Scintigraphic skeletal changes in uremic patients on regular hemodialysis

Usefulness of bone uptake ratio of bone scintigraphy in hemodialysis patients

OBJECTIVE

It is important to estimate the bone metabolism in patients with renal osteodystrophy. The methods of estimation must be noninvasive, accurate, and able to measure repeatedly.

METHODS

The regions of interest on bone scintigraphy were drawn over the radius in 22 hemodialysis patients (10 males, 12 females). The bone/soft tissue ratio (B/ST ratio) was calculated for all patients. The bone soft tissue ratio of both skull (S) and radius (R) was obtained from the resultant count ratios. We investigated the correlation between intact parathyroid hormone (PTH), alkaline phosphatase (ALP) and the uptake ratios S and R.

RESULTS

Intact PTH had a significantly linear correlation with R (r = 0.745, p < 0.0001) and S (r = 0.702, p = 0.0001). ALP also had a significantly linear correlation with R (r = 0.537, p = 0.009) and S (r = 0.772, p < 0.0001).

CONCLUSION

The measurement of the bone soft tissue ratio of radius on bone scintigraphy was crucial for estimating renal osteodystrophy.

A clinical assessment of the relationship between bone scintigraphy and serum biochemical markers in hemodialysis patients

BACKGROUND

Renal osteodystrophy is a metabolic bone disease and a common complication of end-stage chronic renal failure and maintenance dialysis treatment. In this study, we examined the correlation between quantifying bone scintigraphy and serum biochemical markers in hemodialysis patients.

METHODS

Bone scintigraphy with technetium-99m-hydroxy-methylene-diphosphonate (99mTc-HMDP) was performed on 28 patients on maintenance hemodialysis. Bone scintigraphy was performed using a standard protocol and was quantified by setting regions of interest (ROIs) over selected regions. The bone-to-soft-tissue ratio (B/ST ratio) at each region was calculated in all patients. The B/ST ratios were then compared with serum biochemical markers.

RESULTS

The B/ST ratio for the skull correlated well with serum bone-specific alkaline phosphatase (BAP) (r = 0.735, p < 0.001), serum deoxypyridinoline (DPD) (r = 0.806, p < 0.001) and intact parathyroid hormone (intact PTH) (r = 0.701, p < 0.001). The B/ST ratio for the lumbar spine correlated with intact PTH (r = 0.387, p < 0.05) but not with serum BAP or serum DPD. The B/ST ratio for the femoral neck correlated with serum DPD (r = 0.431, p < 0.05) and intact PTH (r = 0.449, p < 0.05) but not with serum BAP.

CONCLUSIONS

Our data suggest that quantitative bone scintigraphy is a sensitive and useful method for evaluating bone metabolism in hemodialysis patients. The B/ST ratio for the skull may reflect changes of bone metabolism in hemodialysis patients.

A Comparison of Bone Scans in Uremic Patients Treated with Intermittent Peritoneal Dialysis Or Hemodialysis

The aim of the study was a comparative analysis of bone scans in uremic patients treated with intermittent peritoneal dialysis (IPD) or hemodialysis (HD). Bone scintigraphy was performed using technetium Tc 99m etidronate (EHDP) in 28 uremics (age 46.0±13.5 years, x±SD) on IPD for 3.1±3.0 months and 28 uremics (age 43.5±11.6 years) on HD for 47.3±33.9 months. Serum c terminal parathormone (cPTH) exceeded 5.3±3.3 and 6.8±3.5 times the upper normal limit of 1.4 ng/mL in IPD and HD patients, respectively. Despite significant differences in dialysis treatment duration in IPD and HD patients, an increased Tc 99m EHDP uptake in bones was shown with similar frequency, when all the groups were compared. However, in the group of patients with serum cPTH exceeding four times the upper normal limit (n = 30) or in the age group less than 45 years old (n = 26), a greater marker uptake was observed in HD patients. Significant differences (p < 0.05) were shown in the cranial vault: 33% of HD patients (n = 18) with higher cPTH and 47% of those less than 45 years old (n = 15) revealed an increased marker uptake, whereas it was not observed in any IPD patient. When scans of HD patients dialyzed less than (n = 11) and more than (n = 17) 30 months were compared, a significantly higher appearance of increased marker uptake was shown in cranial vault (41% vs 0%, p < 0.02) and in sacral bone (82% vs 36%, p < 0.02) in patients with longer dialysis. The latter group of HD patients also showed an increased marker uptake in cranial vault compared to the entire group of PD patients (41% vs 7%, p < 0.01). Our studies suggest that bone scan changes, indicating secondary hyperparathyroidism, progress significantly with prolongation of dialysis treatment, especially in patients with higher cPTH levels of younger age.

