Role of duplex scanning in the diagnosis of asymptomatic lower-extremity deep vein thrombosis
(Portuguese PDF version)

Mariangela Giannini,1 Hamilton Almeida Rollo,2 Francisco Humberto de Abreu Maffei3

1. Ph.D. Assistant professor, Vascular Surgery, Department of Surgery and Orthopedics, Faculdade de Medicina de Botucatu (FMB), Universidade Estadual Paulista (UNESP), Botucatu, SP, Brazil.
2. Ph.D. Assistant professor and head of Vascular Surgery, Department of Surgery and Orthopedics, FMB, UNESP, Botucatu, SP, Brazil.
3. Professor, Vascular Surgery, Department of Surgery and Orthopedics, FMB, UNESP, Botucatu, SP, Brazil.

 

Correspondence:
Mariangela Giannini
Departamento de Cirurgia e Ortopedia
Faculdade de Medicina de Botucatu - UNESP
CEP 18.618-970 - Botucatu, SP, Brazil
Phone:+55 (14) 3811.6269/3811.6092
Fax:+55 (14) 3815.7428
E-mail: marigiannini@uol.com.br

ABSTRACT

The diagnosis of symptomatic deep vein thrombosis is well established using duplex scanning, with a sensitivity of 100% and specificity of 98% for proximal deep vein thrombosis, and 94% sensitivity and 75% specificity for distal deep vein thrombosis. In the early and asymptomatic deep vein thrombosis, diagnosis by duplex scanning is not well established yet, which shows a decrease in the accuracy of this diagnostic method. This is because the fresh thrombus is not occlusive, has the same echogenicity as blood and a reduced consistency, jeopardizing the compressibility test, which is the most sensitive test for deep vein thrombosis. This article will review published articles, which evaluated the accuracy of the duplex scanning in the diagnosis of asymptomatic deep vein thrombosis.

Key-words: venous thrombosis, diagnosis, lower extremity; ultrasonography.

J Vasc Br 2005;4(3):290-6

The lower-extremity deep vein thrombosis (DVT) is a frequent disease, with estimated incidence of 0.6 cases per 1,000 inhabitants/year in our environment, 0.8 cases per 1,000 inhabitants/year in the USA and 0.9 cases per 1,000 inhabitants/year in Sweden.1 It is mainly a complication of other clinical or surgical diseases, which is a cause for concern, due to complications such as pulmonary embolism (PE), chronic venous insufficiency (CVI) and chronic pulmonary insufficiency, which cause high morbidity and mortality rates.

The lower-extremity DVT is divided into proximal and distal, according to its location. Proximal, when it affects the iliac and/or femoral and/or popliteal vein with or without thrombosis of the leg veins; distal, when it affects only the leg veins. This division is important, because the risk of PE as a consequence of proximal DVT is higher, as well as the severity of the CVI, whereas the DVT only of the leg veins presents less risk of these complications. Nevertheless, there is a risk of progression of the distal thrombosis to proximal segments of up to 20%, which makes the distal DVT diagnosis recommendable.2

One of the most problematic aspects of DVT is its diagnosis. The clinical diagnosis is not enough, once, in the initial stages of the disease, only 30 to 50% of cases present typical signs and symptoms, as shown in patients with DVT acquired in the postoperative period, diagnosed by the labeled fibrinogen and confirmed by phlebography.1,3,4 On the other hand, from 30% to 50% of patients with signs and symptoms of DVT do not present the disease when its presence is verified by phlebography, which is the standard diagnostic method.5-14

When present, the clinical status may consist of: edema, pain, erythema, dilatation of the superficial venous system, temperature increase, muscular tenderness painful in response to palpation, pain in the deep venous tract, and cyanosis.1

However, there are other diseases that have a relation to DVT, such as subcutaneous infections, muscle rupture, myositis, muscle fatigue, hematoma, and rupture of Baker's cyst.15

The non-invasive methods currently available, such as the ultrasound Doppler or continuous-wave Doppler, plethysmography or impedance rheography and thermography, are not totally reliable or present management difficulties in the daily clinical practice.9,12,16,17 The phlebography, despite being the best diagnostic method, is an invasive examination and contraindicated for patients who present allergic reaction to the contrast, renal alterations or during pregnancy, besides having a high cost.1

The development of the duplex scanning (DS), which associates the real-time ultrasound (US) image with the spectral analysis of the ultrasound and color Doppler, allows the visualization of vessels, thrombi, neighboring tissues, and the assessment of blood flow.1 Mattos et al.,18 assessing the DS for the diagnosis of the symptomatic vein thrombosis, found sensitivity of 100% and specificity of 98% in the proximal segment; and sensitivity of 94% and specificity of 75% in the distal segment. These results are better than other non-invasive methods.

