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Bone Case 2 Answers

1) Is there any abnormal pattern of bone uptake?

There is a photopaenic defect in the region of the left femoral head with an area of raised uptake lateral to it. The photopaenic defect is in keeping with a hip prosthesis. Plain films of the region confirmed a previous hemiarthroplasty with heterotopic new bone formation, just lateral to the femoral head.

2) Describe the unusual appearances of the kidneys

The kidneys are unequal in size and show markedly raised uptake.

3) What can cause this?

The unequal size of kidneys has a wide differential diagnosis of acquired and congenital causes. In an elderly man, unequal kidney size is suspicious for renovascular disease, particularly in the clinical setting of treatment-resistant hypertension. The precise cause of the asymmetric kidneys in this patient is unknown.

The raised uptake in the substance of the kidney has a similarly wide differential diagnosis. Obviously, activity should be seen in osseous metastasis, but activity will also be seen in non-osseous metastatic disease. Adenocarcinomas such as prostate, colon, pancreas, and ovarian soft tissue metastasis are notable for having increased activity at metastatic sites. Some other primary non-osseous neoplasms that demonstrate increased activity include thyroid, lymphoma, lung, neuroblastoma, breast and haemangioma. Even without the presence of ectopic calcification, increased radiopharmaceutical activity can be visualized. This is thought to be due to the disruption of the cell membrane and loss of calcium-phosphate pump, and therefore deposition of cellular calcium into the cell. Considering this information, it is clear to see how other mechanisms can cause abnormal radiopharmaceutical activity, such as fat necrosis, hepatic necrosis, infarction or vascular insult, and radiation treatment ports.
Other entities that can cause soft tissue accumulation include: fluid collections (such as effusions & ascites), uraemia, sickle cell disease, rhabdomyolysis, amyloidosis, scleroderma, sarcoid, hyper/hypoparathyroidism, hyperthyroidism, chemotherapy toxicity and at soft tissue injection sites

In this gentleman, it was thought to be due to nephrotoxicity from platinum-based chemotherapy. Click here to see a companion case, also likely secondary to systemic chemotherapy for melanoma and nephrotoxicity.

Click here to see 2 different cases of raised soft tissue uptake in women with breast carcinoma, either due to primary disease, recurrence or after surgery.

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The text is entirely the opinion of the author and does not necessarily reflect that of RUH NHS Trust or the Bristol Radiology Training Scheme. Website content devised by Paul McCoubrie.