has been variously described as osteitis fibrosa, osteomalacia, mixed uraemic osteodystrophy and the aplastic (adynamic) lesion. In this manuscript we will focus on the aetiology, consequences, diagnosis and possible management of the aplastic form of the disease. The renal osteodystrophy study was a prospective, cross-sectional study of renal bone disease in a largely unselected population of patients receiving dialysis in three hospitals in Toronto. A variety of non-invasive data (parathyroid hormone (PTH), aluminium, etc.) and bone histology were obtained and analysed to assess pathogenesis, diagnostic criteria and management. We have defined the aplastic lesion as having low bone formation without a marked increase in unmineralized osteoid (i.e. excluding osteomalacia). We have noted that it may be associated with increased aluminium or little to no aluminium. With increased aluminium the patients have a poorer prognosis both with regards to bone disease and mortality, and they should be managed appropriately to alleviate aluminium toxicity. With lesser amounts of aluminium, morbidity and mortality are less severely impacted, but not normal. We have shown that the low bone formation, of the aplastic lesion without aluminium may be "normalized' by increasing PTH levels. It is concluded that aplastic bone disease carries adverse consequences both in terms of bone problems and survival. In the absence of aluminium toxicity the stimulation of PTH effectively corrects the bone formation abnormality. Whether this will alleviate the adverse consequences will be difficult to study. Avoiding the problem by not over-suppressing PTH seems a reasonable approach at this point.

Relationship between intact 1-84 parathyroid hormone and bone histomorphometric parameters in dialysis patients without aluminum toxicity

With the markedly reduced usage of aluminum salts in renal failure, parathyroid hormone (PTH) has become the major determinant of currently seen bone disease. Clinicians now must consider what PTH level should be sought. Too low a level may lead to the aplastic bone lesion (low turnover bone), and too high a level may cause osteitis fibrosa. Furthermore, conventional normal PTH levels may not be a suitable target because of the well-known resistance to PTH in uremic patients. In this report, we derive the PTH levels that best distinguish patients with low and high bone formation states from those with normal bone formation in a group of 175 dialysis patients without aluminum toxicity. Using bone histological parameters, we propose that ideally PTH levels should be maintained between 10 pmol/L (100 pg/mL) and 20 to 30 pmol/L (200 to 300 pg/mL) in chronic dialysis patients, levels two to four times the upper limit of values found in normal subjects.

Aplastic bone: a nondisease of medical progress

Aplastic bone is characterized by a low bone formation rate, usually with no other histological abnormalities. Initially, it was thought to be caused by aluminum and was associated with a substantial morbidity. In the current milieu of dialysis, it is usually (> 2/3 of the time) not a result of aluminum toxicity. In the absence of large amounts of aluminum, aplastic bone is not an important cause of bone symptoms. It generally can be diagnosed by noninvasive means. Longer duration follow-up of such patients is needed, but up to now there is no evidence that this condition is a disease needing therapy.

Interactions between dietary caffeine and calcium on calcium and bone metabolism in older women

OBJECTIVE

Our purpose was to determine the effect of 2 weeks of caffeine abstinence on calcium (Ca) and bone metabolism in women habitually consuming caffeine and either low or moderate amounts of Ca.

METHODS

Participants were 25 women, aged 39-76 years (mean 65 years, median 57 years) habitually consuming at least 200 mg caffeine daily. Three days of dietary records and 24-hour urine collections were made immediately prior to collection of fasting blood and 1-hour urine in a metabolic unit. Women were classified as low Ca consumers (414-584 mg daily) or moderate Ca consumers (662-1357 mg daily) based on 6 days of diet records.

RESULTS

Women in the low Ca group had higher levels of serum ultrafiltrable Ca (UFCa) after caffeine abstinence (1.40 mmol/L CAF+ vs 1.52 mmol/L CAF-, p < 0.01), while there were no differences between experimental periods for UFCa in the moderate Ca group (1.35 mmol/L CAF+ vs 1.38 mmol/L CAF-, ns). Women in the low Ca group also had lower serum bone isoenzyme alkaline phosphatase levels after caffeine abstinence (9.3 U/L CAF+ vs 8.8 U/L CAF-, p < 0.05), while no significant changes were seen in bone alkaline phosphatase in the moderate Ca consumers (8.7 U/L CAF+ vs 8.9 U/L CAF-, ns). Fasting total serum Ca, urinary hydroxyproline/creatinine, and Ca/creatinine ratios were unchanged in both dietary groups. Three-day mean 24-hour urinary Ca excretion decreased after caffeine abstinence in the moderate Ca group only. There were no differences in dietary intakes of Ca from dairy products between CAF+ and CAF- in either the low or moderate Ca groups.

