Role of lower extremity US in patients with clinically suspected pulmonary embolism

Ultrasound Evaluation of the Lower Extremity Veins

Over the past 2 decades venous ultrasonography has become the standard primary imaging technique for the initial evaluation of patients for whom there is clinical suspicion of deep venous thrombosis (DVT) of the lower extremity veins. This article addresses the role of duplex ultrasonography and color Doppler ultrasonography in today's clinical practice for the evaluation of patients suspected of harboring a thrombus in their lower extremity veins. It reviews the clinical presentation and differential diagnoses, technique, and diagnostic criteria for acute and chronic DVT. In addition, it addresses the sonographic evaluation of venous insufficiency.

MR angiography with sensitivity encoding (SENSE) for suspected pulmonary embolism: comparison with MDCT and ventilation-perfusion scintigraphy

OBJECTIVE

The aim of our study was to determine the utility of time-resolved contrast-enhanced MR angiography combined with sensitivity encoding (SENSE) for patients with pulmonary embolism. SUBJECTS AND METHODS. Forty-eight consecutive patients (26 men and 22 women; age range, 27-73 years; mean age, 55 years) with suspected pulmonary embolism underwent chest radiography, contrast-enhanced MDCT, MR angiography with SENSE, ventilation-perfusion scintigraphy, and pulmonary angiography. MR angiography with SENSE was performed using IV administration of gadolinium contrast medium with a 3D turbo field-echo pulse sequence (TR/TE, 4.0/1.2; flip angle, 30 degrees ) on a 1.5-T scanner. Capabilities of diagnosing pulmonary embolism using MR angiography (data set A), contrast-enhanced MDCT (data set B), contrast-enhanced MDCT with MR angiography (data set C), ventilation-perfusion scintigraphy (data set D), and contrast-enhanced MDCT with ventilation-perfusion scintigraphy (data set E) were determined by receiver operating characteristic analysis, using the results of pulmonary angiography as the reference standard. The diagnostic capability of each data set was analyzed on a per-vascular zone and a per-patient basis with the McNemar test.

RESULTS

Sensitivity and specificity of data set A were 83% and 97%, respectively, on a per-vascular zone basis and 92% and 94%, respectively, on a per-patient basis. Specificity and accuracy of data set A were significantly higher than those of data set D on a per-patient basis (p < 0.05).

CONCLUSION

Time-resolved MR angiography with SENSE is effective for the diagnosis of pulmonary embolism.

Pulmonary embolism: making sense of the diagnostic evaluation

Despite the publication of the Prospective Investigation of Pulmonary Embolism Diagnosis in 1990, the diagnostic evaluation of pulmonary embolism continues to be approached in an inconsistent fashion. The reasons for this are unclear but likely have to do with inadequate methods for predicting pretest probability of disease and the inconvenience and perceived risk of pulmonary angiography. Because pulmonary embolism and its treatment carry substantial risk of morbidity and mortality, a consistent approach to evaluation is desirable. This article reviews large, prospective studies that suggest that it may be unnecessary to diagnose pulmonary embolism with the certainty that pulmonary angiography allows. Finally, the article proposes an algorithm that may be acceptable to patients and clinicians alike if safety is confirmed in future prospective studies.

Physicians' attitudes toward misdiagnosis of pulmonary embolism: a utility analysis

RATIONALE AND OBJECTIVES

The purpose of this study was to measure physicians' utilities for outcomes after ventilation-perfusion lung scanning and to explore physicians' attitudes toward misdiagnosis and the treatment of patients suspected of having pulmonary embolism (PE) in a quantitative manner by using a utility analysis.

MATERIALS AND METHODS

Before ordering lung scanning for suspected PE, physicians rated five possible outcomes on a scale of 0-100 by using a computer order-entry system. These responses were rescaled and transformed to a utility measure by using the Torrance transformation.

RESULTS

The mean utility for the potential outcomes after 341 lung scans were (a) no PE and no treatment (true-negative, 93 +/- 22 [mean +/- standard deviation]), (b) PE with appropriate treatment (true-positive, 84 +/- 24), (c) no PE but patient received treatment (false-positive, 54 +/- 32), (d) PE but patient did not receive treatment (false-negative, 14 +/- 23), and (e) death during pulmonary angiography (2 +/- 11). After lung scanning for acute PE, physicians placed greatest value on excluding the diagnosis (true-negative). Providing unnecessary treatment (false-positive) was valued in the midrange of utilities. The value of missing PE (false-negative) was rated almost equal to that of dying during pulmonary angiography.

CONCLUSION

Physicians consider providing treatment for PE without objective confirmation of an embolus to be preferable to missing a case of PE.

Correlation of diagnostic imaging and subsequent autopsy findings in patients with pulmonary embolism

OBJECTIVE

We determined the frequency of correct antemortem diagnosis in patients who underwent lung scintigraphy for suspected pulmonary embolism and for whom the pulmonary embolism was proven at autopsy.

