Isolated calf venous thrombosis: diagnosis with compression US

Asymptomatic Lower Extremity Deep Vein Thrombosis - Clinical Characteristics, Management Strategies, and Long-Term Outcomes

BACKGROUND

The prognosis of asymptomatic deep vein thrombosis (DVT) is uncertain and there is no consensus on the necessity of detection and treatment.Methods and Results:We retrospectively evaluated 300 patients with asymptomatic lower extremity DVT screened from 4,514 consecutive patients on ultrasound at Kyoto University Hospital between January 2010 and September 2015. The subjects had concomitant active cancer in 40%, unprovoked DVT in 59%, and distal DVT in 70%. The cumulative 5-year incidences of symptomatic recurrent venous thromboembolism (VTE); major bleeding; and all-cause death were 14.5%, 16.6%, and 34.1%, respectively. Among 232 patients (77%) with prolonged anticoagulant therapy, anticoagulants were discontinued in 48.4% at 1 year. Anticoagulant therapy was associated with a significantly higher incidence of major bleeding compared with the non-anticoagulant group (20.5% vs. 1.5%, P=0.01) with no significant effect on the incidence of VTE. In patients with active cancer, the favorable effect of anticoagulants relative to no anticoagulants for VTE was significant (HR, 0.22; 95% CI: 0.05-0.95).

CONCLUSIONS

Prolonged anticoagulants therapy was implemented in the majority of patients with asymptomatic DVT, but was associated with a significantly higher risk for major bleeding. On subgroup analysis in patients with active cancer, however, there appeared to be a benefit of prolonged anticoagulant therapy in decreasing the rate of symptomatic recurrent VTE.

Deep venous thrombosis following different isolated lower extremity fractures: what is known about prevalences, locations, risk factors and prophylaxis?

INTRODUCTION

Deep venous thrombosis (DVT) offers a high risk of morbidity and mortality, especially in case of pulmonary embolism. Precise data as to DVT after isolated lower extremity fractures (ILEFs) are rare. Even organizations like the American Academy of Orthopaedic Surgeons or the American College of Chest Physicians do not state exact recommendations as to optimal DVT prophylaxis (ppx) after ILEFs.

PREVALENCE

The incidence of DVT ranges from 5 to 86 % depending on the fracture whereas femur fractures offer the highest risk for clotting. The incidence seems to decrease in more distal fractures.

LOCATION

The risk to develop proximal clots is likely low, however, especially these are feared by surgeons. DVT can occur in both the injured and uninjured leg with a trend for higher incidences in the injured leg.

RISK FACTORS

Risk factors for DVT after ILEF seem to be similar to risk factors for DVT development after orthopaedic surgery and in general. Risk factors caused by surgeons are the use of a tourniquet, prolonged operative time and a delay from injury to surgery.

PROPHYLAXIS

Low molecular weight heparin is favoured by many authors, however, warfarin and acetylsalicylic acid are also used. Clear recommendations are still missing.

CONCLUSION

The rate of morbidity caused by DVT after ILEF is poorly understood so far. Exact data on prevalences are missing and optimal DVT prophylaxis still has to be defined.

Diagnosis of DVT: Antithrombotic Therapy and Prevention of Thrombosis, 9th ed: American College of Chest Physicians Evidence-Based Clinical Practice Guidelines

BACKGROUND

Objective testing for DVT is crucial because clinical assessment alone is unreliable and the consequences of misdiagnosis are serious. This guideline focuses on the identification of optimal strategies for the diagnosis of DVT in ambulatory adults.

METHODS

The methods of this guideline follow those described in Methodology for the Development of Antithrombotic Therapy and Prevention of Thrombosis Guidelines: Antithrombotic Therapy and Prevention of Thrombosis, 9th ed: American College of Chest Physicians Evidence-Based Clinical Practice Guidelines.

RESULTS

We suggest that clinical assessment of pretest probability of DVT, rather than performing the same tests in all patients, should guide the diagnostic process for a first lower extremity DVT (Grade 2B). In patients with a low pretest probability of first lower extremity DVT, we recommend initial testing with D-dimer or ultrasound (US) of the proximal veins over no diagnostic testing (Grade 1B), venography (Grade 1B), or whole-leg US (Grade 2B). In patients with moderate pretest probability, we recommend initial testing with a highly sensitive D-dimer, proximal compression US, or whole-leg US rather than no testing (Grade 1B) or venography (Grade 1B). In patients with a high pretest probability, we recommend proximal compression or whole-leg US over no testing (Grade 1B) or venography (Grade 1B).

CONCLUSIONS

Favored strategies for diagnosis of first DVT combine use of pretest probability assessment, D-dimer, and US. There is lower-quality evidence available to guide diagnosis of recurrent DVT, upper extremity DVT, and DVT during pregnancy.

Clinical relevance of distal deep vein thrombosis

PURPOSE OF REVIEW

To discuss pros and cons of anticoagulant treatment in the presence of symptomatic distal deep vein thrombosis.

RECENT FINDINGS

Available data are responsible for a lack of consensus regarding treatment of distal deep vein thrombosis.

SUMMARY

One standard diagnostic approach of suspected deep vein thrombosis consists of serial lower limb compression ultrasound of proximal veins. Studies evaluating compression ultrasound limited to the proximal veins performed on two occasions separated by 1 week showed good safety with a pooled estimate of the 3-month thromboembolic events rate of 0.6% (95% confidence interval: 0.4-0.9%) in untreated patients. However, performing two lower limbs compression ultrasound is cumbersome and expensive. Recently, studies using a single complete (proximal and distal) compression ultrasound showed a similar pooled estimate of the 3-month thromboembolic risk (0.3%, 95% confidence interval: 0.1-0.6%) but distal deep vein thrombosis accounted for as many as 50% of all diagnosed deep vein thrombosis in those series. Comparing these studies may suggest that systematically searching for calf deep vein thrombosis potentially doubles the number of patients given anticoagulant treatment without reducing the 3-month thromboembolic risk. Despite these data, many physicians still search for and treat distal deep vein thrombosis in the fear of proximal extension and of pulmonary embolism. However, robust data in favour of anticoagulation for distal deep vein thrombosis are limited. Randomized trials assessing the usefulness of anticoagulation in distal deep vein thrombosis are therefore urgently needed.