Scintigraphy in the clinical evaluation of disorders of mineral and skeletal metabolism in renal failure

In patients with renal bone disease skeletal and extra-skeletal abnormalities can be visualised using conventional bone scintigraphy. Some of these abnormalities are associated with characteristic scintigraphic appearances, which are reviewed in detail, and the possible mechanisms involved are discussed. Specific imaging with iodine 123 serum amyloid P component and iodine 131 beta 2-microglobulin is also discussed in the diagnosis of beta 2-microglobulin amyloidosis specific to patients on dialysis. In the light of available evidence, it appears that bone scintigraphy plays, so far, a limited role in the clinical evaluation of skeletal and extra-skeletal abnormalities in chronic renal failure. The potential role of bone scintigraphy in identifying patients with aluminium-related bone disease needs to be investigated further, and in this respect special attention must be given to the problem of high soft-tissue activity associated with impaired renal function. Timing haemodialysis sessions before scintigraphic imaging deserves wider recognition as it reduces high soft-tissue activity, thereby allowing bone uptake to be assessed more accurately. Specific imaging of amyloidosis resulting from beta 2-microglobulin deposition is a promising technique, but the relative value of the two proposed radiopharmaceuticals needs further clarification.

Amyloid syndromes associated with hemodialysis

A historical review and current clinical findings relating a new type of amyloid material to long term hemodialysis are presented, followed by a review of the biochemistry, metabolism and involvement of beta 2-M and theories for the pathogenesis of HRA. The syndromes develop several years after replacement of renal function by dialysis, and seem to be progressive over time. Preliminary clinical studies utilizing more permeable artificial kidney membranes suggest their potential usefulness in the prevention of HRA syndromes, specifically those attributable to persistent elevation of serum beta 2-M; however, caution in their employment is advised. The development of effective treatment for long-term hemodialysis patients afflicted with CTS, arthritic symptoms and skeletal manifestations of HRA is unfortunately constrained by deficiencies in our knowledge. Renal transplantation has been demonstrated to reduce the elevated serum beta 2-M levels in hemodialysis patients to normal; however, the effectiveness of this modality to treat clinical manifestations of HRA has not been reported. Thus, efficacious treatment strategies have lagged considerable behind diagnostic techniques. Intensive research is needed as the story of this new form of renal osteodystrophy unfolds.

Bone scanning and photon absorptiometry in metabolic bone disease

Bone scan imaging with the current bone-seeking radiopharmaceuticals, the technetium-99m labelled diphosphonates, provides a functional display of skeletal metabolism and has dramatically improved our ability to investigate skeletal pathology. While the role of bone scanning in metastatic disease was recognized early, and welcomed by oncologists and other specialists alike, in the field of metabolic bone disease the realization of its potential value has been slower, with perhaps more reluctant acceptance. Nevertheless, the skeleton remains an extremely difficult organ to investigate, and a familiarity with bone scanning should be an essential part of the investigational armamentarium for anyone with an interest in the metabolic bone disorders. The measurement of bone mineral by photon absorptiometry is a relatively new technique, which is rapidly gaining acceptance. The ability to accurately detect and quantify changes in bone mass is potentially of considerable value in the diagnosis and management of osteoporosis. The technique provides us with an extremely important and powerful research tool but, at the present time, its role in clinical practice has yet to be established.

