Diagnosis and monitoring of renal osteodystrophy

Fibrous osteodystrophy due to secondary renal hyperparathyroidism in a senile dog

ABSTRACT Renal hyperparathyroidism stands out among the complications of kidney disease in dogs due to phosphorus retention with a predisposition to hypocalcemia, parathyroid hormone stimulation with mobilization of calcium from the bones, characterizing fibrous osteodystrophy, unusual in the elderly. The objective was to report it in 12-year-old Labrador with polyuria, polydipsia, and emesis for five months due to maxillary and mandibular volume increase, followed by loosely fixed teeth, and facial deformity. Blood tests showed anemia, thrombocytosis, azotemia, hypoalbuminemia and hyperphosphatemia and urinalysis showed low density, glycosuria, proteinuria, and moderate caudate and transitional epithelial cells. Oral x-rays showed loss of dental bone support and decreased bone radiopacity. Chest radiographs showed decreased density in the ribs and costochondral junction; on the other hand, organs of the cardiorespiratory system showed no changes. The electrocardiogram and echocardiogram did not show impairment. Abdominal ultrasound revealed kidneys with asymmetry, increased echogenicity of the cortical and poorly preserved cortico-medullary definition. Oral histopathology showed intense fibroplasia associated with bone reabsorption. Support therapy was instituted, but the patient died ten days after consultation. Thus, although uncommon in the elderly, fibrous osteodystrophy should be investigated in dogs with advanced-stage chronic kidney disease and, even with conservative therapies, the prognosis is unfavorable.

Effect of aluminum on markers of bone formation resorption in chronic hemodialysis patients

Background: T`he prevalence of aluminum (Al)-related toxicity in hemodialysis (HD) patients has declined. However, some HD patients continue to receive Al-based phosphate binders, in part because of the expense of Al-free binders.

Objective: To explore the effect of Al-based binders and their discontinuation on iron status, and markers of bone formation resorption in HD patients.

Methods: Following an initial screen of serum Al levels in 37 HD patients, a second screening was performed after discontinuation of Al-based binders in a 2-year follow-up. A desferrioxamine (DFO; 5 mg/kg) test, and assessment of iron status and bone markers were conducted in the second screening.

Results: Mean serum Al level was initially 27.8 ± 10.3 μg/L. Thirteen patients had a serum Al >30 μg/L, a level considered possibly toxic. There was a positive correlation between serum Al levels, HD duration, and cumulative dose of Al-based binder. At the second screening, the mean serum Al level decreased to 12.5 ± 7.4 μg/L. The mean serum Al level increased to 26.0 ± 14.7 μg/L post-DFO, but in none of the patients did the change in serum Al exceed the 50 μg/L threshold associated with Al-induced bone disease. The decrease in serum Al level was associated with a significant increase in intact parathyroid hormone (iPTH) whereas total alkaline phosphatase did not change.

Conclusions: We recommend that if Al-based phosphate binders are used in HD patients, serum Al level, iron, and markers of bone formation resorption be closely monitored to ensure safe use of these drugs.

Disparities in dialysis treatment and outcomes for Dutch and Belgian children with immigrant parents

BACKGROUND

In Belgium and the Netherlands, up to 40% of the children on dialysis are children with immigrant parents of non-Western European origin (non-Western). Concerns exist regarding whether these non-Western patients receive the same quality of care as children with parents of Western European origin (Western). We compared initial dialysis, post-initial treatment, and outcomes between non-Western and Western patients on dialysis.

METHODS

All children <19 years old on chronic dialysis in the Netherlands and Belgium between September 2007 and May 2011 were included in the study. Non-Western patients were defined as children of whom one or both parents were born in non-Western countries.

RESULTS

Seventy-nine of the 179 included patients (44%) were non-Western children. Compared to Western patients, non-Western patients more often were treated with hemodialysis (HD) instead of peritoneal dialysis (PD) as first dialysis mode (52 vs. 37%, p = 0.046). Before renal transplantation, non-Western patients were on dialysis for a median (range) of 30 (5-99) months, vs. 15 (0-66) months in Western patients (p = 0.007). Renal osteodystrophy was diagnosed in 34% of non-Western vs. 18% of Western patients (p = 0.028). The incidence rate ratio [95% confidence interval] for acute peritonitis was 2.44 [1.43-4.17] (p = 0.032) for non-Western compared to Western patients.

