A multicenter study on the effects of lanthanum carbonate (Fosrenol) and calcium carbonate on renal bone disease in dialysis patients

BACKGROUND

Lanthanum carbonate (LC) (Fosrenol) is a novel new treatment for hyperphosphatemia. In this phase III, open-label study, we compared the effects of LC and calcium carbonate (CC) on the evolution of renal osteodystrophy (ROD) in dialysis patients.

METHODS

Ninety-eight patients were randomized to LC (N = 49) or CC (N = 49). Bone biopsies were taken at baseline and after one year of treatment. Acceptable paired biopsies were available for static and dynamic histomorphometry studies in 33 LC and 30 CC patients. Blood samples were taken at regular intervals for biochemical analysis and adverse events were monitored.

RESULTS

LC was well tolerated and serum phosphate levels were well controlled in both treatment groups. The incidence of hypercalcemia was lower in the LC group (6% vs. 49% for CC). At baseline, subtypes of ROD were similarly distributed in both groups, with mixed ROD being most common. At one-year follow-up in the LC group, 5 of 7 patients with baseline low bone turnover (either adynamic bone or osteomalacia), and 4 of 5 patients with baseline hyperparathyroidism, had evolved toward a normalization of their bone turnover. Only one lanthanum-treated patient evolved toward adynamic bone compared with 6 patients in the CC group. In the LC group, the number of patients having either adynamic bone, osteomalacia, or hyperpara decreased overall from 12 (36%) at baseline to 6 (18%), while in the calcium group, the number of patients with these types of ROD increased from 13 (43%) to 16 (53%).

CONCLUSION

LC is a poorly absorbed, well-tolerated, and efficient phosphate binder. LC-treated dialysis patients show almost no evolution toward low bone turnover over one year (unlike CC-treated patients), nor do they experience any aluminum-like effects on bone.

Color Doppler ultrasound guidance during renal angioplasty and stenting

PURPOSE

To investigate whether an imaging technique combining color Doppler ultrasonography and selective renal artery digital subtraction angiography reduces contrast requirements in patients with progressive renal insufficiency undergoing renal artery angioplasty and stenting.

METHODS

Eight patients (5 men; mean age 58 years) with renal artery stenosis and renal insufficiency underwent percutaneous transluminal angioplasty and stenting under color Doppler ultrasound guidance.

RESULTS

Color Doppler ultrasound imaging yielded the information necessary for verifying catheter position, stent placement and expansion, and hemodynamics after revascularization. The combined imaging technique considerably reduced contrast requirements to only 10 mL in each case. No worsening of renal function was seen in any patient.

CONCLUSIONS

The combined imaging procedure uses low doses of contrast agent and is especially suited to patients with renal dysfunction undergoing percutaneous renal revascularization.

Atherosclerotic ischemic renal disease. Diagnosis and prevalence in an hypertensive and/or uremic elderly population

BACKGROUND

Atherosclerotic ischemic renal disease is a frequent cause of end-stage renal failure leading to dialysis among the elderly; Its prevalence is inferred from autopsy or retrospective arteriographic studies. This study has been conducted on 269 subjects over 50 with hypertension and/or CRF, unrelated to other known causes of renal disease.

METHODS

All 269 patients were studied either by color-flow duplex sonography (n = 238) or by renal scintigraphy (n = 224), and 199 of the 269 patients were evaluated using both of these techniques. 40 patients, found to have renal artery stenosis (RAS), were subjected to 3D-contrast enhancement Magnetic Resonance Angiography (MRA) and/or Selective Angiography (SA). An additional 23 cases, negative both to scintigraphy and to ultrasound study, underwent renal angiography (MRA and/or SA).

RESULTS

Color-duplex sonography, carried out in 238 patients, revealed 49 cases of RAS. MR or SA was carried out in 35 of these 49 patients, and confirmed the diagnosis in 33. Color-duplex sonography showed a PPV value of 94.3% and NPV of 87.0% while renal scintigraphy, carried out in 224 patients, had a PPV of 72.2% and a NPV of 29.4%. Patients with RAS showed a higher degree of renal insufficiency compared to non stenotic patients while there were no differences in proteinuria. RAS, based on color-duplex sonography studies, was present in 11% of patients in the age group 50-59, 18% in the 60-69 and 23% at age 70 and above.

CONCLUSIONS

A relatively large percentage of the elderly population with renal insufficiency and/or hypertension is affected by RAS and is at risk of developing end-stage renal failure. Color-duplex ultrasonography is a valid routine method of investigation of population at risk for renal artery stenosis.

PTH 1-84 and PTH "7-84" in the noninvasive diagnosis of renal bone disease

BACKGROUND

The intact parathyroid hormone (PTH) assay evaluates levels of serum 1-84 PTH and other N-terminally truncated PTH fragments, mainly PTH "7-84." This PTH molecule has been found experimentally to interfere with biological activity of PTH 1-84, perhaps through its binding to the PTH receptor complex. Therefore, assuming that high levels of PTH 7-84 are a cause of bone resistance to PTH, it has been hypothesized that a decreased 1-84 to 7-84 PTH ratio caused by a relative increase in PTH 7-84 level might help in the noninvasive diagnosis of low-turnover osteodystrophy (LTO).

