eMedicine Specialties > Radiology > Musculoskeletal

Hyperparathyroidism, Secondary: Imaging

Author: Ali Nawaz Khan, MBBS, FRCS, FRCP, FRCR, LRCP, Chairman of Medical Imaging, Professor of Radiology, NGHA, King Fahad National Guard Hospital, King Abdulaziz Medical City, Riyadh, Saudi Arabia
Coauthor(s): Farrah Jabeen, MB, BCh, MRCS, FRCR, House Officer, Radiology Training Program, North West Deanery, UK; Sumaira MacDonald, MBChB, PhD, MRCP, FRCR, Lecturer, Sheffield University Medical School; Endovascular Fellow, Sheffield Vascular Institute
Contributor Information and Disclosures

Updated: Nov 5, 2008

Radiography

Findings

In children, widening of the growth plates of the long bones may be present, with irregularity of the metaphyseal margins and disorganization of the growth plate, which is indicative of advanced rickets. These changes of gross disease have been likened to the rotting of a wooden post at its stem.

Severe osteopenia may be complicated by pathologic fractures. Epiphyseal displacement of metaphyseal fractures may be present; the most commonly involved sites include the distal radius, the proximal humerus, the distal femur, and the heads of metacarpal and metatarsal bones.⁶

Skeletal maturation may be retarded. Lateral Blount disease may occur as a result of lateral angulation of the proximal tibial epiphysis and genu valgum. Jaw enlargement has been described.

In adults, subperiosteal bone resorption characteristically affects the phalangeal tufts, the radial aspect of the proximal and middle phalanges of the fingers, the metatarsals, the rib margins, the lamina dura, and the medial margins of the proximal humerus, femur, and tibia.

Intracortical bone resorption, which results in a lacy appearance, involves the cortex of the metacarpals. Endosteal resorption may involve the phalanges of the digits. Subligamentous bone resorption affects the tuberosities of the humerus, the ischium, and the greater and lesser femoral trochanters, as well as the inferior surface of the lateral end of the clavicle and the inferior surface of the calcaneus. Subchondral resorption occurs at several sites, including the sternoclavicular and acromioclavicular joints, the symphysis pubis, the sacroiliac joints, and the discovertebral joints. An erosive-type arthropathy is reported with secondary hyperparathyroidism.

Brown tumors occur, but these are less common with secondary hyperparathyroidism than they are with primary hyperparathyroidism. However, as the life expectancy of patients with chronic renal disease has increased, brown tumors have increasingly been identified with renal osteodystrophy. Brown tumors may occur in the spine and form expansile masses, which can be complicated by paraplegia. Brown tumors of the sellar and/or parasellar regions and face may appear as destructive lesions.

The skull may show a granular pattern, which may be associated with thickening, particularly in the inner table. Osteomalacia may be predominant in patients with renal osteodystrophy. Associated Looser transformation zones and pathologic fractures, possibly symmetric, can be present. Osteosclerosis may affect the epiphyses, metaphyses, pelvis, and ribs. Frequently, a classic rugger-jersey spine is observed; it is caused by ill-defined bands of increased bone density adjacent to the vertebral endplates.

An organized periosteal reaction (eg, periosteal neostasis) may develop around the metatarsals, femora, and pelvis. This finding, although not typical, is more common in secondary hyperparathyroidism than it is in the primary form of disease. Generalized osteopenia, often severe, may occur. Digital phalangeal brachydactyly secondary to healed renal osteodystrophy may be present. Rarely, kyphoscoliosis may occur.

Extra-osseous calcification is more common in secondary hyperparathyroidism than it is in the primary form of the disease, and it is even more common in long-standing disease. Abnormal calcification and other abnormalities include the following:

• Tumoral calcification associated with bone erosions
• Chondrocalcinosis
• Vascular calcification
• Calcified pulmonary nodules
• Cerebral subcortical calcification
• Calcification within the eyes
• Layering of soft-tissue calcification
• Cardiac calcifications
• Breast calcifications
• Renal calcification
• Hepatic calcification

Degree of Confidence

In renal osteodystrophy, bone resorption is invariably present. Correlation of findings with the patient's history and biochemical parameters should lead to the correct diagnosis. However, secondary hyperparathyroidism associated with osteomalacia of dietary origin may cause vague symptoms and, sometimes, nonspecific biochemical findings.

False Positives/Negatives

The radiologic features of secondary hyperparathyroidism are similar to those of the disease's primary form. The radiologic changes can sometimes mimic those observed in Paget disease.