Kearon et al.19 reported that the imaging US with compression technique of the venous segments in symptomatic patients for proximal DVT is accurate, with sensitivity of 95%, specificity of 96% and positive predictive value of 97%.

Forbes & Stevenson20 assessed 50 patients with DVT symptoms in leg veins using the color-flow DS and power Doppler in a prospective and blind study compared to phlebography. They obtained sensitivity of 100%, specificity of 79%, positive predictive value of 71%, negative predictive value of 100% and accuracy of 86%. These results show an improvement in the diagnostic accuracy of the DS for the distal DVT when the power Doppler is used.

Stevens et al.21 have recently assessed the reliability and safety of the complete examination with DS (assessment of all lower-extremity deep veins, from the ankle to the inguinal region) in 445 symptomatic patients for DVT (first episode). Among patients with negative DS for DVT, 375 were followed-up for 3 months and the occurrence of thromboembolic phenomena was verified during this period. Most patients (372 or 99.2%) did not present thromboembolism, which suggests that the DS is a reliable examination for diagnosing the symptomatic DVT.

In patients with recent and asymptomatic DVT, the PE maybe the first clinical manifestation of the venous thromboembolism. Therefore, it is important to have a more accurate non-invasive diagnostic method, which can be used in patients with risk of developing this disease. In this situation, the patient may be asymptomatic, but present clots that have more chances to become fragmented and cause PE, since they have a recent formation. The diagnosis for this disease, in the asymptomatic stage, is also important for studies that include epidemiology, assessment of the efficacy in the use of prophylaxis, new drugs for treatment or prophylaxis, and to select patients who, during the use of prophylaxis, need to change for the anticoagulant therapy, aiming at avoiding complications and the symptomatic DVT. This importance was verified by Thomasson et al.,22 who found that 85% of patients who presented DVT were asymptomatic in the assessment of 400 patients after total knee and hip arthroplasty.

Kearon,23 in a review article, observed that non-invasive methods have low accuracy for diagnosing the asymptomatic DVT.

The accuracy of the DS for diagnosing the asymptomatic DVT is lower compared to the symptomatic DVT, probably because the venous thrombus, when it is recently formed, may not be occlusive and have a reduced consistency, jeopardizing the compressibility test of the DS, which is the most sensitive for diagnosing the DVT. We may add the fact that the recent thrombus has the same echogenicity as blood, making its visualization difficult.

The aim of this article was to review the articles published about the diagnosis of the asymptomatic deep vein thrombosis using the B-mode ultrasound and the duplex scanning.

In 1989, Borris et al.24 published the first study with the real-time B-mode US, with compression of the venous segments for diagnosing the asymptomatic DVT, compared to the phlebography. They assessed 65 patients after the elective surgery of total hip prosthesis, and noticed that it was possible to perform the US in these patients, and that the US was less accurate in the diagnosis of the DVT than the bilateral ascending phlebography.

In 1990, Borris et al.25 performed another study with an improved ultrasonography device. In this study, they prospectively assessed the occurrence of asymptomatic DVT in 61 patients submitted to the elective total hip arthroplasty, using real-time B-mode US, with compression of the venous segments for diagnosing the DVT, compared to the phlebography. They found sensitivity of 71% and specificity of 94% for the whole lower limb, and 73% and 96% for proximal, respectively. They then suggested that the US could be used as screening for the asymptomatic DVT. However, other studies published in the early 1990's did not show good sensitivity of the US for diagnosing the asymptomatic DVT.18,26,27 Among them, we can point out the study by Agnelli et al.,26 who emphasized, based on their results, that the US was not a good screening method, due to the low sensitivity in asymptomatic patients.

In the study mentioned above, Agnelli et al.26 prospectively assessed the real-time B-mode US, with compression of the venous segments, comparing it with the phlebography. They obtained sensitivity of 57% and specificity of 99% for proximal DVT. When they assessed proximal and distal together, they obtained sensitivity of 25% and specificity of 99%. Based on these results, they concluded that, due to the high specificity, the phlebography would not be needed in positive cases.

In 1992, Davidson et al.27 compared the color-flow DS with phlebography in 319 patients, 10 days after they were submitted to knee or hip arthroplasty. The DS was bilateral, only assessing the proximal segment. This diagnostic method showed sensitivity of 38%, specificity of 92% and positive predictive value of 26%, which is little sensitive for diagnosing the proximal asymptomatic DVT.

Mattos et al.,18 in 1992, assessed two groups of patients: symptomatic (77 limbs) and asymptomatic with high risk of DVT, after knee and hip surgery (190 limbs) with color-flow DS, compared with phlebography. For symptomatic patients, sensitivity was 100% and specificity was 98% for proximal DVT; 94% and 75% for distal; and for the assessment of the whole limb, 100% and 73%, respectively. For asymptomatic patients, sensitivity was 67% and specificity was 100% for proximal DVT; 56% and 98% below the knee; and for the assessment of the whole limb, 55% and 98%, respectively, which shows that the sensitivity for asymptomatic patients significantly decreased.