Is it worth diagnosing and treating distal deep vein thrombosis? No

The standard diagnostic approach to suspected deep vein thrombosis (DVT) is serial lower limb compression ultrasound (CUS) of proximal veins. Although it only assesses the proximal veins, withholding anticoagulant treatment in patients with a negative CUS on day 1 and after 1 week has been proved safe. In particular, studies evaluating CUS limited to the proximal veins showed a good safety profile with a pooled estimate of the 3-month thromboembolic rate of 0.6% (95% CI, 0.4-0.9%) in non-anticoagulated patients. However, performing two lower limbs CUS is cumbersome and expensive. Recently, studies using a unique complete (proximal and distal) CUS showed a similar pooled estimate of the 3-month thromboembolic rate (0.3%; 95% CI, 0.1-0.6%) but distal DVTs accounted for as many as 50% of all diagnosed DVTs in those series. Comparing these studies may suggest that systematically searching for calf DVTs potentially doubles the number of patients given anticoagulant therapy and entails a risk of over-treatment. Admittedly, performing calf CUS is highly useful in diagnosing other conditions such as popliteal cyst, hematoma or muscle rupture. Performing a CUS limited to the popliteal site in the presence of calf pain may be not well accepted by the patient. However, the advantage of calf CUS in diagnosing venous thromboembolism appears to be at the least debatable. Data suggesting that anticoagulation is indicated for distal DVT are limited, and realizing systematic distal CUS entails a risk of over-treatment. There is an urgent need for randomized trials assessing the usefulness of anticoagulant treatment in distal DVT.

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.

Dynamic MR venography: An intrinsic benefit of time-resolved MR angiography

PURPOSE

To investigate the possibility of obtaining dynamic contrast-enhanced magnetic resonance venography (DCE-MRV) images of the lower extremities.

MATERIALS AND METHODS

Peripheral contrast-enhanced magnetic resonance angiography (CE-MRA) was performed on 20 patients using a time-resolved sequence that combined undersampled projection reconstruction (PR) in-plane and Cartesian slice encoding through-plane. The contrast dynamics of distal vessels were depicted. An automated segmentation algorithm based on a contrast arrival time (CAT) threshold was used to generate contrast dynamics in the venous system. The signal difference between the vein and artery was measured to evaluate the effectiveness of this technique in isolating the venous contrast dynamics.

RESULTS

The automatically generated image series depicted the contrast dynamics of both the arterial and venous systems, including asymmetric venous enhancement and background tissue enhancement. Quantitative measurement showed a mean venous/arterial signal ratio increase from 1.58 to 4.82 for the peak venous frame after arterial signal suppression.

CONCLUSION

DCE-MRV is a minimally invasive technique for evaluating the venous side of the systemic vascular anatomy. Time-resolved MRA has the potential clinical benefit of enabling both arterial and venous disease to be detected in patients undergoing CE-MRA.

Systematic review and meta-analysis of the diagnostic accuracy of ultrasonography for deep vein thrombosis

BACKGROUND

Ultrasound (US) has largely replaced contrast venography as the definitive diagnostic test for deep vein thrombosis (DVT). We aimed to derive a definitive estimate of the diagnostic accuracy of US for clinically suspected DVT and identify study-level factors that might predict accuracy.

METHODS

We undertook a systematic review, meta-analysis and meta-regression of diagnostic cohort studies that compared US to contrast venography in patients with suspected DVT. We searched Medline, EMBASE, CINAHL, Web of Science, Cochrane Database of Systematic Reviews, Cochrane Controlled Trials Register, Database of Reviews of Effectiveness, the ACP Journal Club, and citation lists (1966 to April 2004). Random effects meta-analysis was used to derive pooled estimates of sensitivity and specificity. Random effects meta-regression was used to identify study-level covariates that predicted diagnostic performance.

RESULTS

We identified 100 cohorts comparing US to venography in patients with suspected DVT. Overall sensitivity for proximal DVT (95% confidence interval) was 94.2% (93.2 to 95.0), for distal DVT was 63.5% (59.8 to 67.0), and specificity was 93.8% (93.1 to 94.4). Duplex US had pooled sensitivity of 96.5% (95.1 to 97.6) for proximal DVT, 71.2% (64.6 to 77.2) for distal DVT and specificity of 94.0% (92.8 to 95.1). Triplex US had pooled sensitivity of 96.4% (94.4 to 97.1%) for proximal DVT, 75.2% (67.7 to 81.6) for distal DVT and specificity of 94.3% (92.5 to 95.8). Compression US alone had pooled sensitivity of 93.8 % (92.0 to 95.3%) for proximal DVT, 56.8% (49.0 to 66.4) for distal DVT and specificity of 97.8% (97.0 to 98.4). Sensitivity was higher in more recently published studies and in cohorts with higher prevalence of DVT and more proximal DVT, and was lower in cohorts that reported interpretation by a radiologist. Specificity was higher in cohorts that excluded patients with previous DVT. No studies were identified that compared repeat US to venography in all patients. Repeat US appears to have a positive yield of 1.3%, with 89% of these being confirmed by venography.

CONCLUSION

Combined colour-doppler US techniques have optimal sensitivity, while compression US has optimal specificity for DVT. However, all estimates are subject to substantial unexplained heterogeneity. The role of repeat scanning is very uncertain and based upon limited data.

Deep venous thrombosis: withholding anticoagulation therapy after negative complete lower limb US findings

PURPOSE

To establish the safety of withholding anticoagulation therapy after negative findings at a complete lower limb ultrasonographic (US) examination of the symptomatic leg for suspected deep venous thrombosis (DVT).