CONCLUSION

Abstinence from moderate caffeine intake (mean 5.8 mg/kg lean body mass, 383 mg/day caffeine) raises ultrafiltrable Ca and decreases bone alkaline phosphatase in older women consuming < 600 mg Ca daily.

Post-and-core assemblies made with an accelerated pattern elimination technique

PURPOSE

Accelerated pattern elimination has the potential for increasing productivity. This study evaluated the accelerated pattern elimination technique using three commonly used phosphate-bonded investments.

MATERIALS AND METHODS

Part one of this study determined the mean time interval from start of mixing to the maximum exothermic setting reaction temperature for each investment. A chromel/alumel thermocouple was placed at the heat center of a methylcellulose lined casting ring, using wet or dry ring liner. Investments were vacuum mixed at the recommended ratio for the accelerated technique. Colloidal silica solution and ddH2O were combined at a 50:50 ratio to meet the manufacturer's recommended liquid volume. Part two determined the dimensional reproduction of a standardized pattern and its casting using both casting techniques. Mixing ratios were the same as in part one for the accelerated technique and 75% colloidal silica to 25% double-distilled water (ddH2O) for the conventional technique. The accelerated technique used the mean setting time established in part one followed by a 15-minute furnace holding time at 725 degrees C (1350 degrees F). The conventional technique used a 1-hour bench setting time, followed by placing the mold into a cold furnace. A controlled rate of climb to a maximum temperature of 725 degrees C (1350 degrees F) was used with a 1-hour soak time. Each pattern and its casting were measured at four sites: (1) Length of the post-and-core assembly, (2) maximum core diameter, (3) post diameter at the core base, and (4) post diameter at its apex.

RESULTS

A significant difference was found between the time interval to maximum exothermic setting reaction temperature for all the investments (P < .01). The accelerated technique produced castings with a relative dimensional increase of 0.11% to 4.80%. The conventional technique ranged from a 0.04% decrease in size to an increase of 3.65%. Castings made with the accelerated technique were significantly different than those made with the conventional technique (P < .01).

CONCLUSIONS

Differences in the time interval to maximum exothermic setting reaction temperature indicate that each phosphate investment should have a recommended setting time before introduction into the furnace. The carbon-containing investment showed the least relative change of the three investments evaluated for both casting techniques.

Aplastic osteodystrophy without aluminum: the role of "suppressed" parathyroid function

We evaluated 259 dialysis patients using serum parathyroid hormone (PTH, IRMA; normal range 1 to 5.5 pM or 10 to 55 pg/ml), the deferoxamine infusion test and iliac crest bone biopsy to determine the various forms of renal osteodystrophy and their risk factors. Although half of the biopsied patients had low turnover osteodystrophy, evidence of aluminum toxicity was present in only 1/3 of them. Additional risk factors for this bone lesion included treatment with peritoneal dialysis, ingestion of calcium carbonate, diabetes mellitus and advanced age. The PTH levels in patients with the aplastic lesion were significantly lower than in patients with normal or high bone turnover lesions [7.7 +/- 6.1 vs. 36.9 +/- 3.2 pM (77 +/- 61 vs. 369 +/- 32 pg/ml), P < 0.0001]. Aside from hypercalcemia, these patients were relatively asymptomatic. In a second study, 10 patients on peritoneal dialysis with the aplastic lesion had their dialysate calcium lowered from 1.62 to 1.0 mM. This resulted in a significant increase in PTH levels, from [3.7 +/- 0.8 to 10.6 +/- 1.9 pM (37 +/- 8 to 106 +/- 19 pg/ml), P < 0.001] which persisted over the nine-month observation period. In conclusion, the aplastic lesion is the most common form of renal osteodystrophy, with aluminum intoxication implicated in only 1/3 of the cases. In the remainder, factors identified include therapy with peritoneal dialysis using supraphysiological dialysate calcium, oral CaCO3 intake and diabetes mellitus.(ABSTRACT TRUNCATED AT 250 WORDS)