CONCLUSIONS

There are important disparities between children on chronic dialysis with parents from Western European origin and those from non-Western European origin in the choice of modality, duration, and outcomes of dialysis therapy.

Prevalence of radiological findings among cases of severe secondary hyperparathyroidism

CONTEXT AND OBJECTIVE

Patients with end stage renal disease (ESRD) and secondary hyperparathyroidism (HPT2) are prone to develop heterotopic calcifications and severe bone disease. Determination of the sites most commonly affected would decrease costs and patients' exposure to X-ray radiation. The aim here was to determine which skeletal sites produce most radiographic findings, in order to evaluate hemodialysis patients with HPT2, and to describe the most prevalent radiographic findings.

DESIGN AND SETTING

This study was cross-sectional, conducted in one center, the Hospital Universitário Clementino Fraga Filho (HUCFF), in Rio de Janeiro, Brazil.

METHODS

Whole-body radiographs were obtained from 73 chronic hemodialysis patients with indications for parathyroidectomy due to severe HPT2. The regions studied were the skull, hands, wrists, clavicles, thoracic and lumbar column, long bones and pelvis. All the radiographs were analyzed by the same two radiologists, with great experience in bone disease interpretation.

RESULTS

The most common abnormality was subperiosteal bone resorption, mostly at the phalanges and distal clavicles (94% of patients, each). 'Rugger jersey spine' sign was found in 27%. Pathological fractures and deformities were seen in 27% and 33%, respectively. Calcifications were presented in 80%, mostly at the forearm fistula (42%), abdominal aorta and lower limb arteries (35% each). Brown tumors were present in 37% of the patients, mostly on the face and lower limbs (9% each).

CONCLUSION

The greatest prevalence of bone findings were found on radiographs of the hands, wrists, lateral view of the thoracic and lumbar columns and femurs. The most prevalent findings were bone resorption and ectopic calcifications.

Mineral metabolism, bone histomorphometry and vascular calcification in alternate night nocturnal haemodialysis

BACKGROUND

Poor control of bone mineral metabolism (BMM) is associated with renal osteodystrophy and mortality in dialysis-dependent patients. The authors explored the efficacy of alternate nightly home haemodialysis (ANHHD) in controlling BMM parameters and its effects on bone mineral density and histomorphometry.

METHODS

In this prospective observational study, 26 patients on home haemodialysis (3-5 h, 3.5-4 sessions weekly) were converted to ANHHD (6-9 h, 3.5-4 sessions weekly). Biochemical parameters of BMM at baseline, 6 and 12 months, radiological parameters at baseline and 12 months and bone histomorphometry at 12 months are described.

RESULTS

Pre-dialysis serum phosphate fell from 2.13+/-0.65 to 1.38+/-0.35 mmol/L; P<0.0001. No binders were required in 77.2% compared with 7.7% at baseline. Calcium-phosphate product fell from 5.28+/-1.64 to 3.42+/-0.88 mmol2/L2; P<0.0001 and parathyroid hormone (PTH) from 301 (110-471) to 127 (47-240) ng/L; P=0.01. Bone mineral density remained stable. Vascular and ectopic calcification improved or stabilized in 87.5%. Bone histomorphometry at 12 months showed high, normal and low bone turnover in 10, 3 and 4 patients, respectively, with 6/17 patients having abnormal mineralization.

CONCLUSION

Alternate nightly home haemodialysis effectively manages biochemical parameters of BMM. Patients with very high PTH at baseline (>1000 ng/L) did not significantly improve parathyroid hormone status. Abnormal bone turnover and mineralization were present in a significant proportion of patients at 12 months but low turnover was uncommon. Vascular calcification was stabilized or improved in the majority. ANHHD compares favourably with every night and short daily therapy in relation to BMM management and may offer lifestyle advantages for patients.

Measurement of PTH Fragments for Assessment of Renal Bone Disease in Hemodialysis Patients

BACKGROUND

Renal bone pathology involves a spectrum from 'high-turnover' to 'low-turnover bone disease' (adynamic bone disease, classical osteomalacia). The diagnosis of the latter usually requires bone biopsy. Inhibitory parathyroid hormone (PTH) fragments may be useful for its noninvasive diagnosis.

