Uptake of bone imaging agents by diffuse pulmonary metastatic calcification

Fatal Generalized Metastatic Calcifications

Metastatic calcifications are a rare but potentially fatal complication of primary hyperparathyroidism (PHPT). In this case, a 76-year-old man with a previously asymptomatic PHPT developed a hypercalcemic crisis with severe pancreatitis following elective urologic surgery. Despite initial treatment focused on pancreatitis and subsequent organ failure, hypercalcemia persisted, leading to rapid progressive metastatic calcifications in multiple organs. Parathyroidectomy during ongoing pancreatitis successfully reduced calcium levels but not the calcifications. After 4 months of complications and persistent pain, the patient declined further treatment and ultimately succumbed to the disease. The current literature primarily reports single-organ metastatic calcifications due to PHPT. This case represents the only lethal case of systemic metastatic calcifications in the current century. Physicians should be aware of the potential deterioration of hypercalcemia following elective surgery, particularly in the context of renal impairment. Rapid correction of calcium levels may prevent severe complications such as fatal metastatic calcifications.

Unilateral metastatic pulmonary calcification in context of ipsilateral central pulmonary embolism

We report a case of unilateral left metastatic pulmonary calcification (MPC) in a 30-year-old woman with systemic lupus erythematosus, acute nephritis, and left main pulmonary artery pulmonary embolism. Unilateral MPC is rare and is mostly seen in the context of ipsilateral pulmonary embolism. The proposed mechanism is the promotion of calcium salts precipitation by focal alkalosis resulting from reduced blood flow to the lung affected by the pulmonary arterial obstruction.

Extraosseous distribution of 99mTc-diphosphonates during bone scintigraphy: review of the literature with case series presentation

PURPOSE

Technetium-99m (99mTc)-diphosphonates represent the most common radiopharmaceutical used for bone scintigraphy. Even if the uptake in bone tissue has been widely explored, atypical uptake could be seen in soft tissue malignancies during bone scintigraphy. Increased vascularization and endothelium permeability represent front-row players in the biodistribution of the tracer, albeit other causes have been identified such as trauma, necrosis, the presence of calcification in metastasis, the pH of the tissue and consequently the type of ion concentration.

CONCLUSION

The aim of this paper is to summarize the state of art of atypical soft tissue uptake seen in cancer tissues. The research was conducted on PubMed. The analysis of the literature suggests that calcium metabolism and ionic saturation have a pivotal role in the biodistribution of bone tracers. This phenomenon ranks in a complex scenario that includes carcinogenesis and cancer environment aspects. We also report two cases in our Institution in which atypical uptake in cancer tissues was observed.

Nuclear medicine imaging findings in end-stage renal disease and renal transplant complications

The aim of this review is to discuss end-stage renal disease (ESRD) and renal transplant complications and present the nuclear medicine imaging findings. The conditions discussed are renal osteodystrophy, metastatic calcification, and renal transplant complications, such as vascular occlusion and acute tubular necrosis. A total of eight nuclear medicine imaging scintigraphy primarily of bone and renal scintigraphy were selected and the imaging features of the complications are discussed. This article highlights the role of nuclear medicine imaging in diagnosis, quantitative and qualitative assessment of renal function, and monitoring of complications associated with ESRD and renal transplant.

Metastatic microcalcification in the lungs and stomach due to hyperparathyroidism: A case report

We present a case of a 34-year-old man who was admitted to our hospital with a six-month history of nausea and vomiting that had worsened over the past two weeks. Diagnosis of primary hyperparathyroidism (PHPT) due to a single parathyroid adenoma was confirmed by laboratory results and imaging but following pharmacological therapy the patient developed a dry cough. Single-photon emission tomography/computed tomography (SPECT/CT) with technetium-99m-diphosphonate (^99mTc-MDP) was used to assist in the diagnosis and results showed diffuse metastatic microcalcification in the lungs and stomach. The patient underwent right parathyroidectomy and ^99mTc-MDP SPECT/CT scan six months later showed a significantly reduced radioactive distribution in the lungs and none in the stomach. Diffuse metastatic microcalcification in the lungs and stomach due to PHTP is rare and can easily be misdiagnosed.