Radionuclide imaging in metabolic and systemic skeletal diseases

Radionuclide imaging with Tc-99m diphosphonates is not an effective method for detecting or ruling out most osteoporotic diseases including senile osteoporosis or accelerated postmenopausal osteoporosis, and the slow loss of bone tissue generally remains undetected by this modality. Nonetheless, it frequently surpasses or supplements radiographic findings in evaluating the focal complications of metabolic bone disease, including fractures, microfractures, stress fractures, vertebral compressions, Milkman-Looser zones, aseptic necrosis, and acute infarction. In contrast to its secondary role in osteoporosis, bone imaging is of prime importance in investigating hypercalcemia, because the major cause of this abnormality is skeletal metastatic malignancy. In defective bone mineralization due to hyperparathyroidism or osteomalacia, a general increase in diphosphonate skeletal uptake is detected more frequently than radiographic abnormalities. However, normal skeletal images do not rule out metabolic bone disease. Biochemical testing is more reliable in detecting primary hyperparathyroidism. On the other hand, in renal osteodystrophy, biochemical abnormalities are variable and bone imaging is helpful in assessing the severity of skeletal involvement, but not its etiology. Many methods of quantitating the kinetics of Tc-99m diphosphonates have been explored, such as plasma clearance, bone-to-soft-tissue ratios, 24-hour total body retention and 24-hour urinary excretion. None of these have been widely accepted. The value of bone imaging is established in other systemic diseases, most notably in Paget's disease, hypertrophic pulmonary osteoarthropathy, sickle cell disease, fibrous dysplasia, and sympathetic dystrophy.

Generalized soft tissue calcification in children and adolescents with end stage renal failure

Sixteen children and adolescents undergoing regular haemodialysis treatment were studied for the occurrence of metastatic calcifications. By the use of diphosphonate bone-scanning, roentgenography of the chest and skull and ocular slit lamp examination, generalized visceral calcification was diagnosed in two patients. No relationship between visceral calcification and biochemical, radiological or histological abnormalities of renal osteodystrophy was found. Our study demonstrates that visceral calcification also occurs in children with chronic renal failure and may be detected by scintigraphy.

Value of the 99mTc-methylene diphosphonate bone scan in renal osteodystrophy

The value of radionuclide bone scanning in the diagnosis of renal osteodystrophy is still debated. In order to re-examine this issue, 25 uremic patients treated by intermittent hemodialysis underwent 99m-Technetium Methylene Diphosphonate (99mTc-MDP) bone scan. They were subdivided into three groups according to quantitative bone histology. Group 1 (N = 8) had pure dialysis osteomalacia, group 2 (N = 7) mixed lesions, and group 3 (N = 10) pure osteitis fibrosa. The scintigraphic studies were interpreted by means of a five point semi-quantitative scale. Using this quantification, all but one group 1 patients had decreased bone tracer uptake, and all patients of group 3 had an increased uptake (chi square test of Yates, P less than 0.001). Among patients of group 2, bone uptake was decreased in the three patients with clearly reduced mineralization front and moderate osteitis fibrosa, but it was increased in all patients with severe osteitis fibrosa and subnormal mineralization front. A quantitative analysis of regional tracer uptake into bone was performed in two patients: one of group 2 and one of group 3. The results obtained clearly corroborated the semi-quantitative findings. Thus, in hemodialysis patients with symptomatic bone disease, the 99mTc-MDP bone scan provides useful information for the differential diagnosis between dialysis-related osteomalacia and secondary hyperparathyroidism. In patients with mixed lesions, the importance of bone tracer uptake appears to depend on the extent of the mineralization front and on the intensity of osteitis fibrosa.

Observations on computerized quantitative bone scintigraphy in renal osteodystrophy

Skeletal radiotracer (99mTc-HEDP) uptake was quantitated with and without the aid of a computer in 30 chronic dialysis patients with histologic evidence of renal osteodystrophy. Before scintigraphy, elevated soft-tissue activity due to the absence of renal radiotracer excretion was reduced by hemodialysis. The results were compared with those of a normal group and with the results of the biochemical and the bone morphometric studies of these patients. In all patients the radiotracer uptake was elevated, often markedly. In several patients with minimal histologic bone disease, however, soft-tissue activity could not be normalized by hemodialysis although its influence on the quantitative data could be further reduced (but not excluded) by computer evaluation of skeletal radiotracer uptake. Since the latter technique clearly distinguished the majority of the patients from the normals, it appears that computerized quantitative skeletal analysis is a potentially accurate scintigraphic method for detecting renal osteodystrophy. The significant relationship between skeletal radiotracer uptake, in particular at the bone biopsy site, and only the histologic features of increased bone turnover suggest that hyperparathyroidism is the major cause of this increased tracer uptake in renal osteodystrophy.