In 1993, Nicolaides & Kalodiki28 reported that the use of color-flow DS could improve the diagnosis of the asymptomatic DVT, based on the fact that, for symptomatic patients and proximal DVT, sensitivity increased from 91% to 97%, and specificity from 98% to 99%. They suggested that more studies should be made to corroborate these results.

In 1994, Koopman et al.,29 in a review article, showed that the real-time B-mode US with compression of the venous segments in asymptomatic patients presented low sensitivity - 59% (43%-100%) - and specificity of 98% (91%-95%) for proximal DVT, thus being better than the impedance plethysmography. They concluded that, for asymptomatic patients, the real-time B-mode US was not sensitive enough.

In 1994, Jongbloets et al.,30 in a study with the real-time B-mode US with compression of the venous segments, reached the same conclusion as Agnelli et al.26 in 1992.

In 1995, Wells et al.31 published a review article with metanalysis of the studies that used the B-mode US, the duplex scanning and the color-flow Doppler, compared with phlebography in asymptomatic patients submitted to orthopedic surgeries. The authors verified that the US has a moderate sensitivity and moderate positive predictive value when used for screening, showing sensitivity of 62% and specificity of 97% for proximal DVT, and sensitivity of 47% for DVT only in the leg. Moreover, they called attention to the occurrence of technical limitations in these situations.

Agnelli et al.,32 in 1995, in an analysis of diagnostic methods for asymptomatic DVT, concluded that the non-invasive methods (B-mode US, fibrinogen, impedance plethysmography, the association of impedance with fibrinogen) are not accurate. Under this situation, it is necessary to perform the phlebography. They report, for impedance plethysmography, sensitivity of 20% or less in asymptomatic patients. The association of impedance with fibrinogen does not result in an increase in the diagnosis in relation to their individual use. The B-mode US presented sensitivity of approximately 50%, in a study using the adequate methodology.

Still in 1995, Crippa et al.33 assessed 68 asymptomatic patients submitted to the elective total hip arthroplasty, comparing the real-time US with compression with the phlebography and obtained sensitivity of 63% and specificity of 98% for proximal DVT. They also studied the D-dimer, fibrinogen and products of the fibrinogen degradation at the 10th postoperative day, which showed sensitivity of 100% and specificity of 58%. They concluded that these methods should select patients who must be submitted to the US.

In 1996, Magnusson et al.34 assessed 138 asymptomatic patients submitted to the total hip arthroplasty, comparing the color-flow DS with the phlebography and obtained sensitivity of 62.5% and specificity of 99.6% for proximal DVT; 53.6% and 58.1% for distal; and 58.1% and 98% for all segments, respectively. They concluded that sensitivity is low for screening of high risk patients.

In 1997, Haines & Bussey35 showed that, for asymptomatic patients, the sensitivity of diagnostic methods significantly reduced (US with compression, US Doppler, US duplex scanning, impedance plethysmography, labeled fibrinogen), with no major alterations in specificity. They concluded that, when individually used, any non-invasive method is sensitive enough to assess asymptomatic patients.

In 1997, Lensing et al.36 assessed 204 patients who were submitted to total knee and hip arthroplasty with the real-time B-mode US with compression of the venous segments, color-flow DS and phlebography. They obtained sensitivity of 60%, specificity of 96% and positive predictive value of 71% for proximal; 33.91% and 58%, respectively, for distal. They concluded that the color-flow DS does not increase the detection of asymptomatic DVT, when compared with the compression US, and thus should not be recommended for screening.

Nevertheless, Kalodiki et al.,37 in 1997, assessed 44 limbs of 23 asymptomatic patients using the US, focusing on the proximal segment without color. They obtained sensitivity of 56% and specificity of 94%. In 107 limbs of 55 patients, using the color, there was sensitivity of 93% and specificity of 99% for proximal; and 79% and 97%, respectively, for distal. They verified an improvement in the sensitivity for diagnosing the proximal segment, but believed that other studies would be necessary to corroborate these data.

Still in 1997, Mantoni et al.38 assessed 133 asymptomatic patients submitted to the surgery of hip fracture. By comparing the US with triplex (real time color-flow DS) with the phlebography, they obtained sensitivity of 74%, specificity of 99% and accuracy of 97% when assessing the lower limb. They reported that, when the thrombus is recent, it may result in false negative in the compression, but the color shows the partial thrombus. In the assessment, 29% of the segments were thought to be non-interpretable using the phlebography, and only 2% using the triplex. They believed that the power Doppler might increase the diagnostic accuracy in these cases.

