Anterior and posterior images.
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View second image(bs). Lateral skull scintigraphy.
View third image(xr). Lateral skull plain film
Full history/Diagnosis is available below
- Generalized diffuse increased uptake in all bones, with marked increased uptake in the calvarium.
- No focal increased uptake in the lower extremities to explain the patient's pain.
2. Skull plain films (image 3, same day as bone scintigraphy):
- Diffuse patchy, granular “salt and pepper” appearance of the calvarium.
Osteopenia is very common in patients with chronic renal failure and may be seen in either the high or low bone turnover forms of renal osteodystrophy. Glucocorticoid use by transplant patients contributes substantially to osteopenia.
Beta-2 microglobulin dialysis-related amyloidosis commonly occurs in patients on long-term dialysis (typically longer than 5 years). Carpal tunnel syndrome is usually the first manifestation. It is also characterized by arthralgias, bone cysts, pathological fractures and visceral involvement. Radiographically, juxta-articular lucent bone cysts may be seen.
In early stages of chronic renal failure, prior to bone disease, bone radiopharmaceutical uptake is normal but there is poor renal clearance and therefore soft tissue background will be increased at the normal imaging times. Secondary hyperparathyroidism occurs when there is sufficient loss of renal parenchyma that production of 1,25-dihydroxyvitamin D3 is reduced. This results in reduced intestinal calcium absorption and hypocalcemia. Decreased tubular excretion of phosphate leads to hyperphosphatemia. These changes result in increased parathyroid hormone (PTH) production. This secondary hyperparathyroidism causes osteitis fibrosa cystica, characterized by increased osteoclastic and osteoblastic activity with increased bone resorption and endosteal fibrosis.
“The clinical features of renal osteodystrophy include bone pain, skeletal deformity, growth retardation, fractures, extraskeletal calcifications, myopathy and pruritis” (Hruska, 1997). Bone painn generally occurs gradually and tends to be generalized. Severe bone pain is unusual and, when it occurs, is more typical of aluminum-overload osteomalacia. Bone deformity due to renal osteodystrophy is common, particularly in young children where the findings resemble rickets. A myopathy characterized by proximal muscle weakness may develop in renal osteodystrophy.
Extraskeletal calcification in end-stage renal disease may take the form of tumoral calcifications (peri-articular), medium-sized arterial calcification and visceral calcification (most commonly heart, lungs, kidneys, skeletal muscle and stomach). The propensity for calcification is related to a calcium/phosphate product greater than 75 (except for visceral calcification which seems to be unrelated), degree of hyperparathyroidism, serum magnesium levels, acidosis and local tissue injury.
Radiographic findings in renal osteodystrophy depend on the type of bone disorder and are not sensitive. In secondary hyperparathyroidism, subperiosteal resorption is the most sensitive finding but is only seen in under 50% of patients with histological evidence of resorption. Brown tumors may be seen in secondary hyperparathyroidism, but are less common than in the primary form.
Bone density measurements are frequently obtained in patients with renal osteodystrophy. The measurements are compromised by the presence of woven bone which contributes to the measured bone mineral density, but not to structural integrity.
Treatment of renal osteodystrophy consists of reducing phosphate levels with phosphate binders (such as calcium carbonate), careful control of dialysate calcium levels, correciton of acidosis and administration of vitamin D analogue supplements (especially calcitriol). In a small number of cases, these measures are unsuccessful due to persistent elevated PTH that occurs after chronic overstimulation of the parathyroid glands (tertiary hyperparathyroidism). In these cases, a partial or total parathyroidectomy may be undertaken. Another option is to perform a total parathyroidectomy with transplantation of some parathryoid tissue to the patient’s forearm (where further resection can more easily be undertaken if necessary).
The marked increased uptake in the calvarium and mandible, as seen in this case, is characteristic of hyperparathyroidism, renal osteodystrophy and anemia. Hyperparathyroidism and renal osteodystrophy may also cause periarticular increased uptake (faintly seen in this case), brown tumors (which may manifest as foci of either increased or decreased uptake), tie sternum, prominant costochondral junctions (also seen with osteomalacia and rickets - the “rachitic rosary”), prominantnt medial clavicles and soft tissue uptake in the lungs and stomach.
The skull plain film in this case reveals the “"salt and pepper"” appearance characteristic of renal osteodystrophy. In cases of severe anemias, a “hair on end” appearance may be seen in the calvarium.m.
This patient has a history of chronic renal failure with renal transplant 4 years ago. The imaging findings are most characteristic of renal osteodystrophy.
References and General Discussion of Bone Scintigraphy (Anatomic field:Skeletal System, Category:Metabolic, endocrine, toxic)
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