Characteristics

• Renal osteodystrophy is a global term used to describe bone and joint changes secondary to chronic renal failure.

• Osteomalacia is characterised by incomplete mineralisation of the normal bone tissue.

• Abnormal phosphate retention in renal osteodystrophy leads to hypocalcaemia with resulting secondary hyperparathyroidism.

• Combined features of osteomalacia and secondary hyperparathyroidism are seen.

Clinical features

• Osteomalacia tends to present with non-specific bone pain and muscle weakness. Fractures are common especially in the more severely affected patients. Typical sites include femoral neck, pubic rami and vertebral bodies.

• Renal osteodystrophy can also present with rather non-specific features. Weakness and bone pain are common. Fractures are the most frequent complication.

Radiological features

• Osteomalacia – osteopenia may be the only sign. Coarsened trabeculae with a decrease in number and size. Bone deformity from softening. Pseudofractures = Looser zones (lucent lines at right angles to bone margin, especially in the scapula and femoral neck) and overt fractures may be evident.

• Renal osteodystrophy is characterised by bony resorption, soft tissue calcification and osteopenia. Osteosclerosis of the vertebral endplates leads to the classical ‘rugger-jersey spine’. Pathological fractures can also occur through brown tumours and amyloid deposits. Sub-periosteal bone resorption should be sought in the distal phalangeal tufts and along the radial borders of the middle phalanges. Skull radiology may show a ‘salt and pepper’ appearance secondary to trabecular resorption.

• Bone scans are useful in showing ‘hot spots’ secondary to subtle fractures. Diffuse uptake (‘superscan’) is seen with renal osteodystrophy and can be confused with widespread metastatic disease.

Management

• Treatment is often directed towards the underlying cause of the disease.

• Medical management involves calcium and phosphate control.

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