Computed Tomography

Findings

CT scan findings in renal osteodystrophy include abnormal sacroiliac joints, multiple brown tumors, osteitis fibrosa cystica, prominent Schmorl nodes, periarticular tumoral calcifications, and slipped capital femoral epiphyses.⁷ Layering of soft-tissue calcification is well demonstrated on CT scans. In general, however, and in comparison with other modalities, CT scanning offers no advantage in the diagnosis of secondary hyperparathyroidism.

Degree of Confidence

CT scanning is rarely employed in screening exams for renal osteodystrophy.⁷ Nonetheless, knowledge of the CT scan appearances of secondary hyperparathyroidism is important; it helps clinicians avoid confusing the changes associated with secondary hyperparathyroidism with those resulting from other pathologic conditions. On the whole, however, CT scanning is not sensitive in the detection of changes related to secondary hyperparathyroidism.

False Positives/Negatives

Soft-tissue calcification is not specific to secondary hyperparathyroidism and has myriad causes. Erosive changes attributable to secondary hyperparathyroidism may easily be confused with changes in rheumatoid arthritis, seronegative spondyloarthropathies, infection, or even malignancy. Brown tumors and amyloid deposition can easily be mistaken for a neoplastic process.

Magnetic Resonance Imaging

Findings

MRI can adequately reveal skeletal deformity, cortical thickening, and irregular trabecular patterns in children with renal osteodystrophy.^7,8 In addition, MRI shows osteonecrosis and intraosseous soft-tissue masses more conspicuously than do plain radiographs. This modality also shows diffuse, nonspecific marrow changes.⁹  One case describes the MRI diagnosis of thoracic myelopathy caused by spinal stenosis secondary to renal osteodystrophy.¹⁰ MRI is also useful in the detection of parathyroid hyperplasia.

Degree of Confidence

Based on current experience, MRI findings in secondary hyperparathyroidism are not specific enough for this modality to replace radiography. Also, MRI has low sensitivity and specificity in the detection of parathyroid hyperplasia.

False Positives/Negatives

MRI findings in chronic osteodystrophy can often mimic those of other diseases.

Ultrasonography

Findings

Ultrasonography is useful in the detection of parathyroid enlargement.^11,12

Degree of Confidence

The sensitivity of ultrasonography in the detection of parathyroid hyperplasia is low. Imaging modalities in secondary hyperparathyroidism are of a limited value in guiding medical and surgical treatment. However, if percutaneous alcohol ablation is contemplated as an adjunct to medical treatment, ultrasonography may be useful in the initial localization of an abnormal gland.

False Positives/Negatives

Ultrasonography has a high rate of false-negative findings in the diagnosis of parathyroid hyperplasia. A thyroid tumor may mimic a parathyroid adenoma.

Nuclear Imaging

Findings

Superscan shows diffusely increased activity in the axial skeleton and perhaps in the calvaria and mandible. The ratio of bone to soft tissue is increased, and the kidneys and urinary bladder are absent.

[ CLOSE WINDOW ]

Superscan shows diffusely increased activity in the axial skeleton and perhaps in the calvaria and mandible. The ratio of bone to soft tissue is increased, and the kidneys and urinary bladder are absent.

Technetium-99m bone scan in a patient with chronic renal disease shows uptake in the lungs and calvaria. No renal or bladder activity was noted. (The kidneys are not shown.)

[ CLOSE WINDOW ]

Technetium-99m bone scan in a patient with chronic renal disease shows uptake in the lungs and calvaria. No renal or bladder activity was noted. (The kidneys are not shown.)

Several radionuclide features are reported in secondary hyperparathyroidism. A superscan may reveal the following findings:

• Diffusely increased activity in bones, specifically in the axial skeleton, calvaria, mandible, costochondral junctions, long bones, and sternum
• An increased bone-to–soft tissue ratio
• Absent kidney and urinary bladder findings

Technetium-99m sestamibi and subtraction scintigraphy with thallium-201 (²⁰¹ Tl) and^99m Tc have been used to localize parathyroid hyperplasia in secondary hyperparathyroidism, but they are of limited value.^{12,13,14,15,16}

Degree of Confidence

Radionuclide bone scans have low sensitivity and specificity in the detection of secondary hyperparathyroidism. The use of radionuclides in the diagnosis of parathyroid hyperplasia also has a limited role.

False Positives/Negatives

Besides renal osteodystrophy and/or hyperparathyroidism, the following conditions, displaying the same features as hyperparathyroidism, may appear to be present:

• Hyperthyroidism
• Extensive skeletal metastases
• Aplastic anemia
• Leukemia
• Widespread Paget disease
• Myelofibrosis and/or myelosclerosis
• Waldenström macroglobulinemia
• Systemic mastocytosis

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