METHODS

This study was performed in 35 patients with chronic renal failure on hemodialysis therapy who underwent bone biopsy for a histological, histomorphometric, and histodynamic study. In addition, blood samples were obtained for intact PTH, 1-84 PTH, and total PTH assays. PTH 7-84 level was obtained from the difference between total and 1-84 PTH assay results.

RESULTS

Nine patients had LTO (8 patients, adynamic bone disease; 1 patient, osteomalacia), 12 patients had hyperparathyroidism (HP), and 14 patients had mixed osteodystrophy (MO). On average, 1-84 PTH levels were approximately 60% of mean values for intact PTH. The two assays were strictly correlated. Average 1-84 to 7-84 PTH ratios were 1.57 +/- 0.85, 1.73 +/- 1.31, and 1.95 +/- 2.1 in the three histological groups (LTO, HP, and MO, respectively), with no significant difference.

CONCLUSION

Contrary to previous expectations, results do not favor the hypothesis of a role of 7-84 PTH in bone resistance in renal osteodystrophy. The 1-84 to 7-84 PTH ratio is not a marker of LTO and is of no use in noninvasive histological diagnosis.

Could an echo contrast agent be helpful in identifying renal artery stenosis?

BACKGROUND

Diagnosis of renal artery stenosis using echo color-Doppler is subjected to several limitations. The aim of this study was to examine if the routine use of a contrast agent could be helpful in identifying renal artery stenosis (RAS).

METHODS

We analysed 35 patients affected by RAS using an echo color-Doppler coupled with a contrast agent. All patients presented arterial hypertension, with a good drugs control, and mean serum creatinine of 1.8 mg/dL. All patients previously underwent angiography. RAS was at the origin of the artery in 27 patients, at the intermediate tract in 8. All patients had already been submitted to a basal echo color-Doppler.

RESULTS

The contrast agent determined a significant increase in the average colour signal in all the subjects, and a better evaluation of the spectral waveforms, if compared to the basal examination.

CONCLUSIONS

The results obtained showed that the contrast agent doesn't improve the diagnosis of RAS, especially in vascular origin stenosis, while it shows a real advantage in the intermediate or distal stenosis which are better visualized.

Renal osteodystrophy in predialysis and hemodialysis patients: comparison of histologic patterns and diagnostic predictivity of intact PTH

BACKGROUND

Comparison of renal osteodystrophy in predialysis and hemodialysis has been rarely reported. Distinct patterns of renal osteodystrophy could be found in these conditions. In addition the use of parathyroid hormone (PTH) and other markers for noninvasive diagnosis may result in different predictive values in predialysis and hemodialysis patients.

METHODS

79 consecutive patients with conservative chronic renal failure and 107 patients on hemodialysis were studied. All patients were subjected to bone biopsy for histological and histomorphometric evaluation. The patients had no exposure to aluminium before dialysis and relatively low exposure while on hemodialysis.

RESULTS

In the predialysis patients, bone biopsies showed 9 cases of adynamic bone disease (ABD) and 8 cases of osteomalacia (OM), 50 patients with mixed osteodystrophy and 2 cases of hyperparathyroidism. Among the hemodialysis patients 12 cases had ABD, 3 cases OM, 30 mixed osteodystrophy, and 61 patients hyperparathyroidism. In the predialysis patients with chronic renal failure, bone aluminium was on average 4.5 mg/kg dry weight, while in dialysis patients the average value was 35.4 mg/kg dry weight. Discriminant analysis of low turnover osteodystrophy (ABD and OM) by intact PTH showed higher accuracy in dialysis than in predialysis patients. Correlation studies of intact PTH versus bone formation rate, osteoblast surface/bone surface and osteoclast surface/bone surface showed significantly steeper slopes in dialysis than in predialysis patients, which indicates that bone resistance to PTH is more marked in predialysis patients.

CONCLUSIONS

The prevalence of ABD and OM in the geographic area investigated is lower than in other reports. Aluminium exposure does not seem to be the cause of low turnover osteodystrophy in the present population. The predictive value of intact PTH in the noninvasive diagnosis of renal bone disease is higher in hemodialysis patients than in predialysis patients. Predialysis chronic renal failure, when compared to the dialysis stage, seems to be characterized by resistance of bone tissue to PTH.

Urinary composition and lithogenic risk in normal subjects following oligomineral versus bicarbonate-alkaline high calcium mineral water intake

OBJECTIVE

A normal dietary calcium intake to reduce intestinal oxalate absorption is essential to avoid recurrence of calcium oxalate stone formation. It is also important in the prevention of osteopenia in idiopathic hypercalciuria. The calcium content of waters used for hydration may vary from very low to relatively high and is an important factor in prevention or additional risk of stone formation. Therefore, the effect of drinking mineral waters of different calcium concentrations on lithogenic risk factors was studied in normal volunteers.