A Reversible Gastric Uptake of Bone Scintigraphy in a Patient with Hypercalcemia

Hypercalcemia is a severe complication in cases of vitamin D intoxication that can result in metastatic calcification. We herein report a female case with hypercalcemia due to eldecalcitol administration associated with the increased uptake of technetium-99m hydroxymethylene diphosphonate (^99mTc-HMDP) as the bone-scanning agent in the stomach. A histologic assessment using biopsy specimens identified metastatic calcification of the stomach. After the normalization of serum calcium levels, the gastric uptake of ^99mTc-HMDP disappeared. This case indicates the usefulness of bone scintigraphy with ^99mTc-HMDP to detect visceral metastatic calcification and to monitor its therapeutic effects in patients with hypercalcemia.

Pulmonary Calcifications: Is it an Entity in the New World Dialysis Patient?

Metastatic pulmonary calcification (MPC) has been described in the literature to affect up to 60% of dialysis patients. Several case series of MPC were described in 1960s and 1970s. Patients are generally asymptomatic or may present with acute respiratory distress. This entity is associated with up to 60% mortality. We hereby report a case of chronic kidney disease on maintenance hemodialysis who presented with unexplained recurrent dyspnea despite adequate hemodialysis. She was evaluated and found to have a rare presentation of calciphylaxis.

Metastatic pulmonary calcification: high-resolution computed tomography findings in 23 cases

Objective

The aim of this study was to evaluate the high-resolution computed tomography (HRCT) findings in patients diagnosed with metastatic pulmonary calcification (MPC).

Materials and Methods

We retrospectively reviewed the HRCT findings from 23 cases of MPC [14 men, 9 women; mean age, 54.3 (range, 26-89) years]. The patients were examined between 2000 and 2014 in nine tertiary hospitals in Brazil, Chile, and Canada. Diagnoses were established by histopathologic study in 18 patients and clinical-radiological correlation in 5 patients. Two chest radiologists analyzed the images and reached decisions by consensus.

Results

The predominant HRCT findings were centrilobular ground-glass nodules (n = 14; 60.9%), consolidation with high attenuation (n = 10; 43.5%), small dense nodules (n = 9; 39.1%), peripheral reticular opacities associated with small calcified nodules (n = 5; 21.7%), and ground-glass opacities without centrilobular ground-glass nodular opacity (n = 5; 21.7%). Vascular calcification within the chest wall was found in four cases and pleural effusion was observed in five cases. The abnormalities were bilateral in 21 cases.

Conclusion

MPC manifested with three main patterns on HRCT, most commonly centrilobular ground-glass nodules, often containing calcifications, followed by dense consolidation and small solid nodules, most of which were calcified. We also described another pattern of peripheral reticular opacities associated with small calcified nodules. These findings should suggest the diagnosis of MPC in the setting of hypercalcemia.

Unusual visceral distribution of technetium-99m-methylene diphosphonate in a case of hypercalcemia of malignancy

We report a case of 18-year-old boy who presented with vomiting, backache, and fever for 1-month, diagnosed to have anaplastic large cell lymphoma of urinary bladder with hypercalcemia and metastatic calcification in multiple viscera. His computed tomography scan was suggestive of soft tissue lesion in the urinary bladder and multiple lytic skeletal lesions. Bone scan showed unusual visceral uptake in lungs, liver, spleen, and myocardium in addition to osseous lesions. The clinical laboratory test revealed functional impairment of visceral organs. The patient died 3 months later.

Pulmonary calcification in renal failure patient incidentally revealed by bone scintigraphy

Pulmonary calcification is a subdiagnosed metabolic lung disease that is commonly asymptomatic and frequently associated with end-stage renal disease. We report a case of a 21-year-old man with a 4-year history of end-stage renal disease without respiratory symptoms. We discover incidentally on a bone scan a pulmonary calcification. Parathyroidectomy was refused by the patient. After 3 months of medical treatment, a second bone scan was done, and we found a partial response.

