Benefits and limitations of Compression Ultrasonography
Contrast venography is the standard medical procedure used for the diagnosis of deep vein thrombosis. Limited use of this method is due to the invasive nature of the test and the side effects associated with the use of contrast material. Technological advancements have lead to the development of non-invasive tests. Impedance plethysmography was the first well evaluated non-invasive method that could overcome the limitation of invasive methods. Although this method had high accuracy for proximal vein thrombosis in symptomatic patients, but it was less sensitive for thrombi confined to the calf veins. So this method had to be conducted more than once to detect proximally extending thrombi in the calf vein. In early studies, this method was repeated five times over 2 weeks in patients who had an initially normal test result. At a later stage, the efficiency of the test procedure was further improved by reducing the repeat tests to two without compromising on the safety aspect.
Over the past decade, a new technology has emerged. Compression ultrasonography is a non-invasive method for the evaluation of patients with clinically suspected deep vein thrombosis. This is the method preferred because of its excellent accuracy for deep vein thrombosis and wide availability. Compression ultrasonography can be limited to a single spot in the groin and mid-popliteal fossa, where clear, distinct and reproducible images can be obtained. Similar to impedance plethysmography, this is not a suitable method for accurately evaluating the calf veins. As a result, serial compression ultrasonography testing remains necessary. Patients whose compression ultrasonography result is normal, needs to go for a repeat test. This limitation makes the diagnostic approach inconvenient for patients, labour intensive, and expensive. As a matter of fact, latest observations showed that some symptomatic patients with normal results on compression ultrasonography in the mid-popliteal fossa have thrombi confined to the more distal part of the popliteal vein.
We followed the simplified ultrasound strategy in patients with clinically suspected deep vein thrombosis. The anticoagulant treatment was conducted for patients who had normal results on compression ultrasonography on presentation and on a single repeat test 1 week later. They were assessed during follow up for 6 months.