MATERIALS AND METHODS

We performed a longitudinal follow-up study of 1210 consecutive patients who underwent scintigraphic imaging for suspected pulmonary embolism. Patients for whom pulmonary embolism was proven at autopsy within 30 days of lung scintigraphy were studied. Diagnostic testing and risk factors were compared in patients with and without an antemortem diagnosis of pulmonary embolism.

RESULTS

The antemortem diagnosis was made in four of eight patients with autopsy-proven pulmonary embolism, yielding a sensitivity of 0.5 (95% confidence interval, 0.16-0.84). The diagnosis was made by high-probability lung scintigraphy in two patients, by pulmonary arteriography in one patient, and by lower extremity venous sonography in another patient. The imaging investigation for suspected pulmonary embolism included only lung scintigraphy in four patients in whom the antemortem diagnosis was incorrect: two with low-probability scintigraphy and two with intermediate-probability scintigraphy. Risk factors were similar for patients with and without pulmonary embolism.

CONCLUSION

In this cohort study of patients suspected of having pulmonary embolism, the antemortem diagnosis was not made in 50% of patients in whom pulmonary embolism was later proven at autopsy. Underuse of diagnostic testing may have been to blame. We therefore believe that further study is needed to help identify patients with suspected pulmonary embolism who may benefit from additional diagnostic testing after low- or intermediate-probability lung scintigraphy.

Work-up of patients with malignancy after an intermediate-probability ventilation-perfusion scan: why don't physicians pursue a definitive diagnosis?

RATIONALE AND OBJECTIVES

The authors determined whether there are specific patient characteristics associated with the clinical decision to eschew further diagnostic testing in patients in whom a ventilation-perfusion (V-P) scan indicates intermediate probability of pulmonary embolism (PE).

MATERIALS AND METHODS

The authors reviewed all intermediate-probability V-P scans obtained in a 12-month period. Patients were divided into two groups. Group 1 comprised patients in whom a definitive diagnosis of PE was not obtained and who were not treated for PE (n = 57); group 2 comprised patients in whom the diagnosis of PE was confirmed or excluded and who, if PE was confirmed, received appropriate treatment (n = 14). Age, gender, frequency of malignancy, and survival of patients in groups 1 and 2 were compared.

RESULTS

The frequency of malignancy was significantly greater in group 1 than in group 2 (P = .012). Although the estimated 2-year survival of group 1 patients was significantly less than that of group 2 patients (P = .039), this difference is likely due to confounding by age and malignancy.

CONCLUSION

When an intermediate-probability V-P scan is obtained, physicians are significantly less likely to pursue a definitive diagnosis of PE in patients with malignancy.

Controversies in the use of lower extremity sonography in the diagnosis of acute deep vein thrombosis and a proposal for a unified approach

During the past 10 years, lower extremity venous ultrasonography (LEUS) has essentially replaced contrast venography for the evaluation of patients suspected of acute thromboembolic disease. Along with this change in technology, the number of studies performed to rule out DVT has increased dramatically, and there has been controversy in the literature regarding the most appropriate role of LEUS. Specifically, four questions have been raised: (1) What is the appropriate role of LEUS in patients with a nondiagnostic V/Q scan?; (2) Is there a need to examine the contralateral (asymptomatic) leg of patients presenting with unilateral DVT symptomatology?; (3) What role, if any, does LEUS play in the evaluation of patients with bilateral leg symptoms?; and (4) When can a limited examination of the leg be performed? The purpose of this article is to provide a balanced review of these issues and to present an algorithm for a reasonable, integrated approach to the use of LEUS among patients suspected of having acute thromboembolic disease.

Role of venous duplex scanning in patients with suspected pulmonary embolism

PURPOSE

We examined the use of venous duplex scanning (VDS) in the diagnosis of pulmonary embolism (PE) at our institution.

METHODS

Patients undergoing lower extremity VDS from October 1988 through June 1995 were cross-referenced with those who underwent ventilation perfusion (V/Q) scans and pulmonary angiography (PA) for PE.

RESULTS

A total of 664 of 3534 VDS were for "rule out PE." Deep venous thrombosis was found in 13%. A total of 256 VDS were in conjunction with V/Q scans in 249 patients, with only 8% undergoing PA. Deep venous thrombosis was present in 18% for those with both V/Q and VDS compared with 10% (p < 0.01) for those with VDS as the sole study. The order in which V/Q, VDS, and PA were obtained and the relationship of positive studies was examined.

CONCLUSION

We found no pattern to the sequence of tests ordered. V/Q scan rather than VDS should be the first study in the evaluation of PE. PE was diagnosed or excluded in nearly one third of patients based on V/Q as the initial study. A total of 29% of VDS could have been avoided. Treatment could be determined on the basis of VDS as the initial study in only 13%. We found only 14% incidence of positive PA in patients with nondiagnostic V/Q scans. We advocate judicious use of diagnostic tests in a stepwise fashion to appropriately treat patients with suspected PE.