Metabolic bone disease in adults receiving long-term parenteral nutrition: longitudinal study with regional densitometry and bone biopsy

A syndrome of bone pain and fractures has been described in patients receiving long-term support from parenteral nutrition containing large quantities of aluminium or vitamin D2. Whether this same syndrome occurs in patients supported by current therapeutic regimens is controversial. In this study, bone health was longitudinally evaluated over 7 to 61 months in 14 subjects maintained on long-term parenteral nutrition. The parameters of bone health evaluated included bone mass as measured by single and dual photon absorptiometry and quantitative histomorphometry of bone biopsies. There was a striking heterogeneity in baseline measures of bone health. Mean bone density of parenteral nutrition patients was significantly below expected values on entry into the study at both the distal radius (z score = -0.76 +/- 0.27) and the lumbar spine (z score = -1.17 +/- 0.27). Mean areal density at the forearm was less severely depressed (z score = -0.62 +/- 0.34). The longitudinal changes in bone density and morphology were heterogeneous, with some subjects showing deterioration, others improvement, and still others no change. We conclude that patients already established on parenteral nutrition frequently have osteopenia. The group as a whole did not demonstrate normalization of the osteopenia, but our results also suggest that current parenteral nutrition formulations low in aluminum and vitamin D2 do not necessarily cause worsening of bone health. The etiology of this clinical syndrome merits additional study.

Bone disease in burn patients

Burn patients are at risk for bone disease due to aluminum (Al) exposure from use of antacids and albumin, partial immobilization, and increased production of endogenous glucocorticoids. Moreover, severely burned children are growth impaired up to 3 years after the burn. To determine the extent of bone disease, we studied nine men and three women, ages 18-41 years, with greater than 50% body surface area burn. Seven patients underwent iliac crest bone biopsy following double tetracycline labeling, one additional patient expired after a single label, and three others had postmortem specimens obtained for quantitative Al only. Serial serum and urine samples were obtained weekly until biopsy or death. All biopsied patients had reduced bone formation and osteoid area, surface, and width, with mineral apposition rate, osteoblast surface, and osteoclast number with normal eroded surfaces compared to age- and sex-matched normal ambulatory volunteers. Burn patients also had reduced bone formation, mineral apposition rate, osteoid area, and surface compared to age-matched volunteers at short-term bed rest. Serum levels of osteocalcin were low. Most patients had mild hypercalcemia but only a third had hypercalciuria. All patients had elevated Al in blood or urine; urine Al correlated inversely with serum osteocalcin. In 60% significant bone Al was detectable by stain or quantitation. Our data are compatible with burn patients having markedly reduced bone turnover. Al loading, partial immobilization, endogenous corticosteroids, and cytokine production may be among the etiologic factors.

The spectrum of bone disease in end-stage renal failure--an evolving disorder

We have assessed the bone histology in 259 chronic dialysis patients, all of whom were in the same dialysis program. All patients had bone biopsies with quantitative histomorphometry, intact parathyroid hormone (PTH) measurements, basal and deferoxamine stimulated serum aluminum levels. Results demonstrate the increased incidence of the recently described aplastic bone lesion, particularly in patients treated with peritoneal dialysis (PD). Aluminum-related bone disease is much less common than previously described, perhaps in relation to the declining use of aluminum as a phosphate binder. A different pattern of bone lesions is seen in PD as compared with hemodialysis (HD), with low turnover disorders comprising 66% of the lesions seen in PD and high turnover lesions accounting for 62% of the bone histologic findings in HD. The difference in these patterns may relate to alterations in PTH levels, as mean PTH levels in HD patients were 2-1/2 times the levels found in PD patients (P < 0.0005), while older age, higher prevalence of diabetes and a shorter duration of dialysis may also have contributed to the findings in the PD patients. We suggest that PD, perhaps by maintaining calcium at higher levels, may more effectively suppress the parathyroid gland.