MATERIALS AND METHODS

Normal subjects were divided into two groups of 11 and 10 individuals each. All followed a prescribed diet with an average calcium content of 800 mg/day. The water intake for hydration consisted of 2 liters of an oligomineral water with a low calcium content, <20 mg/l (group A) or of a bicarbonate alkaline water with a high calcium content, 370 mg/l (group B).

RESULTS

Diuresis increased similarly in both groups; urine calcium increased by about 80 mg/day in group B. A rise in urine oxalate was observed in both groups, along with the increased urine volume. Osmolar excretion increased in group B; urine osmolality decreased significantly only in group A. In spite of the increase in calciuria in group B, Ca/citrate ratio was constant, due to an increase in citrate excretion. Inter-group differences in terms of activity products of calcium phosphate, calculated according with Tiselius's methods, were found. The differences in AP(CaP) index 1 and AP(CaP) index 2 were significant, with higher values in group B, who drank the bicarbonate alkaline mineral water.

CONCLUSIONS

Increased water intake between meals to prevent renal stone recurrence should preferably be achieved with a relatively low calcium water and calcium-rich mineral waters should be avoided.

Serum osteoprotegerin and renal osteodystrophy

BACKGROUND

Numerous growth factors and cytokines are known to modulate bone turnover. An important, recently discovered complex involved in osteoclastogenesis is the osteoprotegerin/osteoprotegerin-ligand (OPG/OPGL) cytokine complex, which is produced by osteoblasts. Many factors, including parathyroid hormone (PTH), appear to affect bone turnover through this pathway. In this disorder, the role of the OPG/OPGL system in the pathogenesis of renal osteodystrophy, a disease with either low or high bone turnover, has not been investigated so far.

METHODS

Thirty-nine chronic haemodialysis patients had bone biopsies, including histomorphometric and histodynamic examinations. In addition, the following serum biochemistry parameters were measured: serum OPG, intact PTH, PTH 1-84, total PTH, osteocalcin, total and bone alkaline phosphatases, 25-hydroxycholecalciferol and 1,25-dihydroxycholecalciferol.

RESULTS

On average, serum OPG levels were above the normal range. They were lower in adynamic bone disease (ABD) patients, than in patients with predominant hyperparathyroidism (HP) or mixed osteodystrophy (MO). Significant negative correlations were found between serum OPG and PTH levels, and between serum OPG and parameters of bone resorption (ES/BS) and bone formation (ObS/BS and BFR/BS) in HP and MO patients with PTH values < or =1000 pg/ml. For intact PTH levels < or =300 pg/ml, serum OPG was significantly lower in the group with ABD than in those with HP or MO (P<0.05).

CONCLUSION

In renal osteodystrophy the OPG/OPGL system is involved in the regulation of bone turnover induced by PTH. The determination of serum OPG levels could be of use in the diagnosis of low turnover bone disease, at least in association with PTH levels < or =300 pg/ml.

Parathyroidectomy in chronic renal failure: short- and long-term results on parathyroid function, blood pressure and anemia

To evaluate the long-term results of parathyroidectomy (PTX) on parathyroid function, blood pressure and anemia, data of 45 patients with secondary Hyperparathyroidism in dialysis who had undergone PTX were collected retrospectively from 8 different dialysis units. The patients, 25 M and 20 F, mean age 56 +/- 11 years, who were followed up for an average period of 3.3 +/- 2.3 years, were divided into four groups according to the surgical procedure: 19 patients had had a subtotal PTX; 10 patients had undergone total PTX with autotransplantation (AT); 10 patients had had total PTX without AT, and 6 patients had undergone partial PTX. Taking a reduction in intact PTH > 50% as sign of successful PTX, only 5 patients did not attain this result. Considering values of PTH between 20 and 200 pg/ml at the mid-term observation (1-2 years) as the optimal result, values under 20 pg/ml as an expression of permanent hypoparathyroidism, and those above 200 pg/ml as indicating persistent/recurrent hyperparathyroidism, 65.5% of patients operated with subtotal PTX and total PTX + AT had a therapeutic success, versus 31.2% of patients in the other two groups, due to excess permanent hypoparathyroidism and persistent/recurrent hyperparathyroidism; 20 of 45 patients with preoperative hypertension experienced a statistically and clinically significant decrease in blood pressure levels. An increase in serum hemoglobin was also observed, despite a reduction of administered erythropoietin. In conclusion, the results of PTX obtained from this multicenter study are comparable to those reported by single leading centers. Recommended surgical procedures are subtotal PTX and total PTX with AT. The fall in blood pressure in hypertensive patients is clinically significant, and improvement in anemia is also observed with a reduction in erythropoietin dosage.