MATERIALS AND METHODS

Regional ethics committee approval and patient consent were obtained. A total of 542 consecutive ambulatory patients presented to the emergency department and were prospectively recruited from April 2001 to May 2003. Of these patients, 16 were excluded, and radiology residents and sonographers performed a complete lower limb US examination by means of compression and Doppler US in 526 patients. Patients with negative US findings received no anticoagulation therapy, and they were observed for occurrence of any thromboembolic event for 3 months. Patients with progressive or new symptoms that were indicative of thromboembolism within the follow-up period underwent objective testing with US, computed tomographic (CT) pulmonary angiography, or both.

RESULTS

There were 413 patients (78.5%) with US findings that were negative for DVT and 113 patients (21.5%) with findings that were positive. There were 64 patients (56.6%) with DVT isolated to the calf and 49 (43.4%) with proximal DVT. Of the 413 patients with negative initial US findings, 16 (3.9%) underwent a second US examination for new or progressive symptoms of DVT, one patient (0.25%) underwent CT pulmonary angiography for suspected pulmonary embolism, and one patient (0.25%) underwent both US and CT pulmonary angiography during the 3-month follow-up period. One of these patients (0.24%; 95% confidence interval: 0.01%, 1.3%) developed pulmonary embolism, which was diagnosed with CT pulmonary angiography. DVT was not diagnosed in any patient, and no patient died during follow-up. The negative predictive value of a complete single lower limb US examination to exclude clinically important DVT is 99.6% (95% confidence interval: 98.4%, 99.9%).

CONCLUSION

A single negative complete lower limb US examination is sufficient to exclude clinically important DVT, and it is safe to withhold anticoagulation therapy after negative complete lower limb US findings were obtained in patients suspected of having symptomatic lower limb DVT. New or progressive symptoms require further objective imaging.

Extended versus rapid analysis of the leg vein system: a multicenter ultrasound study (the ERASMUS study)--an interim analysis

The reliability of diagnostic strategies based on compression ultrasonography (CUS) for the diagnosis of proximal deep venous thrombosis (DVT) in symptomatic (out)patients is well documented; however these approaches never gained widespread application.Echo-color-Doppler (ECD), is regularly adopted by vascular laboratories as first line test in case of clinically suspected DVT, although the specificity of calf veins imaging is uncertain, as is the negative predictive value of a normal ECD workup. To date, no direct comparison of these strategies is available in the literature. We designed a randomised prospective study to compare the safety and feasibility of two diagnostic approaches: a "rapid" (CUS + D-dimer), and an "extended" strategy (ECD of the whole-leg). All consecutive patients with suspected symptomatic DVT of the legs, if at their first episode, and if not meeting exclusion criteria, will be enrolled in the study. The primary outcome of the study will be the rate of symptomatic VTE during a 3-month follow-up, after a normal diagnostic workup with either of the two proposed strategies. All events will be adjudicated by a blind and independent committee, based on the results of objective testing. An interim data analysis will be presented during the congress session.

Sonography and venography of the lower extremities for diagnosing deep vein thrombosis in symptomatic patients

The purpose of this study was to investigate the efficacy of sonography and the frequency of indeterminate sonographic examinations in the evaluation of patients with suspected lower extremity deep vein thrombosis (DVT). We prospectively evaluated 136 symptomatic patients (157 extremities) with suspected DVT using sonography and contrast-enhanced venography (n=106 patients, 115 extremities). Using venography as the reference standard for diagnosing DVT, the sensitivity and specificity of sonography was 92.8% and 98%, respectively, yielding an accuracy of 96.8%. The frequency of indeterminate examinations for calf DVT was 32.4%. One (0.7%) fatal pulmonary embolus occurred in our patients. The pulmonary embolism (PE) rate was 1.6% after lower extremity sonography with negative results. Sonography is highly accurate in detecting lower extremity DVT in symptomatic patients. Because of the high frequency of indeterminate studies in the calf and the associated possible risk of pulmonary emboli, we urge radiologists exercise additional caution when evaluating symptomatic patients with clinically suspected lower extremity DVT.

Flow-independent magnetic resonance venography of the calf

PURPOSE

To show that flow-independent venography that exploit the intrinsic MR properties of blood to isolate vessels from surrounding structures can be used for depiction of peripheral veins and for detection of deep venous thrombosis (DVT).

MATERIALS AND METHODS

Sequence and parameters were first determined on a theoretical basis. The sequence was then optimized in volunteers (N = 4) for the depiction of the peripheral venous vessels. Qualitative evaluation of the normal venous anatomy was performed in five volunteers. The feasibility of diagnosing DVT of the calf with this method was evaluated with preliminary clinical studies.

RESULTS

Excellent depiction of the venous anatomy was achieved in all volunteers with the optimized technique. Very small venous structures, such as superficial, muscular, and perforator veins, were clearly depicted because of the high spatial and contrast resolution capacities of the sequences. In all six patients, DVT findings diagnosed by duplex sonography were also seen on MR venography.

CONCLUSION

Venous anatomy mapping and detection of lower-limb DVT appear feasible using flow-independent MR venograms.

Proximal extent of pelvic vein thrombosis and its association with pulmonary embolism

OBJECTIVE

Conventional methods such as duplex ultrasound scanning do not provide accurate information about proximal extension of pelvic vein thrombosis. We evaluated proximal extent of thrombus toward pelvic veins with magnetic resonance imaging in patients with suspected deep vein thrombosis (DVT) proximal to the inguinal ligament on the basis of duplex ultrasound scans. In addition, frequency of pulmonary embolism (PE) and early (4 weeks) clinical outcome were evaluated.

METHODS

Two hundred twelve patients with acute symptomatic DVT proximal to the inguinal ligament, diagnosed at duplex ultrasound scanning, were enrolled in this prospective study. All patients underwent magnetic resonance imaging of the abdominal and pelvic veins, as well as lung scintigraphy to detect the presence of pulmonary embolism.

RESULTS

In 24 of 212 patients (11%), thrombus was restricted to the femoral vein. The thrombus extended into iliac veins in 142 patients (67%) and into the inferior vena cava in 46 patients (22%). The frequency of PE was not associated with the most proximal extension of thrombus (P =.61). No patients died as a consequence of thromboembolic events.