Effects of 1-week head-down tilt bed rest on bone formation and the calcium endocrine system

To understand the potential early responses of human bone and the calcium endocrine system to spaceflight, we studied 8 healthy men, aged 35-44 years before, during, and after bed rest in a -6 degrees head-down tilt model for microgravity. Based on a novel single-dose labeling schedule, average rates of bone formation in the iliac crest were reduced in 6, unchanged in 1, and increased in 1 following the bed rest period. The decrease was greatest for subjects whose daily walking miles were highest (r = -0.762, p less than 0.05, n = 7). Before a measurable increase in ionized serum calcium the sixth bed rest day, there was increased excretion of urinary calcium and sodium, evident the first 2 bed-rest days and parallel for the entire week (r = 0.92, p less than 0.001). Reduced excretion of phosphorus and 3', 5' cyclic adenosine monophosphate on the first and second bed rest days was followed by an increase in serum phosphorus by the sixth bed rest day. Depressed serum concentrations of parathyroid hormone and 1,25-dihydroxyvitamin D were manifest by the sixth and seventh bed rest days. The similarity of the response of bone and the calcium endocrine system of healthy men after only 7 days to results of longer term bed rest studies emphasizes the responsiveness of the adult human skeleton to biomechanical stimuli induced by changes in activity and/or position.

Beta 2-microglobulin deposition in bone in chronic renal failure

Recently, there have been reports of beta 2-microglobulin (beta 2 m) related amyloid deposition in perineural and periarticular tissues in patients receiving long-term hemodialysis, but it has been rarely described in bone. We, therefore, examined previously obtained bone biopsy specimens in patients receiving long-term hemodialysis to determine the prevalence of beta 2 m deposition in bone and to assess the relationship between beta 2 m deposits and bone histomorphometry. We found beta 2 m deposits in bone in 8% of 224 patients examined. Bone deposition of beta 2 m was absent in patients who were on dialysis for less than six years, but was present in 19% who dialyzed longer than 10 years. beta 2 m deposits were found in specimens from the iliac crest, femoral bone, tibia, vertebra and rib. In the iliac crest beta 2 m deposition was localized predominantly to the periosteum. Among these patients with beta 2 m in iliac crest periosteum, 62% had suffered a femoral neck fracture compared to only 4% of matched patients who had negative staining for beta 2 m in the iliac crest (P less than 0.001). Histologically, osteitis fibrosa seemed more common in patients positive for beta 2m than in patients negative for beta 2m deposition. We conclude that beta 2m deposition in bone is common in uremic patients who have received hemodialysis longer than 10 years. The high prevalence of femoral neck fracture in patients with beta 2m localized to the periosteum of the iliac crest suggests that this involvement may be useful to predict susceptibility to femoral fracture.

Periarticular tumoral calcinosis and hypercalcemia in a hemodialysis patient without hyperparathyroidism: a case report

We present a case of a 58-yr-old male to illustrate the scintigraphic, roentgenographic, clinical, and pathologic features of periarticular tumoral calcinosis that occurred in a hemodialysis patient. Soft-tissue calcifications developed 3 yr after onset of hemodialysis, became progressively larger during the ensuing five years, and culminated in voluntary withdrawal from dialysis because of the extreme discomfort and lack of mobility that resulted from the calcinosis. Histologically, an aplastic disorder was present with very low bone formation. On bone scintigraphy, intense calcium uptake in soft tissues implied that it was metabolically active. We hypothesize that this high metabolic activity contributed to the persistent hypercalcemia observed during the patient's last year of life.

Osteonecrosis in patients receiving dialysis: report of two cases and review of the literature

Two patients receiving maintenance dialysis therapy developed osteonecrosis, the first in the humeral head and the second in the talus. Both patients lacked known risk factors for developing osteonecrosis. A possible pathogenic role of secondary hyperparathyroidism in this disorder is suggested. Rheumatologists evaluating patients receiving maintenance dialysis with rheumatic manifestations should be aware of this potential complication.

Effects of dietary caffeine on renal handling of minerals in adult women

Thirty-seven women, aged 31-78 years, on two separate mornings consumed a decaffeinated beverage to which 6 mg caffeine/kg lean body mass or no caffeine were added. Total urine output of water, calcium, magnesium, sodium, chloride, potassium and creatinine increased in the two hours following caffeine ingestion when compared to the control beverage. Increased urinary mineral (mg)/urinary creatinine (g) ratios were seen for calcium (120 to 200), magnesium (70 to 110), sodium (3,800 to 6,200) and chloride (9,200 to 14,800), following the caffeinated beverage. Creatinine clearance did not change significantly. The percent reabsorption of calcium (98.6% to 97.5%, p less than .001) and magnesium (97.0% to 94.2%, p less than .0001) decreased significantly during the post-caffeine period. The calcium and magnesium filtered loads did not differ significantly between the caffeine and no caffeine beverages. Therefore, caffeine-induced urinary loss of calcium and magnesium is largely attributable to a reduction in calcium and magnesium renal reabsorption, although the physiological mechanism and tubular segment affected remain to be established.