Histomorphometric assessment of bone turnover in uraemic patients: comparison between activation frequency and bone formation rate

AIMS

The histomorphometric assessment of bone formation rate (BFR/BS) in bone biopsies from uraemic patients is of crucial importance in differentiating low from high turnover types of renal osteodystrophy. However, since BFR/BS relies on osteoblasts, activation frequency (Ac.f), encompassing all remodelling phases, has recently been preferred to BFR/BS. This study was carried out to consider whether estimation of Ac.f is superior, in practical terms, to that of BFR/BS in distinguishing between different rates of bone turnover in uraemic patients.

METHODS AND RESULTS

Bone biopsies from 27 patients in predialysis (20 men and seven women; mean age 53 +/- 12 years) and 37 in haemodialysis (22 men and 15 women; mean age 53 +/- 12 years) were examined. The types of renal osteodystrophy were classified on the basis of morphology. Bone formation rate and Ac.f were evaluated according to standardized procedures. The Ac.f was calculated both as a ratio between BFR/BS and wall thickness (W.Th) and as a reciprocal of erosion, formation and quiescent periods (EP, FP and QP). Patients were affected by renal osteodystrophy with predominant hyperparathyroidism (two predialysis and 16 dialysis), predominant osteomalacia (three predialysis and seven dialysis) or that of advanced (nine predialysis and five dialysis) or mild (seven predialysis and four dialysis) mixed type or adynamic type (six predialysis and five dialysis). Activation frequency, which with either formula requires the measurement of W.Th, i.e. the thickness of bone structural units (BSUs), was not calculated in three dialysis patients with severe hyperparathyroidism and in one predialysis and four dialysis patients with severe osteomalacia, because only incomplete BSUs were found. In dialysis, EP was higher in the adynamic than in the other types of osteodystrophy. During both predialysis and dialysis, FP was higher in osteomalacia than in the other forms of osteodystrophy, and in adynamic osteopathy than in hyperparathyroidism or in advanced and mild mixed osteodystrophy. During predialysis and dialysis, QP was higher in the adynamic than in the other forms of osteodystrophy. Correlations were found between BFR/BS and Ac.f, during predialysis (r=0.97) and dialysis (r=0.95).

CONCLUSIONS

The superiority of Ac.f in assessing bone turnover, in comparison to BFR/BS, is conceptual rather than practical. The highest values for FP in osteomalacia and for QP in adynamic bone allow a clearer characterization of these low turnover conditions.

Calcitriol per os once, twice or three times a week: effect of different schedules of administration in hemodialysis patients

Administration of a single dose of 1,25-OH(2)D(3) can lower PTH levels for up to 4 days in chronic hemodialysis patients. Our purpose was to verify the effects of the same weekly dose of calcitriol per os given in one, two or three administrations, to patients on dialysis with secondary hyperparathyroidism. Thirty patients were studied, divided in to three groups each of 10 patients. Calcitriol therapy in group A was given as a single weekly dose of 0.08 microg/kg b.w. In group B the same total weekly dose was divided in two equal doses. In group C the same total weekly dose was divided in three times. Treatment lasted 2 months. After 8 weeks of therapy the fall in intact PTH was statistically significant in each group, respectively with one-way ANOVA: p<0.02 (A); p<0.002 (B); p<0.001 (c). Two-way ANOVA for comparison of PTH % variation among the three groups was statistically significant p<0.003. Significance was due to difference between group A and groups B and C. The present study confirms the efficacy of single dose in suppressing significantly intact PTH. However, when the same weekly dose is divided into two or in three time-spaced administrations, the suppressive effects are definitely increased.

Ischemic nephropathy in an elderly nephrologic and hypertensive population

BACKGROUND

Atherosclerotic renovascular disease is a frequent cause of end-stage renal failure leading to dialysis in the elderly population. Its prevalence is known from autopsy or retrospective arteriographic investigations. This prospective study was conducted in 133 subjects with the inclusion criteria of hypertension and/or chronic renal failure starting after 50 years of age. Renal failure was unrelated to other known causes of renal disease.

METHODS

The patients were subjected to echo-color doppler ultrasonography of renal arteries (104) and/or to renal scintigraphy (112). Thirteen of 27 patients with positivity using one or both noninvasive techniques were subjected to digital selective angiography.

RESULTS

All the patients with positivity of echo-color doppler technique were true positives, with a consequent predictive value reaching 100%. Renal scintigraphy was of markedly lower predictive value. Based on the echo-color doppler investigation, percentage positivity for hemodynamically significant stenosis (> 50%) was 3.2 (16.3% had mild nonsignificant stenosis of renal arteries) in the 50- to 59-year-old group, 20% (plus 12.5% with nonsignificant stenosis) in the 60- to 69-year-old group and 25% (plus 17.8% nonsignificant stenosis) in the > 70-year age group. Patients with significant stenosis also had a significantly higher degree of renal insufficiency and received a higher number of hypotensive drugs (p < 0.013). The percentage of hypertensive patients was not different in the stenotic and nonstenotic groups.