CONCLUSIONS

Extension of DVT into the inferior vena cava occurs relatively frequently. In our patients this finding was not associated with higher risk for PE compared with DVT of the femoral or iliac veins.

[Diagnosis of deep venous thrombosis of the lower limbs: performance of diagnostic tests]

Deep-vein thrombosis is a frequent affection that needs precise diagnosis. Indeed, the clinical complications (from post-thrombotic syndrome to fatal pulmonary embolism) as well the risk of anticoagulant treatment require a precise diagnosis. Since clinical evaluation cannot assure reliably diagnosis by lack of sensitivity and specificity, complementary exams are needed. However, clinical assessment is an important part to decide further examinations. D-dimers assessment allows to role out the diagnosis of deep-vein thrombosis in a number of cases. Plethysmography and continuous Doppler are progressively given up. Compressive venous ultrasonography is now the exam of first choice. Scintigraphy, scanner and RMI must still be validated. Phlebography remains the gold standard in case of negative compressive venous ultrasonography and a high clinical probability.

Algorithms for the diagnosis of deep-vein thrombosis in patients with low clinical pretest probability

The objective of this current trial was to evaluate the rate of deep-vein thrombosis (DVT) in patients after low clinical risk stratification and to evaluate the value of D-dimer and different imaging techniques in the diagnostic algorithm. A total of 99 consecutive patients were included in this prospective trial. After clinical risk assessment, D-dimer was determined. Final diagnosis was based on the results of duplex sonography, in cases of indeterminate scans on those of ascending venography. Three months after admission, follow-up investigations were performed by a telephone interview to evaluate possible further venous thromboembolism. Final diagnosis was based on the results of colour Doppler ultrasound in 92.9% and on those of venography in 7.1%. DVT was diagnosed in 2%, D-dimer was positive in 48.4%, giving a sensitivity of 100%, a specificity of 52.7% and a negative predictive value of 100%. Follow-up was possible in 89.9%--no further thromboembolic event occurred. In this specific patient group, a negative D-dimer excludes DVT and can therefore reduce the number of imaging procedures by one-half, which, on the contrary, is necessary in patients with positive D-dimer.

Isolated calf vein thrombosis: comparison of MR venography and conventional venography after initial sonography in symptomatic patients

RATIONALE AND OBJECTIVES

The authors performed this study to compare magnetic resonance (MR) venography and conventional venography in the diagnosis of deep venous thrombosis (DVT) in the calf after sonography.

MATERIALS AND METHODS

Sonography was performed in 595 patients who were suspected of having lower-extremity DVT. Patients with positive above-knee duplex sonograms, allergy to iodinated contrast material, renal insufficiency, or cardiac pacemakers and patients who were obese were excluded. The remaining 73 patients were asked to undergo MR venography and conventional venography. All studies were to be performed within 48 hours of the clinical diagnosis and according to standard clinical practice. Images were interpreted by radiologists who were blinded to the results of other modalities. Two separate analyses were performed: one in which conventional venography was used as the standard of reference, and one in which the presence of at least two positive studies for thrombus was considered diagnostic.

RESULTS

Although 36 patients agreed to participate in the study, only 14 underwent MR venography and conventional venography within 48 hours of the clinical diagnosis. With use of any two positive studies for confirmation, acute DVT was diagnosed in three patients. Conventional venography depicted two of the three cases, whereas sonography and MR venography each depicted all three. The findings were concordant in only five of the 14 patients.

CONCLUSION

Moderate discrepancy among modalities was demonstrated. This suggests radiologists should undertake comparisons among these three modalities for the detection of calf DVT. In patients with a high clinical suspicion, a second modality may be useful if the initial study is negative.

Ultrasound with Levovist in the diagnosis of suspected calf vein thrombosis

Diagnosing calf vein thrombosis (CVT) by color Doppler ultrasound (US) is often a difficult task because of swelling or obesity. The purpose of this study was to assess if IV infusion of Levovist can improve the accuracy and reduce the rate of indeterminate examinations. A total of 20 patients with suspected CVT underwent color Doppler US without and with Levovist followed by ascending venography as the "gold standard," which detected calf clots in 7 patients (35%). Compared to routine noncontrast sonography, Levovist examination reduced the rate of indeterminate scans from 55% to 20% and improved the specificity for the detection of CVT from 25% to 67% without compromising sensitivity (100% to 86%) notably. Image quality was improved in 13 (65%) of 20 scans. In conclusion, we can say that Levovist improves the quality of duplex examination of the calf veins, especially in cases with difficult conditions due to obesity or swelling.

Optimal management strategy for use of compression US for deep venous thrombosis in symptomatic patients: a cost-effectiveness analysis

RATIONALE AND OBJECTIVES

The authors' purpose was to identify the optimal strategy for using compression ultrasonography (US) in patients suspected of having deep venous thrombosis (DVT).

MATERIALS AND METHODS

The authors developed a decision-analytic model representing the natural history of DVT and the benefits and risks of anticoagulation therapy. They evaluated six initial imaging strategies: (a) unilateral examination of the common femoral and popliteal veins; (b) unilateral examination of the common femoral, popliteal, and femoral veins; (c) bilateral examination of the common femoral and popliteal veins; (d) bilateral examination of the common femoral, popliteal, and femoral veins; (e) complete unilateral examination of the symptomatic leg (including calf veins); and (f) complete bilateral examination of both legs.

RESULTS

For 65-year-old men with unilateral symptoms of DVT, the most effective strategy was bilateral examination of the common femoral and popliteal veins with anticoagulation therapy in patients with proximal DVT and follow-up bilateral examination of the common femoral and popliteal veins in patients without an initial diagnosis of DVT with an incremental cost-effectiveness ratio of $39,000 per quality-adjusted life year gained.

CONCLUSION

These results suggest that bilateral examination limited to the common femoral and popliteal veins, with follow-up bilateral examination limited to the common femoral and popliteal veins, was as cost-effective as other well-accepted medical interventions. The results were sensitive to the distribution of clot, diagnostic accuracy of compression US, and probability of bleeding with long-term morbidity.