Osteosclerosis of the femoral head in long-term uraemic rabbits

The morphology of the femoral head of rabbits was studied by histomorphometric analysis of undecalcified sections after four and eight months' duration of surgically induced chronic renal failure. A significant increase in trabecular bone mas and osteoid tissue was found in the uraemic rabbits. Signs of osteonecrosis or increase bone resorption were not seen. 99mTechnetium-methylenediphosphonate osteoscintigrams showed increased uptake in the axial skeleton and all periarticular regions in uraemic rabbits. The serum concentrations of calcium and phosphate in the uraemic rabbits were increased.

Increased bone radiotracer uptake in renal osteodystrophy. Clinical evidence of hyperparathyroidism as the major cause

Bone radiotracer uptake in renal osteodystrophy was investigated in 35 dialysis patients by correlating the results of quantitative bone scintigraphy with those of biochemical and bone morphometric studies. There were highly significant correlations (P less than 0.001) between the total skeletal activity and the biochemical (iPTH and alkaline phosphatase), and histologic parameters of hyperparathyroidism. These clinical results strongly suggest that increased bone turnover i.e. hyperparathyroidism, rather than osteomalacia is the major cause of increased skeletal uptake in renal osteodystrophy.

A comparison of bone scanning and radiology in the evaluation of patients with metabolic bone disease

Bone scans and radiographs were evaluated in 80 patients with metabolic bone disease (27 with osteoporosis, 14 with primary hyperparathyroidism, 24 with renal osteodystrophy and 15 with osteomalacia). The bone scan did not suggest a metabolic bone disorder in any of 27 patients with histologically proven osteoporosis. In 22 (81%) patients radiographs were reported as showing osteoporosis. In 10 (70%) vertebral fractures were seen on X-ray while these were noted in 11 (41%) patients on the bone scan. Vertebral fractures were usually visualised on the bone scan when these had occurred less than one year previously. In primary hyperparathyroidism the bone scan was suggestive of a metabolic bone disorder in 7 of 14 (50%) patients, while radiographs were reported as showing evidence of hyperparathyroidism in three (21%) cases. The bone scan suggested the presence of a metabolic bone disorder in all 24 patients with renal osteodystrophy and 15 patients with osteomalacia while the correct diagnosis was obtained in 14 (58%) and nine (60%) of these patients on X-ray. It is concluded that the bone scan is the more sensitive investigation in patients with osteomalacia, primary hyperparathyroidism and renal osteodystrophy. For osteoporosis radiology is the investigation of choice but the bone scan may be of value in assessing the duration of vertebral collapse.

Semi-quantitative interpretation of the bone scan in metabolic bone disease: definition and validation of the metabolic index

Certain easily recognisable features are commonly seen in the bone scans of patients with metabolic bone disorders. Seven such features have been numerically graded by three independent observers in the scans of 100 patients with metabolic bone disease and of 50 control subjects. The total score for each patient is defined as the metabolic index. The mean metabolic index for each group of patients with metabolic bone disease is significantly greater than that for the control group (P less than 0.001).

Joint effusions after kidney transplantation

Thirty-seven consecutive renal transplant recipients were studied prospectively for joint disease. Six developed arthralgias while corticosteroid doses were being lowered. Eleven patients (30%) developed knee effusions at a mean interval of 10 days following transplantation. Synovial fluids were colorless or very pale yellow, with few leukocytes (mean, 28/mm3). These benign transudative effusions did not correlate with immunologic abnormalities, transplant rejection, crystal deposition, or avascular necrosis and may have been due to high dose oral corticosteroid therapy.