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Leg Clots May Not Travel to Lungs

TUESDAY, Oct. 20 (HealthDay News) -- New research raises doubts about the long-held medical dogma that dangerous blood clots in the lungs, known as pulmonary emboli, originate from clots in the deep veins of the legs or other parts of the lower body, which then break up and travel up through the body.

A study appearing in the October issue of the Archives of Surgery found that 85 percent of trauma patients with pulmonary emboli showed no sign of deep vein thrombosis, or blood clots in the lower extremities.

The lead author of the study, Dr. George Velmahos, chief of the division of trauma, emergency surgery and surgical critical care at Massachusetts General Hospital and professor of surgery at Harvard Medical School in Boston, said the findings also cast doubt on the use of filters to prevent the clots from traveling.

But an outside expert said the findings need to be received cautiously, at least for now.

"I think it's an interesting report. I wouldn't call it a bombshell", said Dr. Jack Ansell, chairman of the department of medicine at Lenox Hill Hospital in New York City. "I think this study by no means answers this question or reverses the original concept that most pulmonary embolisms originate as venous thrombosis [blood clots] in the deep veins of leg or sometimes in pelvis or abdomen."

According to Velmahos, the concept of clots in the lungs originating as clots in the legs has never been challenged, despite evidence in the literature that some patients suffering from pulmonary embolism did not show signs of having had a blood clot in the lower extremities.

For this study, Velmahos and co-authors looked back over medical records of 247 trauma patients who had undergone CT pulmonary angiography and CT venography.

Among 46 patients with PE, only 7 also had DVT, or 15 percent.

There are possible explanations, the team said. It's possible that the entire original clot detached itself, leaving no traces. However, cadaver studies suggest that only a part of the leg clot breaks away, and a remnant is typically left behind.

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