Intravenous calcitriol in the treatment of refractory osteitis fibrosa of chronic renal failure

Osteitis fibrosa, a frequent complication of chronic renal failure, is characterized by increased rates of bone formation and bone resorption due to increased secretion of parathyroid hormone (PTH). Effective treatment with oral calcitriol is often impossible in patients with osteitis fibrosa, because low doses may cause hypercalcemia. Because short-term infusions of intravenous calcitriol are capable of suppressing the secretion of parathyroid hormone in patients with uremia without causing hypercalcemia, we evaluated the effectiveness of long-term intermittent calcitriol infusions (1.0 to 2.5 micrograms three times weekly, during dialysis) in treating severe osteitis fibrosa in 12 consecutive patients on hemodialysis whose disease was refractory to conventional therapy. After a mean (+/- SE) treatment period of 11.5 +/- 1.4 months, the mean bone-formation rate declined from 1642 +/- 277 to 676 +/- 106 microns 2 per square millimeter per day (P less than 0.01) in the 11 patients who successfully completed the study. Similar reductions occurred in the osteoblastic osteoid (18 +/- 3 to 9 +/- 2 percent; P less than 0.01) and the degree of marrow fibrosis (6.2 +/- 1.7 to 3.5 +/- 1.3 percent; P = 0.01). Concomitant serum biochemical changes included increased calcium levels (2.55 +/- 0.03 to 2.67 +/- 0.05 mmol per liter; P less than 0.01), decreased alkaline phosphatase levels (489 +/- 77 to 184 +/- 32 U per liter; P less than 0.001), and decreased levels of PTH (amino-terminal, 172 +/- 34 to 69 +/- 16 ng per liter in five patients, P less than 0.03; and carboxy-terminal, 1468 +/- 467 to 1083 +/- 402 ml-eq per liter in six patients, P not significant). Although the majority of the patients had transient episodes of asymptomatic hypercalcemia, this complication could be quickly reversed by temporarily halting treatment or decreasing the dose of calcitriol. We conclude that long-term intermittent infusions of intravenous calcitriol are effective in ameliorating osteitis fibrosa in patients on dialysis. Patients whose osteitis fibrosa is refractory to oral calcitriol and who are candidates for parathyroidectomy should be considered first for intravenous calcitriol therapy.

Single-dose tetracycline labeling for bone histomorphometry

A single oral dose of tetracycline deposits in bone and is readily identified with fluorescence microscopy. Two such time-spaced labels can be used to determine bone dynamic features. This is as accurate as conventional three-day labeling periods. The simplicity, improved compliance, and substantial reduction in time it takes to prepare a patient for bone biopsy all appear to be advantageous when compared with current recommendations.

Metabolic bone disease of total parenteral nutrition: course after changing from casein to amino acids in parenteral solutions with reduced aluminum content

Bone disease with total parenteral nutrition (TPN) has been attributed to aluminum loading or vitamin D therapy. We studied 17 patients who first received TPN containing casein hydrolysate with high Al and ergocalciferol (25 micrograms/d) for 6-72 mo followed by TPN containing amino acids with reduced Al and ergocalciferol (5 micrograms/d) for 9-58 mo. We also did a cross-sectional study of 22 patients receiving casein and ergocalciferol (25 micrograms/d) compared with 46 patients receiving amino acids and ergocalciferol (5 micrograms/d) for 6-58 mo. Bone formation was higher and osteoid area, bone-surface stainable Al and total bone Al were lower with amino acid TPN than with casein TPN. Bone formation varied inversely with both plasma Al and bone-surface Al, suggesting that plasma or bone-surface Al, acquired during TPN, can reduce bone formation and lead to patchy osteomalacia. Serum levels of iPTH and 1,25-dihydroxyvitamin D were higher with amino acid TPN.