Metastatic pulmonary calcification: state-of-the-art review focused on imaging findings

Metastatic pulmonary calcification (MPC) is a subdiagnosed metabolic lung disease that is commonly associated with end-stage renal disease. This interstitial process is characterized by the deposition of calcium salts predominantly in the alveolar epithelial basement membranes. MPC is seen at autopsy in 60-75% of patients with renal failure. It is often asymptomatic, but can potentially progress to respiratory failure. Chest radiographs are frequently normal or demonstrate confluent or patchy airspace opacities. Three patterns visible on high-resolution computed tomography have been described: multiple diffuse calcified nodules, diffuse or patchy areas of ground-glass opacity or consolidation, and confluent high-attenuation parenchymal consolidation. The relative stability of these pulmonary infiltrates, in contrast to infectious processes, and their resistance to treatment, in the clinical context of hypercalcemia, are of diagnostic value. Scintigraphy with bone-seeking radionuclides may demonstrate increased radioactive isotope uptake. The resolution of pulmonary calcification in chronic renal failure may occur after parathyroidectomy, renal transplantation, or dialysis. Thus, the early diagnosis of MPC is beneficial. The aim of this review is to describe the main clinical, pathological, and imaging aspects of MPC.

Abnormal extraosseous activity in both lungs and stomach in pre-transplant 99mTc-MDP bone scan disappearing after renal transplant

A chronic kidney disease male patient presenting with bone pains, fever, weakness, and clinically ascites was subjected to four technetium-99m-methylene diphosphonate (Tc99m-MDP) bone scans, two before renal transplant and two after renal transplants. Pretransplant bone scan revealed metabolic bone disease with focal insufficiency fractures. Marked extraosseous activity in both lungs and stomach was also visualized. On regular hemodialysis (HD) after 4 months, repeat pretransplant bone scan showed persistent uptake in lungs and stomach, representing altered calcium metabolism with microcalcifications. He underwent human leukocyte antigen (HLA) matched live donor renal transplantation, started on immune-suppression and steroids. Posttransplant bone scan at 20 days revealed no definite interval change, but bone scan performed approximately 17 months posttransplant showed resolving metabolic bone disease and the tracer uptake in the lungs and stomach was no more visualized. Patient clinically followed-up until the date (February 2013) is asymptomatic with serum creatinine of 1.5 mg/dl, no bone scan done.

[Pulmonary metastatic calcification]

INTRODUCTION

The lung is the organ most frequently involved by metastatic calcification. This condition is probably under-diagnosed, the patients usually being asymptomatic. This article summarizes the current knowledge concerning pulmonary metastatic calcification.

BACKGROUND

The pathogenesis of pulmonary metastatic calcification is not well known, but it involves phosphate-calcium balance, renal function and pH. The most frequently encountered aetiologies are hyperparathyroidism, neoplastic bony lesions, and renal failure. The definitive diagnosis is achieved by histology, radiological examinations being insensitive. The clinical manifestations are various and can include a pulmonary restrictive syndrome, diffusion abnormalities, hypoxaemia and respiratory failure. The latter can be severe and influence the prognosis adversely: 19 cases of fatal pulmonary metastatic calcification have been reported. The treatment is aetiological and symptomatic.

VIEWPOINT

The prognostic factors for a poor outcome of this potentially lethal condition remain to be determined. The management of asymptomatic patients is also uncertain.

CONCLUSIONS

Pulmonary metastatic calcification is a rare condition of complex pathogenesis. The clinical manifestations are varied, ranging from asymptomatic to severe, even fatal.

Bone scintigraphy in the diagnosis of skeletal involvement and metastatic calcification in multiple myeloma

The contribution of bone scintigraphy to the diagnosis of skeletal involvement in multiple myeloma was evaluated in a consecutive, unselected series of 25 previously untreated patients. Definite scintigraphic abnormalities were found in 11 patients (localized in 4, generalized in 7) (44%). In the majority of patients the clinical value of the information gained from scintigraphy was roughly equal to that found by radiography. However, 2 patients with normal and 2 with questionable bone scans had X-ray evidence of skeletal involvement, and the extent of bone destruction in 4 cases was seriously underestimated in the bone scans. Small osteolytic lesions were as a rule not detected by scintigraphy. On the other hand, in 8 patients the bone scan added information of involvement of ribs, pelvis and vertebrae, not clearly visualized by X-ray. In 2 patients, both with IgA myeloma, hypercalcemia and uremia, a massive extraskeletal uptake of the bone-seeking isotope was observed. Autopsy verified in one case the presence of a disseminated metastatic calcification.

