A 56-year-old man noticed that his legs suddenly, and for no apparent reason, felt heavy, tired, and weak. Then they began to swell, worrying him enough to go to the emergency room for help.

The ER physician checked him over, learning that the man had neither chest pain nor shortness of breath - just those alarming leg problems. He had had an abdominal-wall hernia repaired a couple weeks before, but that had gone well, with no apparent complications.

His high blood pressure was well-controlled with medication, and a past deep-vein thrombosis (DVT) in the left leg had resolved after six months of treatment with blood thinner.

Ten years earlier, he had had gastric bypass surgery. Because he was at high risk for DVT, a retrievable vena cava filter was put in place as a precautionary measure. These devices are designed to capture an embolism, a blood clot that has broken loose from one of the deep veins in the legs on its way to the heart and lungs. They generally are used only as a temporary measure, but sometimes are left in place longer, as was the case with this patient.

The ER physician ordered a chest X-ray, which looked fine. Lab results included an elevated white blood cell count, suggesting inflammation or infection, and an abnormal creatinine value, indicating kidney failure.

The list of possible diseases causing his symptoms was long. A benign abscess or malignant tumor could be compressing his spinal cord. He might have Lyme disease. It might be an autoimmune disorder such as Guillain-Barré syndrome or multiple sclerosis.

Cardiovascular disorders including congestive heart failure and aortic occlusion are also part of this differential diagnosis.

Nothing could be ruled out just yet.

The solution appears on Page G7.

Joseph L. Grisafi, M.D., FACS, RPVI, is a vascular surgeon in East Norriton and Sellersville, and founder of the Artery & Vein Institute.