CONCLUSIONS

A large percentage of the elderly population is affected by renal vascular obstructive disease and is at risk of developing end-stage renal failure. Considering the wide number of cases with foreseeable renal arterial stenosis in the vast population meeting the selection criteria, it is possible to conclude that not all cases evolve to renal failure due to different rates of progression or to untimely nonrenal death.

Urinary deoxypyridinoline excretion for the evaluation of bone turnover in chronic renal failure

BACKGROUND

The urinary excretion of deoxypyridinoline (DPD) was evaluated in predialysis chronic renal failure (CRF), together with intact PTH and several classic markers of bone turnover in order to assess whether urine free and total DPD excretion are equivalent parameters of bone turnover in CRF, and to evaluate the relationship between urine DPD excretion, PTH and the other bone markers.

METHODS

The study was carried out in 94 patients with different degrees of renal failure due to various kidney diseases. Besides urinary DPD expressed as free DPD, total DPD, free/total DPD, free DPD/Cr and total DPD/Cr, the following determinations were made: intact PTH, bone alkaline phosphatase (BALP), total alkaline phosphatase (AP), osteocalcin (BGP), serum C-terminal telopeptide of collagen type I (ICTP) and hydroxyproline (OHpro). The patients were divided into 3 groups according to the increasing severity of renal failure (Ccr >40, 40-20, <20 ml/min).

RESULTS

The ratio free/total DPD decreased (NS) with advancing renal failure, and was inversely correlated with total DPD excretion. While PTH increased progressively to about four times the values observed in the Ccr >40 group, there was a parallel increase only in BGP and ICTP, parameters retained in the serum with decreasing renal function, while AP, BALP, total DPD and OHpro did not change. However, significant correlations between total DPD/Cr and PTH, BALP, BGP and ICTP were also found.

CONCLUSIONS

In CRF free DPD is an unreliable index of bone turnover due to a probable interference in its production from the peptide-bound DPD. Total DPD or total DPD/Cr are better used. In spite of the significant correlations observed in advanced renal failure between PTH and most of the parameters examined, a resistance of bone tissue to PTH action in CRF must be considered.

Changes in bone turnover after parathyroidectomy in dialysis patients: role of calcitriol administration

BACKGROUND

Available data on changes in serum levels of bone markers after parathyroidectomy (PTx) in dialysis patients are not uniform. Changes are thought to be due to either a reduction in PTH activity per se or to a direct effect of vitamin D therapy on bone cells. We aimed to verify whether treatment with vitamin D modifies serum levels of markers of bone synthesis (alkaline phosphatase (AP), osteocalcin (BGP), procollagen type I C-terminal peptide (PICP)) and resorption (collagen type I C-terminal peptide (ICTP)) within a period of 15 days in haemodialysis patients with severe secondary hyperparathyroidism following PTx.

METHODS

We randomized two groups (A, treatment and B, placebo, 10 patients each) with comparable basal PTH values and measured bone markers 3, 7 and 15 days after surgery. All patients were treated with calcium supplements (i.v. and p.o.), and group A also received calcitriol (2.4+/-1.0 microg/day, p.o.).

RESULTS

In both groups, PTx induced significant changes in all the markers evaluated, except for BGP in group B. Compared to basal values, ICTP decreased from 481+/-152 ng/ml in group A and 277+/-126 ng/ml in group B to 267+/-94 and 185+/-71 ng/ml (M+/-SD) respectively, and PICP increased from 307+/-139 ng/ml in group A and 309+/-200 ng/ml in group B to 1129+/-725 and 1231+/-1267 ng/ml (M+/-SD) respectively, within 3 days of surgery. AP values increased after 15 days from 1115+/-734 mU/ml in group A and 1419+/-1225 mU/ml in group B to 1917+/-1225 and 1867+/-1295 mU/ml (M+/-SD) respectively. On the contrary, mean values of BGP were never different from basal levels after PTx in either group. In the two groups, the pattern of changes of all the bone markers after PTx was almost identical. Group A patients predictably required lower doses of oral calcium supplements to correct hypocalcaemia (16. 9+/-5.7 vs 22.1+/-5.0 g/10 days; M+/-SD, P<0.04).

CONCLUSIONS

The opposite behaviour of serum PICP and ICTP after PTx, in both the treated and untreated groups suggests that quantitative uncoupling between bone synthesis and resorption is responsible for hypocalcaemia. This phenomenon, as reflected by the evaluated bone markers, is unaffected by calcitriol. Based on our data we conclude that immediately after parathyroid surgery, vitamin D therapy does not influence bone cell activity, but improves hypocalcaemia mainly through its known effect on intestinal calcium absorption.

Who are the non-dippers? A better definition via the blood pressure circadian rhythm

OBJECTIVE

The non-dipping phenomenon (NDP) can be better interpreted when considering that blood pressure (BP) shows a within-day variability which is the expression of a circadian rhythm (CR).