Calcium deposition with or without bone formation in the lung

Pulmonary calcification and ossification occurs with a number of systemic and pulmonary conditions. Specific symptoms are often lacking, but calcification may be a marker of disease severity and its chronicity. Pathophysiologic states predisposing to pulmonary calcification and ossification include hypercalcemia, a local alkaline environment, and previous lung injury. Factors such as enhanced alkaline phosphatase activity, active angiogenesis, and mitogenic effects of growth factors may also contribute. The clinical classification of pulmonary calcification includes both metastatic calcification, in which calcium deposits in previously normal lung or dystrophic calcification, which occurs in previously injured lung. Pulmonary ossification can be idiopathic or can result from a variety of underlying pulmonary, cardiac, or extracardiopulmonary disorders. The diagnosis of pulmonary calcification and ossification requires various imaging techniques, including chest radiography, computed tomographic scanning, and bone scintigraphy. Interpretation of the presence of and the specific pattern of calcification or ossification may obviate the need for invasive biopsy. In this review, specific conditions causing pulmonary calcification or ossification that may impact diagnostic and treatment decisions are highlighted. These include metastatic calcification caused by chronic renal failure and orthotopic liver transplantation, dystrophic calcification caused by granulomatous disorders, DNA viruses, parasitic infections, pulmonary amyloidosis, vascular calcification, the idiopathic disorder pulmonary alveolar microlithiasis, and various forms of pulmonary ossification.

Soft tissue uptake of Tc99m-MDP in acute lymphoblastic leukemia

Acute lymphoblastic leukemia (ALL) is associated rarely with hypercalcemia. This may be due to elevated levels of parathyroid hormone-related peptide (PTHrP). We report a case of an 18-year-old female patient who was presented with a pathological fracture of left intertrochanteric region. Bone scintigraphy was consistent with features of hypercalcemia associated with metastatic calcification. A bone marrow biopsy led to the diagnosis of ALL. The mechanism of hypercalcemia in ALL, metastatic calcification and soft tissue uptake of bone seeking agents in this case are discussed in detail.

Diffuse, intense lung uptake on a bone scan: a case report

PURPOSE

Clinical and scintigraphic findings are described in a patient with unexpected diffuse lung uptake on bone scan after a heroin overdose.

METHODS

The patient's Tc-99m MDP bone scan is reviewed along with the pertinent clinical history and laboratory findings.

RESULTS

Marked diffuse and symmetric lung uptake is present on bone scintigraphy in a patient with a history of acute renal failure and a markedly elevated calcium-phosphate product but normal renal function and laboratory values at the time of the examination.

CONCLUSIONS

The incidental observation of metastatic calcification by bone scintigraphy is important, because it may aid in the diagnosis of a previously unsuggested elevated calcium-phosphate product, renal failure, or both. Furthermore, the intensity of tracer localization on bone tracer-specific imaging may help evaluate the activity of the metastatic calcification process.

The role of bone scanning in the detection of metastatic calcification: a case report

Metastatic calcification associated with renal failure is well described. Bone scanning agents accumulate to various degrees within extraskeletal sites of metastatic calcification. The authors describe a patient with polycystic kidney disease resulting in renal failure, with the subsequent development of secondary hyperparathyroidism and metastatic calcification. Bone scintigraphy revealed abnormal uptake in both lungs, the right leg, and the right hand.

Thoracic complications in uremic patients and in patients undergoing dialytic treatment: state of the art

No organ in the chest is spared the negative effects of uremia. The dialytic treatment itself is often associated with a large array of thoracic complications. We review the main thoracic manifestations of the terminal uremia from the radiological point of view, such as: uremic pleuritis and pericarditis, uremic pneumonia, renal osteodystrophy, infections, and metastatic pulmonary calcifications. Respiratory function derangement and the problems related to peritoneal dialysis and hemodialysis are discussed in some detail, along with the diagnostic role of plain films, US, nuclear medicine, and CT. The main focus of this review is on the hydration problems and pulmonary edema, often related to a large number of pathogenetic factors. Based on our experience, we think that the chest X-ray is not able to accurately discriminate between cardiogenic edema and fluid overload edema (so-called renal pulmonary edema). The radiological findings of the thoracic complications in uremic patients are multiple and complex but, in most cases, the imaging techniques may offer an accurate and noninvasive diagnostic approach, with a high benefit-cost ratio.