In 1998, Davidson,39 in a literature review, reported that the DS in asymptomatic patients has low accuracy. High-quality studies, using the US with compression, color-flow duplex scanning and Doppler, showed sensitivity of 42-70% and positive predictive value of 35-83% for proximal DVT; for distal DVT, the accuracy proved to be low. They suggested that researches using improvements in the devices or contrast could increase the accuracy.

In 1998, Kearon et al.,40 in a review article, recommended phlebography as the only test for diagnosing asymptomatic patients. They believe that the abnormal US must be confirmed by phlebography. They reported sensitivity of 24-71% for B-mode, 23-57% for duplex, and 47-86% for color-flow.

However, in the reviews mentioned above, the articles by Kalodiki et al.37 and Mantoni et al.,38 published in 1997, were not evaluated.

In 2001, Bressollette et al.41 assessed 122 patients hospitalized at a medical clinic and performed the color-flow DS 48 hours after hospitalization, which was repeated at the fifth, eighth or 10th day and then every 5 days, during hospitalization, and after 3 months. The patients were assessed by the compression test of the venous segment and by the color-flow Doppler in all veins of lower limbs. They did not perform a comparative study between the DS and the phlebography in all patients. It was only made when the DS was altered. In the DS after 48 hours, 17 examinations were altered. Of these, five patients quit and 12 were submitted to the phlebography. The results showed sensitivity and specificity of 1, but there was statistical unconformity of the Kappa between two DS examiners.

In 2004, Elias et al.42 assessed 70 asymptomatic patients eight days after total hip arthroplasty, using the color-flow DS compared with phlebography, in a prospective study. They found sensitivity of 94% and specificity of 89% for all lower limb segments; for distal DVT, they only assessed sensitivity, which was 92%. They believe that the US could replace the phlebography for screening studies of new drugs. They noted that, in a few cases, the DS identified a thrombus that was not shown by the phlebography and that the DS might be better than the phlebography. By comparing with other studies, these authors used a more modern US device, with better image quality, and assessed all the venous segments of the limb. Despite having an increase in sensitivity, there was a decrease in specificity.

In Tables 1 and 2, we present a summary of the sensitivity and specificity results divided into proximal, distal and whole limb DVT, obtained by the authors mentioned in this article. In Table 1, we present the articles that used the B-mode US with compression test of venous segments. In Table 2, we present the articles that used the B-mode US and color-flow.

click hereTable 1 - Articles that used the B-mode ultrasound with compression test of venous segments

Author Whole limb Proximal Distal
SE SP SE SP SE SP
Borris et al.25 71% 94% 73% 96%
Agnelli et al.26 25% 99% 57% 99%
Koopman et al.29* 54% 98%
Agnelli et al.32 50%
Crippa et al.33 63% 98%
Kalodiki et al.37 56% 94%
Kearon et al.19* 24% 71%
* Literature review.
SE = sensitivity; SP = specificity.

click hereTable 2 - Articles that used the B-mode ultrasound with compression test of venous segments and color-flow

Author Whole limb Proximal Distal
SE SP SE SP SE SP
Davidson et al.27 38% 92%
Mattos et al.18 55% 98% 67% 100% 56% 98%
Wells et al.31* 62% 97% 48%
Magnusson34 58% 98% 62,5% 99,6% 53,6% 58%
Kalodiki et al.37 93% 99% 79% 97%
Lensing et al.36 60% 96% 33% 91%
Mantoni et al.38 74% 97%
Davidson39* 42-70%
Kearon et al.40* 47% 86%
Bressollette et al.41 100% 100%
Elias et al.42 95% 89% 92%
* Literature review.
SE = sensitivity; SP = specificity.

Based on these articles, which assessed the diagnosis for asymptomatic DVT by using the B-mode US, DS and color-flow DS, we noticed that, for the lower limb proximal segment, the sensitivity ranged from 38 to 67%. In only one study, the percentage was 93%,37 and the specificity ranged from 92 to 100%. Concerning the distal DVT, few studies assessed this segment, showing a significant decrease in sensitivity and specificity. When they assessed the lower limb, the sensitivity was around 55% and specificity was 98%. Only Elias et al.42 reported 95% of sensitivity and 89% of specificity, which can be considered an isolated article. The article by Bressollette et al.41 reports specificity and sensitivity of 1, but the DS was repeated at the fifth, eighth or 10th day, and then every 5 days during hospitalization, and after 3 months, which increases the chance of diagnosis, despite having performed the phlebography only when the DS was altered.

CONCLUSION

We can conclude that the DS, even using the color-flow, is not accurate yet to diagnosis the asymptomatic DVT, mainly when it affects the distal segment. The DS, for being specific, could be used to confirm, and not to exclude the DVT diagnosis. Thus, it is important to perform new studies using other techniques and/or equipment to assess the efficacy of the DS in the diagnosis of the asymptomatic DVT.

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