Acute Calf Vein Thrombosis: Outcomes and Implications

The purpose of this study was to define the incidence of and outcomes associated with isolated acute calf vein thrombosis (CVT). From 11/95 through 6/97, 3096 patients underwent lower extremity venous duplex testing in a hospital-based vascular laboratory in which bilateral tibial and peroneal vein imaging were standard components of the venous duplex examination. CVT was present in 118 patients (3.8%), and 339 patients (10.9%) had acute proximal deep venous thrombosis (PDVT). Patients with CVT were 56.4 ± 17.2 years of age (range, 18–92). Approximately 25 per cent with CVT had cancer (n = 30). Of the 18 patients with CVT who underwent ventilation-perfusion (V/Q) lung scanning, 56 per cent (n = 10) had high-probability scans. Venous duplex reports for those with CVT recommended follow-up venous duplex examination, which was done in 60 per cent (n = 71) of patients. Of the 71 patients with CVT who underwent follow-up testing, 15.5 per cent (n = 11) progressed to PDVT. The incidence of progression to deep venous thrombosis was 25 per cent (9 of 36) in those receiving anticoagulants at the time of initial venous duplex examination versus 5.7 per cent (2 of 35) in those not receiving anticoagulants (P = 0.046). With progression to PDVT, patients were more likely to have cancer (35% versus 7.8%; P = 0.009), more likely to have high-probability V/Q scans (36% versus 6.7%; P = 0.017), and more likely to die (27% versus 1.7%; P = 0.011) during follow-up. CVT was less common than proximal deep vein thrombosis and was also associated with pulmonary embolism. Progression of CVT was an adverse clinical event associated with greater chance of pulmonary embolism and death.

Calf sonography for detecting deep venous thrombosis in symptomatic patients: experience and review of the literature

PURPOSE

We determined the accuracy of sonography in the detection of isolated calf deep venous thrombosis (DVT) and the rate of indeterminate ultrasound examinations in patients with physical signs or symptoms suggestive of DVT.

METHODS

We reviewed the medical literature (MEDLINE) to determine the accuracy of sonography and the frequency of indeterminate studies in detecting isolated calf DVT in patients with physical signs or symptoms suggestive of DVT. A meta-analysis was used to derive summary measures of sensitivity, specificity, and accuracy from studies in which 5 or more isolated calf DVT were identified. Frequencies of indeterminate examinations were recorded for studies in which these data were provided, and we pooled these results with our own data for 196 patients.

RESULTS

The meta-analysis revealed that sonography correctly identified isolated calf DVT in 49 of 53 extremities (sensitivity, 92.5%; 95% confidence interval, 81.8-97.9%) and correctly identified the absence of calf DVT in 157 of 159 extremities (specificity, 98.7%; 95% confidence interval, 95.5-99. 9%), yielding an accuracy of 97.2% (95% confidence interval, 93.9-99. 0%) for ultrasound examinations considered diagnostic. However, when evaluating our patient population and the literature, we found a substantial number of indeterminate studies (overall rate of 54.6% in 463 extremities), with a wide variation in the reported frequency of indeterminate studies (9.3-82.7%).

CONCLUSIONS

Sonography is highly accurate in detecting isolated calf DVT in symptomatic patients, but indeterminate studies occur frequently, with a wide range of reported rates. Each ultrasound laboratory should evaluate its own rate of indeterminate studies.

Imaging evaluation of suspected pulmonary embolism

Venous thromboembolism (VTE) is a common disorder that is difficult to diagnose clinically but carries significant morbidity and mortality if untreated. Additionally, although demonstrated to be of benefit in cases of proven deep vein thrombosis (DVT) and pulmonary embolism (PE), anticoagulation therapy is not without risk. Because the clinical exam is known to be unreliable for the detection of both DVT and PE, many imaging modalities have been used in the diagnostic imaging algorithm for the detection of VTE, including chest radiography, ventilation/perfusion (V/Q) scintigraphy, pulmonary angiography, and recently, spiral computed tomography (CT) and magnetic resonance imaging (MRI). Chest radiographic findings in acute PE include focal oligemia, vascular enlargement, atelectasis, pleural effusions, and air space opacities representing pulmonary hemorrhage or infarction. The chest radiograph can occasionally be suggestive of PE but is more often nonspecifically abnormal. The main use of the chest radiograph in the evaluation of suspected PE is to exclude entities that may simulate PE and to assist in the interpretation of V/Q scintigraphy. Lower extremity venous compression ultrasonography (CU) is both sensitive and specific for the diagnosis of femoropopliteal DVT, and the value of negative CU results has been established in outcomes studies. However, the reliability of CU for the detection of isolated calf vein thrombosis is not well established, and the clinical significance of such thrombi is debatable. Additional methods such as color and spectral Doppler analysis are also useful in the diagnostic evaluation of DVT but are best considered as adjuncts to the conventional CU examination rather than as primary diagnostic modalities themselves. Compression ultrasonography and Doppler techniques are useful in the evaluation of suspected upper extremity DVT; spectral Doppler waveform analysis is particularly useful to assess for the patency of veins that cannot be directly visualized and compressed with conventional gray-scale sonography. V/Q scintigraphy has been the initial modality obtained in patients suspected of PE for a number of years. Although many studies have investigated the role of V/Q scintigraphy in the evaluation of VTE, the Prospective Investigation of Pulmonary Embolism Diagnosis (PIOPED) study has provided the most useful information regarding the utility of V/Q scintigraphy in this setting. A high probability scan interpretation is sufficient justification to institute anticoagulation, and a normal perfusion scan effectively excludes the diagnosis of PE. A normal/near normal scan interpretation also carries a sufficiently low prevalence of angiographically proven PE to withhold anticoagulation. Although the prevalence of PE in the setting of low probability scan interpretations is low and several outcomes studies have demonstrated a benign course in untreated patients with low probability scan results, patients with inadequate cardiopulmonary reserve do not necessarily have good outcomes. Such patients deserve more aggressive evaluation. Patients with intermediate probability scan results have a 20% to 40% prevalence of angiographically proven PE and thus require further investigation. The radionuclide investigation of DVT includes such techniques as radionuclide venography and thrombus-avid scintigraphy. Although these methods have not been as thoroughly evaluated as CU, studies thus far have indicated encouraging results, and further investigations are warranted. Pulmonary angiography has been the gold standard for the diagnosis of PE for decades. Studies have indicated that angiography has probably been underutilized by referring physicians for the evaluation of suspected PE, likely because of the perception of significant morbidity and mortality associated with the procedure. (ABSTRACT TRUNCATED)

Deep venous thrombosis: complete lower extremity venous US evaluation in patients without known risk factors--outcome study

PURPOSE

To determine the diagnostic value of venous ultrasonography (US) that includes examination of calf veins in symptomatic patients suspected of having deep venous thrombosis (DVT) of the lower extremities.