METHODS

A cross-sectional study was performed in 54 patients on chronic hemodialysis which involved measurements of intact PTH (iPTH; Nichols assay), total PTH (tPTH; Scantibodies assay), and the cyclase-activating PTH fragment (CAP). The level of cyclase-inactive PTH fragment (CIP) was calculated. At the same time, serum calcium, phosphorus, and alkaline phosphatase levels as well as the current therapy for secondary hyperparathyroidism were recorded. In selected patients, bone radiographs were evaluated for osteitis fibrosa.

RESULTS

A high correlation (r = 0.94) was found between iPTH and tPTH, with the tPTH levels being lower by 30-40%. A similar association was also found for CAP (r = 0.988) and for CIP (r = 0.93). 3 out of the 54 patients had a CAP/CIP ratio of < or =1 which has been associated with adynamic bone disease. A higher CIP ratio was significantly associated with the use of aluminum-hydroxide- and calcium-containing phosphate binders.

CONCLUSIONS

iPTH and tPTH assays are highly correlated. In a general hemodialysis patient population, low-turnover bone disease appears to be rare, when the CAP/CIP ratio is used as a marker. A high CIP value was associated with therapy using aluminum hydroxide, a drug known to carry a risk of adynamic bone disease.

Localized jaw enlargement in renal osteodystrophy: report of a case and review of the literature

Renal osteodystrophy is a common long-term complication of end-stage renal disease. Involvement of the jaws is common and radiographic alterations are often one of the earliest signs of chronic renal disease. However, marked enlargement of the jaws is a rare complication of renal osteodystrophy. A case of localized asymptomatic enlargement of the mandible in a 38-year-old woman with chronic renal failure is presented. The clinical, radiographic, and histological findings were consistent with renal osteodystrophy. To our knowledge, this is the third case of localized mandibular enlargement of renal osteodystrophy reported in the English-language literature.

Imaging of renal osteodystrophy

Chronic renal insufficiency, hemodialysis, peritoneal dialysis, renal transplantation and administration of different medications provoke complex biochemical disturbances of the calcium-phosphate metabolism with wide spectrum of bone and soft tissue abnormalities termed renal osteodystrophy. Clinically most important manifestation of renal bone disease includes secondary hyperparathyroidism, osteomalacia/rickets, osteoporosis, adynamic bone disease and soft tissue calcification. As a complication of long-term hemodialysis and renal transplantation amyloid deposition, destructive spondyloarthropathy, osteonecrosis, and musculoskeletal infections may occur. Due to more sophisticated diagnostic methods and more efficient treatment classical radiographic features of secondary hyperparathyroidism and osteomalacia/rickets are now less frequently seen. Radiological investigations play an important role in early diagnosis and follow-up of the renal bone disease. Although numerous new imaging modalities have been introduced in clinical practice (scintigraphy, CT, MRI, quantitative imaging), plain film radiography, especially fine quality hand radiograph, still represents most widely used examination.

A new serum assay to measure N-terminal fragment of telopeptide of type I collagen in patients with renal osteodystrophy

BACKGROUND: Up until now, there was little known about the use of bone resorption markers in the assessment of bone status in patients with chronic renal failure (CRF). The present study evaluated the ability of a new immunoassay for N-terminal telopeptide of type I collagen to assess bone turnover in a group of hemodialyzed patients. METHODS: The following parameters were measured in a fasting blood sample from 111 patients on maintenance hemodialysis for at least 2 years and in 120 healthy subjects: calcium, phosphorus, magnesium, BALP, PTH, and N-terminal telopeptide of type I collagen (NTx-ELISA, OSTEOMARK NTx Siero-Ostex International). RESULTS: Serum PTH, BALP, and NTx were significantly higher (P<0.001) in hemodialyzed (HD) patients than in healthy subjects. In HD patients, PTH was correlated to BALP and NTx (r=0.40 and 0.55, respectively). When combining PTH and BALP serum levels, 17 patients showed high turnover (HT) and 65 were found to have a normal to low turnover (N-LT). In HT patients, serum NTx and dialytic age were significantly (P<0.01) higher than in N-LT patients. Moreover, even after adjusting for age, body mass index, dialytic age, and calcium-vitamin D treatment, serum NTx discriminated between HT and N-LT with a sensitivity of 97.6% and a specificity of 90.9%. CONCLUSION: Although bone biopsy remains the reference method for the diagnosis of renal osteodystrophy, the combined use of markers of bone resorption and bone formation could improve the clinical management of renal bone diseases.