The prevalence of RVO may be as high as 0.5% in middle-aged adults and 4.6% in patients over 80 years old, suggesting several million adults are affected by this disease each year. “There is an uptick from imaging,” said Dr Shatzel. “I think some of these things are being increasingly recognized because patients are getting a lot more imaging, [allowing] asymptomatic detection.”

Little is known about the pathogenesis of RVO, and, to date, anticoagulation has not been shown to be effective. The review found no data to support the use of anticoagulation, antiplatelet agents, or thrombolytic agents in treating patients with RVO. The authors suggested modification of risk factors and use of local therapies for managing patients with RVO.

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A Concern About Overtesting

Dr Shatzel said he routinely sees excessive use of genetic panels, which are expensive but rarely enlighten clinicians. “They cause patients a lot of psychological worry, and I don’t find a lot of value in getting them. They are overused.”

There also appears to be a significant problem with inappropriate use of anticoagulation, born from a lack of clinical evidence. “Some patients can safely stop their use and the providers miss that opportunity,” Dr Shatzel noted. Some professional organizations have made suggestions for regulation of anticoagulation use, but there is significant room for improvement.

Hematologist Rachel Rosovsky, MD, of the Massachusetts General Hospital Cancer Center in Boston, noted that reviews like the one conducted by Dr Shatzel and colleagues can be helpful when there is a dearth of randomized trials to guide management strategies. “It is a good review,” Dr Rosovsky said in an interview with Hematology Advisor. “The authors do a nice job of highlighting each unusual site of clots and ways to think about them.”

She also emphasized the importance of remembering common thrombotic risk factors in addition to the more obscure risk factors for clots, noting that when a clot is identified in a patient of childbearing age, the patient should be asked about oral contraception use and should take a pregnancy test. “I also ask about the use of over-the-counter supplements, hormones (especially testosterone), or steroids, as these agents may be overlooked when trying to identify an underlying etiology,” noted Dr Rosovsky.

She said there is little published literature on clots in rare sites, and most studies do not involve randomized, controlled trials. “These sites are uncommon. The legs and the lungs are more common. As such, we often don’t have [enough patients] for investigators to do large trials to look at whether one treatment or management strategy is better than another,” said Dr Rosovsky.


1. Shatzel JJ, O’Donnell M, Olson SR, et al. Venous thrombosis in unusual sites: a practical review for the hematologist [published online September 28, 2018]. doi: 10.1111/ejh.13177