Paediatric Imaging

Hyperparathyroidism, secondary

(also called renal osteodystrophy), metabolic disturbance usually seen in any patient with poorly controlled chronic renal insufficiency of any kind with diminished glomerular infiltration. The serum phosphate is high which depresses the serum calcium leading to lower levels of ionised calcium. As a result, the parathyroid glands become hyperplastic and excessive amounts of parathormone are secreted. Osteoclastic activity is increased and excessive resorption of calcium and phosphate from the bone occurs which result in radiological features due to subperiosteal bone resorption, cyst formation and variable diminished bone density.

The classic pathological lesion in renal osteodystrophy, osteitis fibrosa, is characterized by marrow fibrosis, increased production of bone and focal areas of resorption of bone. Osteosclerosis may occur; it is related to the affects of parathyroid hormone and may be due to stimulation of osteoblastic activity and increased production of trabecular bone. Soft tissue calcification is primarily the result of an increase in the calcium phosphate product in extracellular fluid.

In children subperiosteal bone resorption involves the femoral necks, the proximal humeri and the medial aspects of the proximal tibia. Subperiosteal resorption is mostly detected along the radial aspects of the middle and proximal phalanges of the second and third digits (Fig.1). Other sites include the ends of clavicles, superior aspects of ribs, symphysis pubis, sacroiliac joints and distal radius. The cortex and trabeculae are ill defined in contrast to the sharply defined thin cortex of osteopenia due to osteoporosis.

Diffuse osteosclerosis produces an overall increase in bone density and indistinct trabeculae. Involvement of the spine produces a "rugger jersey" appearance. Nearly 40% of children with end-stage renal disease have metaphyseal sclerosis.

Soft tissue calcification in subcutaneous, periarticular, vascular and visceral areas may develop. See renal osteodystrophy and hyperparathyroidism primary

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Fig.1

Frontal view of 3rd and 4th digits showing subperiosteal resorption of bone with cortical irregularity.
Hyperparathyroidism, secondary, Fig.1