MATERIALS AND METHODS

A retrospective cohort study of the prevalence of DVT included 977 consecutive patients with possible DVT but without known risk factors for DVT. Color flow and compression US were performed. The outcome was the frequency of overlooked, clinically important DVT after negative initial results from bilateral venous US of above- and below-the-knee veins. Patient records (904 patients), mailed questionnaires (61 patients), and telephone contacts (12 patients) were used to establish a diagnosis of clinically relevant DVT.

RESULTS

The prevalence of DVT was 15% (142 of 977), with DVT in 15% (21 of 142) restricted to the below-the-knee veins. Follow-up (median, 34 months) in 835 patients with negative US findings showed one occurrence of venous thrombosis (superficial thrombophlebitis) during the first 3 months of follow-up. Three other cases of venous thrombosis occurred at 17, 18, and 48 months of follow-up but were believed not to be linked to the initial complaint. The incidence of overlooked DVT was 0% (95% CI, 0.0%, 0.4%).

CONCLUSION

In patients without risk factors for DVT, a negative venous US study can help exclude the presence of clinically important DVT if the examination includes careful evaluation of the calf veins.

The use of power Doppler ultrasound in the diagnosis of isolated deep venous thrombosis of the calf

While ultrasound has been well accepted as an accurate test for the diagnosis of both femoral and popliteal deep venous thrombosis (DVT), its role in the detection of calf DVT has been less clear. There have been variable results between studies in the accuracy of colour Doppler or compression sonographic techniques in demonstrating calf DVT. Many of these studies have suffered from high rates of technically inadequate examinations. Power Doppler (colour Doppler energy) has a higher sensitivity than conventional colour Doppler. It should therefore allow the detection of slow venous flow in patent vessels, that may not be demonstrated by conventional colour Doppler. This should decrease the number of technically inadequate examinations as well as decreasing the false-positive rate of the test. A prospective blinded reader study was undertaken comparing power Doppler to the gold standard venography, in the diagnosis of isolated calf deep venous thrombosis (DVT). Both examinations were successfully performed in 50 patients, in whom proximal DVT had been excluded by compression ultrasonography. Fifteen patients had positive evidence of an isolated calf DVT on the gold standard technique, venography. Power Doppler demonstrated a sensitivity of 100%, a specificity of 79%, a positive predictive value of 71% and a negative predictive value of 100%, in detecting an isolated calf DVT. There were no technically inadequate ultrasound examinations. Where venous flow is demonstrated, power Doppler is a highly accurate test in excluding a calf DVT. The specificity of the test, however, is limited, as the absence of flow does not always signify a DVT.

Diagnostic management of venous thromboembolism

The accuracy of diagnostic methods for the diagnosis of deep vein thrombosis and pulmonary embolism in symptomatic patients is critically reviewed. In addition, the safety of withholding anticoagulant therapy from patients with suspected deep vein thrombosis or pulmonary embolism in whom the qualified diagnostic strategy was normal is evaluated by determining the frequency of venous thromboembolic complications during 3 months of follow-up. It is shown that the currently used available diagnostic techniques for deep vein thrombosis are all able to identify the majority of patients who indeed have venous thrombosis. However, as result of its accuracy and practical advantages, compression ultrasound is the test of choice in the evaluation of symptomatic patients. Patients with a normal test outcome should be re-tested to detect the small proportion of patients with proximally extending calf vein thrombosis. In the strategy of repeated diagnostic testing, impedance plethysmography could be used as an alternative to ultrasonography. To obtain a reduction in repeat tests various diagnostic strategies have been evaluated and it was shown that these strategies, using non-invasive tests, can be as accurate and safe as the invasive reference strategy. The safeties of the various strategies were very similar; however, important differences were observed with respect to the practical implementation of the various diagnostic strategies. Simplification of the repeated testing strategy by using a D-dimer assay and/or a clinical decision rule seems to be promising. The reference standard for the diagnosis of pulmonary embolism remains pulmonary angiography. Several strategies based on non-invasive diagnostic methods have been evaluated for their safety and complexability. Perfusion-ventilation lung scanning is the most thoroughly evaluated non-invasive technique so far. It seems safe to withhold anticoagulant therapy in patients suspected of pulmonary embolism with a normal perfusion lung scan result; however, further testing is needed in the case of a non-diagnostic perfusion-ventilation lung scan result. At this moment angiography is the method of choice in this category of patients. D-dimer assays, clinical decision rules and ultrasound examinations of the legs seem to have a high potential to limit the need for angiography. Also, spiral computerized tomography and magnetic resonance imaging are promising techniques, but their role in the diagnostic management of pulmonary embolism is still uncertain.

Duplex ultrasound in the hemodynamic evaluation of the late sequelae of deep venous thrombosis

PURPOSE

The use of duplex ultrasound scanning to evaluate the hemodynamic outcome of deep venous thrombosis 7 to 13 years after the original diagnosis.

METHODS

Duplex ultrasound was used to re-examine 1212 segments of vein from 72 patients (49 men, 23 women) with deep venous thrombosis previously diagnosed by means of phlebography to detect reflux and obstruction and evaluate flow; 611 segments were initially thrombosed and 601 segments were open. To define reflux, reversed flow in 31 healthy persons was measured.