MR appearance of pulmonary metastatic calcification

We report a case of metastatic pulmonary calcification that showed hyperintense signal on T1-weighted MRI. This uncommon MR appearance of calcification is similar to the MR characteristics of calcification in the brain due to abnormal calcium metabolism.

Metastatic pulmonary calcification mimicking air-space disease. Technetium-99m-MDP SPECT imaging

Metastatic pulmonary calcification (MPC), a complication of chronic renal failure, is uncommonly diagnosed antemortem, yet may be a significant etiology of pulmonary dysfunction in patients with renal failure. The degree of respiratory distress often does not correlate with the degree of macroscopic calcification. Patients with extensive calcification may be asymptomatic, while others with subtle calcification or normal chest radiographs may have severe respiratory compromise. Additionally, the findings on chest radiographs may be confused with air-space disease, including pulmonary edema and pneumonia. Radionuclide imaging may detect MPC in the setting of normal chest radiographs, and confirm the diagnosis when there are radiographic findings of air-space disease without macroscopic calcification. We present a patient with bilateral upper lobe disease suspected to represent edema or pneumonia, proven to represent MPC on 99mTc MDP scintigraphy with single photon emission computed tomography (SPECT), CT, and later at transbronchial biopsy.

Pulmonary alveolar microlithiasis in a Saudi child and two cousins

Pulmonary alveolar microlithiasis is a rare disease and only 32 cases have been reported in children under 12 years of age. The first report on Saudi children with this disorder and on affected cousins is presented, supporting the possible hypothesis of it being an autosomal recessive disorder. The importance of differentiating it from other conditions, particularly pulmonary tuberculosis, and the current approach to diagnosis and management are discussed.

Localised pulmonary metastatic calcification associated with pulmonary artery obstruction

BACKGROUND

Metastatic pulmonary calcification, a complication of uraemia and disordered calcium metabolism, may be diffuse or localised. The factors that determine calcium precipitation are complex, but tissue alkalosis is thought to be important. As obstruction of the pulmonary artery theoretically causes local alkalosis a retrospective necropsy study was carried out to examine the relation between metastatic pulmonary calcification and vascular obstruction.

METHODS

Five patients with focal and two with diffuse metastatic calcification in the lungs were identified over eight years. Lungs were studied macroscopically and by light microscopy, haematoxylin and eosin and histochemical stains being used for calcium.

RESULTS

Underlying risk factors for calcification in these patients included renal failure in six and disseminated malignancy in five. In the five patients with localised calcification obstruction of the pulmonary artery by thrombus or tumour was found proximal or adjacent to areas of calcium deposition. In two patients metastatic calcification was confined to a lung with unilateral pulmonary artery thromboembolic occlusion. Calcification was not specifically associated with infarction, pneumonia, or diffuse alveolar damage. Lesions of the pulmonary artery were not seen in the two patients with diffuse bilateral metastatic calcification.

CONCLUSION

In this small series there was a spatial association between pulmonary artery obstruction and localised metastatic calcification. It is proposed that pulmonary artery obstruction alters the microchemical environment of the lung, favouring tissue alkalosis and thereby enhancing parenchymal calcification in patients predisposed to this condition.

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.

Accumulation of technetium-99m MDP in pseudomyxoma peritonei

An ovarian mucinous cystadenocarcinoma which moderately accumulated Tc-99m MDP was imaged during a whole body bone scan. The primary tumor and its implants in the peritoneal cavity were both visualized and correlated with US and TCT scan findings. As a result, the radiopharmaceutical distribution accurately delineated the primary tumor and the region of tumor involvement within the peritoneal cavity. Therefore, a whole body bone scan offers a potential method for assessing neoplastic size and spread.

