CT or MRI scans will occasionally detect an incidental iliofemoral DVT, PE or intra-abdominal thrombosis (IVC, portal, splenic, mesenteric or renal vein). This is particularly common in cancer patients undergoing staging CT scans. When such an incidental, asymptomatic venous thromboembolism (VTE) is discovered, the question arises whether the patient should be treated with anticoagulants or not. Very little is known about the natural history such clots, few clinical studies exist. Therefore, no solid recommendations can be given.
How often are incidental VTEs found?
One study found that 2.6 % of patients undergoing CT of the chest for various reasons other than to rule in/out PE, had an incidental PE [ref 1]. These were mostly patients who were hospitalized or had cancer, i.e. those at higher risk for VTE. Another study found that 2.5 % of cancer patients who underwent staging CTs had a VTE; about half of these were iliofemoral DVTs or PEs, the other half consisted of DVTs in the abdomen (IVC, portal, mesenteric and renal veins) [ref 2].
Should patients with incidental clots be treated with anticoagulants?
No studies have been performed to investigate whether such patients benefit from anticoagulants or not. Therefore, no clear recommendations can be given. When finding an asymptomatic DVT, particularly in the thigh or the pelvis, or a PE, many physicians will probably put the patient on anticoagulants for some period of time (several months). This practice is supported by the ACCP guidelines discussed below [ref 4]. How to mange patients with other incidentally discovered clots is completely unclear due to the absence of natural history, outcome and anticoagulant treatment (yes/no) data.
What treatment guidelines exist?
The highly respected ACCP (American College of Chest Physician) guidelines recommend: “In patients who are unexpectedly found to have asymptomatic DVT of the leg or PE, we recommend the same initial and long-term anticoagulation as for comparable patients with symptomatic DVT” (Grade 1 C recommendation = strong recommendation, based on low or very low-quality clinical trial evidence). The ACCP guidelines do not take reference to how other incidentally discovered clots, such as in the abdomen (portal, mesenteric and renal veins), should be treated.
My personal approach
Decision making on anticoagulants yes/no for incidentally discovered VTE needs to take into consideration a patient’s risk factors for the previous as well as for future thrombotic events (immobility, surgery, cancer, etc) and risk factors for bleeding. Findings on imaging studies suggesting that the VTE is old may be one of the arguments against the use of anticoagulants. Weighing the risk/benefit, a very individualized decision needs to be made. If the patient has no significant risk factors for bleeding, I have a tendency to recommend anticoagulants for some period of time.
- Dentali F et al. Prevalence and clinical history of incidental, asymptomatic PE: A meta-analysis. Thromb Res 2010;125:518-522.
- Douma RA et al. Incidental VTE in cancer patients: prevalence and consequence. Thromb Res 2010;125:e306-e309.
- Dentali F et al. Prognostic relevance of asymptomatic venous thromboembolism in patients with cancer. J Thromb Haemost 2011;ePub.
- Kearon C et al. Antithrombotic therapy for venous thromboembolic disease. American College of Chest Physician Evidence-Based Clinical Pratice Guidelines. Chest 2008;133:454S-545S.
For Patients: this same information, written for patients, is available here.
Disclosure: I have no financial conflict of interest with the content of this post.
Last updated: April 22nd, 2011