RESULTS

In a review of all veins of the 72 patients, 8 patients (11%) had completely normal duplex results in all veins, 33 (46%) had reflux, 6 (8%) had at least one noncompressible vein segment, and 25 (35%) had a combination of both. In the proximal vein segments without initial thrombosis a higher percentage was normal (73%) than in segments with initial thrombosis (46%). There was a significantly higher frequency of reflux (46%, p = 0.05) and noncompressibility (12%, p < 0.01) in initially thrombosed proximal vein segments than in vein segments without initial thrombosis (reflux 25%, noncompressibility 3%). Distal to the knee 125 (17%) of 720 vein segments were not traceable. Significantly more initially thrombosed vein segments were not traceable (p < 0.01). In distal vein segments there was no significant difference in reflux (7% versus 5%) and noncompressibility (10% versus 5%) between vein segments with and without initial thrombosis. Flow was present in 99% of the 611 previously thrombosed proximal and distal segments.

CONCLUSIONS

Most patients with deep venous thrombosis still had venous abnormalities 7 to 13 years after the initial diagnosis. The most common abnormality was reflux. Significantly more abnormalities were found in initially thrombosed segments. The abnormalities were found in the proximal vein segments and in the distal vein segments, although less frequently in the latter.

Diagnosis of acute lower limb deep venous thrombosis with ultrasound: trends and controversies

Acute deep venous thrombosis of the lower limb is a common and threatening condition whose clinical diagnosis is known to be unreliable. Sonography has gradually superseded venography as the primary diagnostic procedure. A review of the medical literature shows that sonography offers a high level of sensitivity and specificity in symptomatic patients but suffers from a lack of sensitivity at the calf level and in asymptomatic patients. Technologic progress, as well as increased operator experience, may improve sensitivity. Nevertheless, several critical issues remain unresolved, such as the significance of free-floating thrombi, the usefulness of calf and bilateral examination, the criteria that are essential to the diagnosis, the risk of compression sonography, and sonography's role in the direct detection of venous emboli.

Calf vein thrombosis in spinal cord injured patients: conservative management of two cases

Several studies have suggested that if a calf vein thrombosis does not propagate above the knee when followed up with serial diagnostic studies, full anticoagulation may not be necessary. These studies have not included spinal cord injured patients. Two patients with spinal cord injury were diagnosed with acute calf vein thrombosis after admission to a spinal cord injury rehabilitation unit. Both patients refused intravenous heparinization. Serial duplex Doppler studies were performed on both patients to evaluate for propagation of thrombus. Neither patient developed propagation of thrombus, pulmonary embolus, or persistent thrombophlebitis. Full anticoagulation including intravenous heparinization is costly, subject to complications, and interferes with intensive rehabilitation therapies. Observation of calf vein thrombosis with appropriate serial follow-up studies may be a viable alternative to anticoagulation in spinal cord injured patients. Further studies need to be done with this unique patient population.

Detection of deep venous thrombosis: prospective comparison of MR imaging and sonography

Seventy-five patients (41 women and 34 men, 20-85 years old) with clinically suspected deep venous thrombosis (DVT) were examined with MR imaging and sonography. In 26 patients, the final diagnosis was acute femoropopliteal DVT. The sensitivity of MR imaging for detecting this disease was 100% with a 95% confidence interval (CI) of 87-100%; the specificity was 100% with a CI of 92-100%; and the accuracy was 96% with a CI of 89-99%. The correspond-ing sensitivity of sonography was 77% with a CI of 53-92%; the specificity was 98% with a CI of 89-100%; and the accuracy was 83% with a CI of 72-90%. In four of the 75 patients, MR images revealed thrombus of the pelvis (n = 1) or calf (n = 3) without femoropopliteal involvement. The estimated prevalence of isolated calf and/or pelvic DVT was 5% with a CI of 1-13%. MR imaging is significantly more sensitive (P = .02) and accurate (P < .01) than sonography in the detection of lower extremity DVT, but there was no difference in the specificity of MR imaging and that of sonography (P = .31).

Incidence of deep vein thrombosis after arthroscopic knee surgery: a prospective study

Deep vein thrombosis (DVT) with subsequent pulmonary emboli (PE) is the most life-threatening complication of knee arthroscopy. Although the incidence of clinically diagnosed DVT after arthroscopy is low, clinical examination is less sensitive and specific than other diagnostic modalities for the detection of venous clot. This study used compression ultrasound to prospectively evaluate patients before and after arthroscopic surgery for the presence of DVT. Preoperatively, patients were screened for DVT risk factors. Eighty-five patients completed the study. Three asymptomatic "silent" DVTs were identified, for an incidence of 3.5%. There was no statistically significant difference between those with and without risk factors for the development of DVT.

Colour-assisted compression ultrasound in the diagnosis of calf deep venous thrombosis

OBJECTIVE

To determine sensitivity and specificity of colour-assisted compression ultrasound (CUS) in the diagnosis of deep venous thrombosis (DVT) isolated to the calf veins.

DESIGN

Prospective comparison of CUS with contrast venography in patients undergoing both procedures, with blinded evaluation of results.

SETTING

Alfred Hospital, Melbourne (an urban tertiary referral hospital), between November 1990 and May 1992.

SUBJECTS

Patients presenting for contrast venography with signs or symptoms of lower limb DVT.

OUTCOME MEASURES

Presence of DVT; technical adequacy of examination.

RESULTS

92 of 402 patients (104 limbs) were examined. DVT was detected by venography in 43 limbs and was isolated to the calf veins in 19. It was diagnosed by CUS for eight of these 19. Calf CUS was technically inadequate in 26 limbs. Sensitivity and specificity of CUS for isolated calf DVT were 67% (95% confidence interval [CI], 40%-94%) and 93% (95% CI, 83%-100%), respectively, when the CUS was adequate. The low sensitivity of CUS was related to small size of the thrombi, inadequate studies because of previous DVT or very swollen limbs and technical errors.