PATIENTS AND METHODS

The NDP was investigated at the light of the BP CR by analysing the ambulatory BP monitoring of 298 essential hypertensive patients (EHP), 84 secondary hypertensive patients (SHP), as well as 93 normotensive subjects (NS). According to the rhythmometric validation, the investigated subjects were defined "rhythmic" (R) or "non-rhythmic" (NR).

RESULTS

The non-dippers (ND) were found among not only the EHP (14%) and SHP (27%) but also the NS (16%). The percentages of R ND were 9%, 4% and 20%, respectively in EHP, SHP and NS. The R ND were characterized by a nocturnal phase-shift (100% in NS), associated with an amplitude increase (50% in EHP) or a mesor increase (50% in EHP; 100% in SHP) in BP CR. The NR ND were characterized by an amplitude almost negligible (100% in NS) associated with a mesor increase (100% in EHP; 100% in SHP).

CONCLUSIONS

The detection of a NDP associated with a rhythmicity suggests that the criterion with which the ND are identified cannot be used for making inferences on the BP CR in HP or NS. The rhythmic characteristics in ND suggest that the rhythmometric analysis is fundamental for identifying the abnormal time structure of BP 24-h values in the presence of the NDP.

Bone markers in the diagnosis of low turnover osteodystrophy in haemodialysis patients

BACKGROUND

Renal osteodystrophy includes a number of low and high turnover bone histologic patterns which require a bone biopsy for their full identification. The role of intact PTH and several classical and more recent bone markers in the non-invasive diagnosis of renal bone disease in patients with CRF in HD requires further definition since available published data are limited.

METHODS

In addition to intact PTH, alkaline phosphatase (AP) and osteocalcin (BGP), bone alkaline phosphatase isoenzyme (BALP), tartrate resistant acid phosphatase (TRAP), C-terminal cross-linked peptide of collagen type 1 (ICTP) and deoxypyridinoline (DPD) were measured in the serum of 41 patients on haemodialysis, subjected at the same time to transiliac bone biopsy for histomorphometric, histodynamic and aluminium histochemical examination. Histodynamic evaluation following double tetracycline label, was carried out in 37 patients. The patients had no evidence of active cytolytic and cholestatic liver disease and a history of very limited aluminium exposure.

RESULTS

The patients had differing degrees of hyper-parathyroidism, with intact PTH ranging from normal to very elevated levels. Serum values of the markers BGP, ICTP and DPD, normally excreted through the kidneys, were on average very high. The correlation coefficients of the humoral parameters vs dynamic variables, such as BFR/BS, were high. The highest values were: intact PTH 0.798, AP 0.900, BALP 0.891, ICTP 0.807. The patients, grouped in low turnover osteodystrophy (LTO; 9), mixed osteodystrophy (MO; 9) and prevalent hyperparathyroidism (HP; 23), showed significant difference in the levels of most humoral and static and dynamic parameters (ANOVA). Bone aluminium histochemistry was negative in all cases. Discrimination of LTO patients from the other groups by humoral parameters, at the highest value of accuracy, showed 100% sensitivity and 93.7% specificity with a cut-off of 12.9 ng/ml for BALP; 88.9% sensitivity and 93.7% specificity with a cut-off of 21.5 ng/ml for DPD, and 88.9% sensitivity and 90.6% specificity with a cut-off of 79.7 pg/ml for intact PTH. The other markers had lower values. A standardized z-score approach for evaluation of all humoral parameters was also carried out. Using all variables, a correct classification of MO/HP and of LTO was possible in 93.8 and 88.9% of the cases, respectively. Predictive power was 96.8 and 80%, respectively for MO/HP and LTO. When the only variables used were intact PTH and BALP, a correct classification of MO/HP and LTO was possible in 90.6% and 88.9%, respectively. Predictive value of MO/HP was 96.7% and for LTO 72.7%. Predictive values using PTH and AP were 96.3% and 57.2%, respectively.

CONCLUSION

Intact PTH and several relatively new bone markers are of certain value in the non-invasive diagnosis of renal osteodystrophy. However some of the humoral markers carry the same quality of information and the use of intact PTH and BALP may be adequate in the discrimination of bone histologic patterns. In cases exempt from liver disease, PTH and AP may be used as a less costly alternative. Bone biopsy could be chiefly limited to cases with borderline humoral values and to all those with a suspected aluminium overload.

Relative roles of intestinal absorption and dialysis-fluid-related exposure in the accumulation of aluminium in haemodialysis patients

BACKGROUND

A recent retrospective study has clearly demonstrated a reduction of cases with positive bone aluminium (Al) staining in the Italian dialysis population, which in general has had a low prevalence of bone Al toxicity. In the present study we tried to better address the relative role played, in our study population, by enteral and parenteral exposure to Al in reducing bone accumulation.

