Doppler Ultrasound
In Work Up Of Patients With Suspected Pulmonary Thromboembolic
Disease Baptist Memorial Hospital - Experience

by Wes Brewer, M.D. and M. Moinuddin, M.D.

Doppler ultrasound (DU) is a frequently performed test in patients suspected of thromboembolic disease such as pulmonary embolism (PE) or deep vein thrombosis (DVT). Since femoral and popliteal veins are primarily or secondarily involved in the majority of patients with pulmonary emboli and DU is perceived to be a very accurate test for the detection of thrombosis in these vessels, this test is commonly used clinically. Some studies have shown that DU carries a sensitivity and specificity of 95-100%, when compared to contrast venography, which is accepted as a Gold Standard. To determine the sensitivity at the Baptist Memorial Hospitals (East and Central), the following study was performed.

Those patients who underwent pulmonary angiography at the BMHC and BMHE during the 18-24 month period were identified. The medical charts of these patients were reviewed and DU performed on these patients were noted. The results of these data are as follows:

The charts of 84 patients who underwent pulmonary angiograms were available: 84 (36 at BMHE in an 18-month period and 48 at BMHC in a 24-month period).

We were surprised to see only two patients' DU were positive for thrombi among 24 patients who had pulmonary angiogram documented pulmonary emboli. This number expressed in percentage amounts to 8.3%. The medical literature suggests that a high percentage (50-80%) of patients with pulmonary emboli have positive DU for thrombi. The local data is not consistent with this conclusion. The possible causes include different patient population, poor methodology, erroneous interpretation, faulty studies in literature, etc. None of these seems to be the case at the BMH systems. Therefore, while the exact reason is not known, it is very important to be aware of very low incidence of positive DU in patients with pulmonary emboli at BMH. For example, if a patient gets an intermediate probability lung scan with negative DU (a common scenario), the referring physician may be tempted not to use anticoagulants. Realizing that only 8.3% of patients who had pulmonary emboli had positive DU in the above study, the predictive value of a negative DU is so poor that important clinical decisions cannot be made on a negative DU. Hence, not using anticoagulants may be hazardous in these settings.

Conclusion
While a positive DU argues heavily in favor of use of anticoagulants, the predictive value of negative DU is very low at the BMH and should not be used as evidence in withholding anticoagulants.

Dr. Wes Brewer, the co-author of this study, is a rotating intern who spent one month of his elective rotation with Dr. M. Moinuddin as clinical research rotation. He was offered several research projects by Dr. Moinuddin and he selected the one that is presented here. He will be starting Radiology Residency at the University of Florida, Gainesville, July 1998.