Duplex Scan in Patients With Clinical Suspicion of Deep Venous Thrombosis

Aguinaldo de Oliveira; Graciliano J. França; Enrique A. Vidal; Paulo S.D.B. Stalke; Liz A.V. Baroncini

Disclosures

Cardiovasc Ultrasound 

In This Article

Discussion and Conclusion

Discussion

In a systematic review,[2] the incidence of DVT in the entire general population is approximately 5 per 10000 per year of which 2 per 10000 are idiopathic. An additional 1-2 per 10000 have a new DVT combined with pulmonary embolism. In pregnant women the incidence of venous thrombosis is 1 in 1000 - 20000 pregnancies.[3] Fast and accurate diagnosis of DVT allows for immediate treatment and improves clinical outcome. Chronic complications include recurrent thrombosis, post-thrombotic syndrome and chronic pulmonary hypertension.[4,5,6] In addition, in a recent cohort analysis of 4890 patients Huerta et al[7] found that an episode of venous thromboembolism is associated with a slight increased risk of myocardial infarction and increased risk of overall deaths during the first year after a venous thromboembolism episode. The modalities to diagnose DVT have improved substantially over the past decade. However, since DVT cannot be diagnosed solely by history and physical examination and requires specialist investigation, the role of duplex scan is crucial. Duplex scan can correctly diagnose deep and superficial venous thrombosis and can also precisely identify other pathologies such as Baker's cyst, haematoma, extrinsic compression and edema. In addition, with increasing frequency, physicians are requesting duplex scan to detect lower extremity DVT in the event of suspected pulmonary embolism, even in the absence of leg symptoms. In a study to determine the incidence of DVT in a high-risk group of ICU patients receiving DVT prophylaxis, a duplex scan was performed in 102 subjects.[8] Twelve patients receiving DVT prophylaxis were documented to have DVT by venous duplex scans. In patients without signs or symptoms of DVT, only two (3.6%) presented abnormal scans. The authors recommended that venous scans be performed only in patients with features suggestive of DVT or pulmonary embolism. In the present study, all patients presented symptoms. In addition, the symptoms due to other pathologies were very similar to DVT. These factors make the duplex scan very important in differential diagnoses. Duplex scanning has improved in precision and has gained popularity. It is safer than other invasive techniques, such as contrast venography, and also provides a more timely diagnosis and in a more efficient manner than most noninvasive techniques.[9] In a prospective, double-blind study, Killewich et al[10] found a sensitivity and specificity for duplex scanning relative to contrast venography of 85-95%. For deep venous thrombosis below the knee, Miller et al[11] found a sensitivity and specificity for duplex scanning relative to contrast venography of 85.2%-99.2%. In the present study we did not perform contrast venography after the duplex scan. The referring physician's decision to continue the investigation or not was based on the duplex scan results. However, as previously mentioned, in our environment the physicians only request the scan in the case of suspicion of DVT. Currently, it is not common to request a contrast venography after a duplex scan. Consequently, the definitions of sensitivity, specificity, accuracy, and negative and positive predictive values are not adequate in this study. As a non-invasive technique, it is the method of choice for high-risk patients. For example, in haemodialysis patients, with haemostatic disorders, duplex scanning could be performed safely.[12] In cancer patients, duplex scanning is the method of choice for the diagnosis of central venous catheter-related upper extremity deep venous thrombosis in symptomatic patients and for screening of asymptomatic thrombosis in this specific population.[13] However, some issues should be considered. In early and asymptomatic DVT, diagnosis by duplex scanning shows a decrease in accuracy. This is due to the fact that the fresh thrombus is not occlusive, has the same echogenicity as blood, and has a reduced consistency, therefore jeopardizing the compressibility test, the most sensitive test for DVT.[1] In these cases, duplex scanning should be performed 2-3 days later to confirm or exclude the diagnosis. In addition, the sensitivity and specificity of duplex scanning in vessels below the knee is not good. However, with improvements in echo machines and with meticulous technique, duplex scanning is highly accurate in diagnosing acute symptomatic deep vein thrombosis in lower extremities, thus invasive techniques are avoided in over 90% of the cases, even at the tibioperoneal level. There are no guidelines regarding the diagnosis of DVT, however some algorithms are adopted. In these algorithms, the duplex scan should initially be performed to accurately exclude or confirm DVT.[4] In the present study the duplex scan was the first method of choice for the referring physician to either confirm or exclude DVT and look for other pathologies. It is a convenient, safe and quick exam and most physicians prefer it to other methods when faced with patients presenting leg swelling.

Conclusion

Deep venous and superficial venous thromboses were diagnosed in 49% of the cases. In 30.9% of the cases, the duplex scan presented other pathologies.

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