METHODS

We retrospectively examined the data of 105 DFO tests and bone Al determinations performed in dialysis patients from 1984 to 1995. Enternal exposure was analysed by accurate anamnestic records, while parenteral exposure was evaluated by the determination of Al content in dialysis fluids. Bone Al content was assayed chemically and histochemically, while serum Al was assayed spectrophotometrically. Data pertinent to the patients were allotted into three period groups: 1984-1987; 1988-1991; 1992-1995. As for Al concentrations in dialysis fluids, the interval 1980-1983 (immediately before the start of our study), which could clearly have influenced bone Al content, was also considered.

RESULTS

Basal serum Al showed some fluctuations (42.7 +/- 34.1; 24.8 +/- 21.9 and 38.9 +/- 34.9 micrograms/l respectively in the three groups, ANOVA P < 0.01) but only values of the period 1988-1991 were significantly lower than those of the period 1984-1987 (P < 0.05). Increments after DFO did not differ in the three periods (136.5 +/- 105.7; vs 98.7 +/- 91.7 and 106.1 +/- 96.2 micrograms/l respectively, P = n.s.). Enteral exposure to drugs containing Al was comparable (4.1 +/- 2.9 vs 4.0 +/- 4.6 and 5.8 +/- 7.9 total kg ingested respectively; P = n.s.), but bone Al was dramatically reduced (from 60.7 +/- 43.0 to 29.0 +/- 24.4 and 31.9 +/- 29.9 mg/kg/dw respectively; P < 0.0001), along with the definite disappearance of Aluminon-positive cases and Al-related bone disease (ARBD) after 1991. Parenteral exposure through the dialysate dropped from a mean of 26 +/- 14 micrograms/l in the 4-year period prior the start of the study (1980-1983) to 9 +/- 6 micrograms/l in the period 1984-1987 and to 4.9 +/- 2.1 micrograms/l and 5.0 +/- 2.0 micrograms/l respectively thereafter (P < 0.0001).

CONCLUSIONS

Despite the persistence of oral exposure to Al, responsible for the observed stability of serum Al levels, a definite reduction of bone Al content has been recorded in our dialysis population, and ARBD has disappeared. This result has to be referred essentially to the optimal control of Al content in dialysis fluids, which is confirmed as a major factor for Al intoxication.

Renal bone disease in 76 patients with varying degrees of predialysis chronic renal failure: a cross-sectional study

BACKGROUND

Renal osteodystrophy has been studied less extensively in predialysis than in dialysis patients. Different types or histological patterns in their natural evolution from moderate to advanced severity of renal insufficiency are only partially known, with special regard to adynamic bone disease and its relationship with osteomalacia.

METHODS

We conducted a cross-sectional retrospective study on 76 unselected patients with chronic renal failure undergoing conservative treatment, with a wide range of severity of renal insufficiency. All the patients were subjected to bone biopsy for histological and histomorphometric evaluation. The patients, 44 males and 32 females ranging in age from 18 to 72 years and with serum creatinine 1.2-11.4 mg/dl, had not been exposed to aluminium-containing drugs and had never been treated with vitamin D or calcitriol.

RESULTS

Ten patients had normal bone, nine were diagnosed with adynamic bone disease, 26 with mild mixed osteodystrophy, seven with predominant osteomalacia, 22 with advance mixed osteodystrophy, and two with predominant hyperparathyroidism. Patients with adynamic bone disease had less severe chronic renal failure than the other pathological subgroups, intact PTH above the upper limit of normal, normocalcaemia, and reduced serum osteocalcin in line with a significantly lower ObS/BS. Osteomalacia was found in a more advanced stage of chronic renal failure with relative hypocalcaemia and more severe metabolic acidosis. A creatinine clearance of 20 ml/min served as a clear demarcation between this histological group and adynamic bone disease.

CONCLUSIONS

It is postulated that adynamic bone disease is a form of renal osteodystrophy, separate from osteomalacia, appearing when bone resistance to PTH develops, probably a transient stage to more hyperparathyroid histological classes with increasing severity of chronic renal failure.

Fracturing osteoporosis after kidney transplantation--what are the options?

The patient who receives a renal graft does not have virgin bones. Renal transplantation must be performed in a patient with pre-existing bone disease, i.e. renal osteodystrophy, characterized by secondary hyperparathyroidism, calcitriol deficiency, phosphate retention, metabolic acidosis and possibly aluminium accumulation. These pathomechanisms are further modulated by factors such as duration of dialysis, type of dialysis, diet, control of serum phosphate, use phosphate-binding agents etc.

