Treatment duration for thrombosis of rare or unusual localization

Mark Crowther, MD, MSc, is a professor of medicine, chair of the Department of Medicine, and Leo Pharma Chair in Thromboembolism Research at McMaster University.

Are there any guidelines discussing the length of treatment in patients with thrombosis of rare or unusual localizations, such as the subclavian or visceral (portal) vein? When to stop treatment?

This is a very interesting question because these unusual site thromboses tend to be very rare and as a result, there’s relatively limited data.

My own personal practice is to say that if a person presents with an unusual site thrombosis, for example, an ovarian vein thrombosis, the first question is to look to see if there’s a cause. In many cases, there are. So, for example, in ovarian vein thrombosis, did it occur after delivery or in the setting of surgery? And if it did, I would treat that clot as I would treat any other secondary clot, that is, with 3 months of anticoagulant therapy.

If I can’t find a cause, then I would treat it more like an idiopathic or unprecipitated clot and usually treat those for extended durations. That is data that is carried over from leg deep vein thrombosis, but I think it’s reasonable here. And in the majority of cases of unusual site thrombosis you can identify a cause.

For example, one of the questions we had earlier, “Is thrombophilia testing indicated in patients presenting with clotting?” In general, the answer to that is not. But if you had a patient who presented with a splanchnic vein thrombosis, you might consider JAK2 testing. JAK2 is a permanent condition, which would then lead us to consider long-term therapy to prevent recurrent venous thromboembolism in that individual.