Unusual site of extraosseous uptake of Tc 99m-HMDP due to subcutaneous heparin injections. Report of two cases

The soft tissue uptake of 99mTc-hydroxymethylene diphosphonate (99mTc-HMDP) due to subcutaneous injections of heparin calcium is reported in two patients with osteosarcoma. This uptake occurs in an unusual site, i.e. the shoulders and the anterior and posterior compartments of the upper arms.

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.

Bone scintigraphy in the diagnosis of pulmonary calcification in multiple myeloma

We present a case of multiple myeloma in which pulmonary calcification was clinically shown by bone scintigraphy and subsequently confirmed at autopsy. It is suggested that, in patients with myeloma, radionuclide bone scanning may be of value for differentiating deposits in the lung due to calcification from those due to other types of pulmonary infiltration revealed by chest X-rays. A thorough review of the relevant literature is presented.

Diffuse pulmonary uptake of 99mTc bone-imaging agents: case report and survey

Over the past 5 years, we have encountered 6 cases of diffuse pulmonary uptake of 99m-Tc bone-scanning agents (incidence, 0.04%). To assess the significance of this phenomenon, we reviewed all of the cases reported since 1974 (Including our series, a total of 32 cases). Three groups can be discerned, the first consisting of 24 patients without radiological calcifications in the lungs and with hypercalcemia of different origins (mostly hyperparathyroidism). Of the eight autopsies performed in this group, seven revealed extensive calcifications in alveolar walls and lung vessels; the other autopsy showed no calcification at all and only bronchopneumonic lesions. The second group consists of 6 patients in chronic dialysis. The last group consists of 2 patients having diffuse pulmonary alveolar microlithiasis with extensive radiologic calcifications. The mechanism of lung uptake of 99m-Tc bone-imaging agents is probably the same as that of bone uptake (chemisorption on hydroxyapatite crystals), although other uptake mechanisms have also been discussed. Bone scintigraphy can be useful in the detection of early pulmonary calcifications, which have been associated with impaired pulmonary function and, due to their size, are generally not detected by X-ray.

Uptake of 99mTc-MDP by pseudomyxoma peritonei: a case report

A patient with pseudomyxoma peritonei secondary to a mucin-secreting adenocarcinoma demonstrated striking, diffuse uptake of 99mTc-MDP throughout the abdomen. The radiopharmaceutical distribution accurately delineated the region of tumor involvement within the peritoneal cavity.

Massive pulmonary calcification in two infants with congenital cardiac lesions

Two infants with congenital heart disease and radiographically demonstrated pulmonary calcification are described. One infant also suffered from idiopathic hypercalcaemia and subcutaneous fat necrosis. Diffuse radiographic pulmonary calcification in infants has not been reported previously. The possible aetiology is discussed.

Pulmonary calcification in hemodialyzed patients detected by technetium-99m diphosphonate scanning

Metastatic pulmonary calcification, a well-known complication in patients with chronic disease, has been demonstrated postmortem in patients with a negative chest X-ray. Recently, scintigrams with bone-seeking radionuclides have been used to detect such subclinical pulmonary calcium deposits. We describe 23 patients on maintenance hemodialysis with no evidence of pulmonary calcification on chest X-ray who were prospectively studied by lung scanning with a bone-seeking radionuclide and pulmonary function testing. Of the 23 patients, 14 (61%) had a positive technetium-99m diphosphonate (99mTc-DP) scan (group 1). These patients were on dialysis 38 +/- 5 months compared with 12 +/- 4 months in 9 patients with a negative scan (group 2) (P less than 0.01). Age, sex, blood pressure, hematocrit, serum calcium, phosphorous, bicarbonate, magnesium, and calcium X phosphorus product, as well as parathyroid hormone level did not differ between the two groups. Of 10 group-1 patients tested, 7 had abnormal pulmonary diffusion capacity compared with non in 5 group-2 patients tested (P = 0.014). Histologic examination of the lung in 1 group-1 patients who expired revealed calcification (amorphous on X-ray diffraction), whereas none was found in 1 group-2 patients autopsied. These observations suggest that in patients on maintenance hemodialysis, pulmonary scanning with 99mTc-DP is a sensitive method for detecting pulmonary metastatic calcification, which may be associated with an abnormality in pulmonary diffusion capacity.