Extent of alkaline phosphatase cytochemistry vs. extent of tetracycline fluorescence in the evaluation of histodynamic variables of bone formation

Alkaline phosphatase (ALP) activity is a new histomorphometric index of the extent of osteoblastic surfaces involved in mineralization. To assess its validity in the evaluation of bone formation, we carried out a comparative study between histomorphometric values obtained on the basis of the extent of tetracycline labeling and of the length of ALP-positive endosteal surfaces. The following variables were compared (indicated by ALP when based on the extent of ALP positivity): trabecular mineralizing surface (MS/BS vs. ALP.S/BS); osteoid mineralizing surface (MS/OS vs. ALP.S/OS); bone formation rate (BFR/BS vs. ALP.BFR/BS); and adjusted appositional rate (Aj.AR vs. ALP.Aj.AR). Bone biopsies from 39 patients with chronic renal failure and different types of renal osteodystrophy were considered (48 +/- 12 years of age; 19 men and 20 women). Patients were double labeled with tetracycline and biopsies were embedded in glycol-methacrylate at +4 degrees C. Patients showed various types of renal osteodystrophy and were assigned to different groups of pathologies. Although it differed in incidence according to the different groups, ALP activity was found in typical plump osteoblasts bordering osteoid seams and in flat cells, either in contact with osteoid or along the quiescent surfaces of bone in continuity with it. Tetracycline codistributed with all these features to variable extents, according to groups. In all patients, however, ALP.S/BS and ALP.S/OS respectively exceeded MS/BS and MS/OS. In consequence of this, ALP.BFR/BS and ALP.Aj.AR were greater than BFR/BS and Aj.AR, respectively. For each of the variable considered, differences among groups of patients with different types of renal osteodystrophy were highly significant. Good correlations were found between the variables measured with the two methods.(ABSTRACT TRUNCATED AT 250 WORDS)

Intravenous versus oral calcitriol therapy in renal osteodystrophy: results of a prospective, pulsed and dose-comparable study

Intravenous calcitriol is generally considered to be more efficient than oral administration in the treatment of secondary hyperparathyroidism of chronic renal failure, although a comparative and prospective study employing the same doses and modality of drug administration is lacking. We therefore evaluated 12 hemodialysis (HD) patients (51.7 +/- 9.4 years, mean +/- SD, HD for 8.7 +/- 4.7 years) with marked secondary hyperparathyroidism. Based on basal humoral and bone histologic parameters, we divided these patients into 2 comparable groups. Calcitriol (0.015 micrograms/kg) was given at the end of each dialysis intravenously in group A and orally in group B. Humoral parameters were evaluated basally and after 1, 2, 4 and 8 months. Ax bone biopsy was taken at the start and at the end of the study. From the first month of treatment, group A showed an increment in ionized calcium (from 1.28 +/- 0.08 to 1.37 +/- 0.12 mmol/l, p < 0.01), with a reduction in intact parathyroid hormone (from 470.1 +/- 349.5 to 255.5 +/- 256.5 pg/ml; p < 0.0003) and alkaline phosphatase (from 615.1 +/- 696.3 to 445.3 +/- 577.7 mU/ml, p < 0.001). The occurrence of hypercalcemia prompted a reduction in dialysate calcium content in 4 of 6 patients after 4 months, and of the calcitriol dose in 2 of 4 patients after 6 months. Ionized calcium then turned to 1.32 +/- 0.11 (p = n.s. compared to basal) while the intact parathyroid hormone concentration tended to revert (363.3 +/- 360 pg/ml, p = n.s. compared to basal) and alkaline phosphatase remained low (420 +/- 638 mU/ml, p < 0.0005).(ABSTRACT TRUNCATED AT 250 WORDS)

Procollagen type 1 C-terminal extension peptide serum levels following parathyroidectomy in hyperparathyroid patients

Procollagen type 1 is mainly synthesized by osteoblasts and, after cleavage of the N- and C-terminal extension peptides, is utilized for collagen fibril deposition in the osteoid tissue. Serum levels of C-terminal extension peptide (Pcoll-1-C) of the procollagen molecule has been considered a useful marker for the evaluation of the rate of osteoblastic procollagen synthesis. To appraise whether in vivo parathyroid hormone (PTH) plays a suppressive role in the synthesis of procollagen type 1, a study has been carried out in 16 patients, 10 with severe secondary hyperparathyroidism of chronic renal failure and 6 with primary hyperparathyroidism. Following parathyroidectomy (PTX), in chronic renal failure patients a 94% fall in serum intact iPTH and a decline of serum calcium to hypocalcemic levels requiring calcitriol administration were observed. Serum Pcoll-1-C increased markedly with a peak after 7 days and a subsequent decline. Similar changes were observed for alkaline phosphatase and osteocalcin. In primary hyperparathyroidism, PTX was followed by an 88% drop in iPTH and mild hypocalcemia not requiring calcitriol administration. Also in this group serum Pcoll-1-C increased significantly with the same time course, unaccompanied by changes in alkaline phosphatase and osteocalcin. In 4 unsuccessfully neck-operated control patients no change in serum Pcoll-1-C levels was recorded during a period of 2 weeks postoperatively. In conclusion, acute withholding of parathyroid hypersecretion is accompanied by an abrupt and transitory increase of serum Pcoll-1-C, not dependent on calcitriol administration. Hypocalcemia following PTX may in part be due to uncoupling of bone formation and resorption.