CONCLUSION

CUS is accurate for detecting larger isolated calf DVT when the calf study is adequate. Including the calf veins as well as the femoropopliteal veins in the initial CUS examination for symptomatic suspected lower limb DVT may reduce the need for follow-up CUS.

Utility of leg ultrasonography in suspected symptomatic isolated calf deep venous thrombosis

PURPOSE

To evaluate the utility of duplex ultrasonography in patients with suspected symptomatic, isolated calf deep venous thrombosis.

PATIENTS AND METHODS

Thirty patients with clinically suspected isolated calf deep venous thrombosis were examined with both duplex ultrasonography and contrast venography and the results were compared.

RESULTS

Venography detected 7 cases of isolated calf deep venous thrombosis, all of which were also detected by ultrasonography. Ultrasound identified an additional 3 cases of soleal vein thrombosis, but venography did not visualize these veins. Of the 20 negative ultrasound studies, 11 were technically inadequate; however, no false-negative ultrasound studies were noted.

CONCLUSIONS

Compression ultrasonography may be reliable for the evaluation of patients with suspected symptomatic infrapopliteal deep venous thrombosis. Its apparent superiority to contrast venography in visualizing muscular calf veins warrants further study; however, the high rate of technical inadequacy in ultrasound studies observed here, if confirmed in larger studies, may limit the usefulness of ultrasound in this setting.

[Color-coded duplex ultrasound as a screening method in trauma surgery]

Deep vein thrombosis with consecutive pulmonary embolism is one of the most important complications for trauma patients. At the University Hospital of Mainz, Department of Traumatology, colour duplex ultrasound is used as screening method in trauma patients. Fractures of thoracic and lumbal spinal bones, pelvis, hip and lower extremities, endoprosthesis of hip and knee joints and longer immobilisation are considered as special risk for the genesis of deep vein thrombosis. Out of 326 patients investigated with colour duplex ultrasound, 24 patients suffered from unknown deep vein thrombosis, 8 developing pulmonary embolism. We recommend colour duplex sonography on day 10, after the third week, and after longer immobilisation. Colour duplex sonography provides an easy performable and noninvasive method for screening evaluation of deep vein thrombosis in trauma patients.

Lower limb deep venous thrombosis: a critical view of ultrasound

The replacement of venography with ultrasound in investigation of lower limb deep venous thrombosis (DVT) is a trend that generally has been appropriate. However, there is substantial variation in reported accuracies related to different clinical contexts, operator experience and sophistication of equipment. The best and most consistent results are for suspected acute femoropopliteal thrombosis, while there is variation in accuracy and diagnostic approach for below knee thrombosis. Potential exists for substantial diagnostic inaccuracy for suspected recurrent DVT, in surveillance of high-risk patients and in patients with possible pulmonary embolism. The choice of ultrasound over contrast venography should take account of local expertise and accuracy, availability of resources, clinical indication for investigation and cost-effectiveness.

Diagnostic utility of color Doppler ultrasound in lower limb deep vein thrombosis in patients with clinical suspicion of pulmonary thromboembolism

The diagnosis of pulmonary thromboembolism is frequently based on ventilation-perfusion scintigraphy and ascending lower limb venography when pulmonary angiography is not available. The aim of this study is to compare color Doppler ultrasound against ascending venography in the evaluation of the lower limb deep vein system in patients with clinical suspicion of pulmonary embolism, with special attention to calf veins. We prospectively studied 30 patients with clinical suspicion of pulmonary embolism in whom a color Doppler ultrasound and venogram were performed with no more than a 3-h interval between both procedures. The diagnostic criteria was that of loss of venous compressibility. The 'color' ability was used to identify artery from vein. Out of 15 patients in whom a venogram proved positive (50%), 9 had isolated calf vein thrombosis (60%). In 5 patients, the color Doppler ultrasound of the calf was considered inconclusive. Overall sensitivity was 53%, specificity 100%, positive predictive value 100%, and negative predictive value 68%. In the femoropopliteal system, sensitivity was 83% and specificity 100%. Considering all patients, sensitivity in the calf system was 40%. Excluding the 5 patients who were difficult to assess, sensitivity increased to 60%. In conclusion, color Doppler ultrasound is not as sensitive as venography in dealing with patients with clinical suspicion of pulmonary embolism, due to its low sensitivity in the calf system when distal thrombi need to be excluded. However, a reasonable alternative is to begin by performing a compression ultrasonography of the femoropopliteal system. Color Doppler ultrasonography of the calf system represents a rarely sensitive and arduous task and does not seem justifiable in this type of patient.(ABSTRACT TRUNCATED AT 250 WORDS)

Comparison of ultrasound and blood pool scintigraphy in the diagnosis of lower limb deep venous thrombosis

We report a prospective, blinded comparison of compression ultrasound (US) and Tc-99m erythrocyte-labelled venous blood pool scintigraphy (BPS) in patients presenting with symptoms of deep venous thrombosis (DVT). Contrast venography (CV) was used as the gold standard. Ninety-eight lower limbs of 76 patients were examined. DVT was present at CV in 38 of 98 limbs and was isolated to the calf veins in eight. Sensitivity and specificity of ultrasound for femoropopliteal thrombus were 81.5% and 96% and of venous blood pool scintigraphy were 55% and 96%. For deep venous thrombosis in the whole limb sensitivity and specificity of ultrasound were 74% and 90% and of venous blood pool scintigraphy were 61% and 88%. In the calf sensitivity and specificity of US were 61% and 94% and of venous blood pool scintigraphy were 61% and 89%. Excluding equivocal venous blood pool scintigraphy results, the predictive values of a positive and negative venous blood pool scintigraphy study for the whole limb were 84% and 86%. The predictive values of a positive and negative ultrasound where the examination was adequate were 82% and 86%. US is a more sensitive alternative to CV than BPS for femoropopliteal DVT. When neither US nor CV can be performed, BPS remains a useful initial test for DVT, provided it is unequivocally positive or negative.

Limitations of compression ultrasound for the detection of symptomless postoperative deep vein thrombosis

Compression ultrasonography is regarded as the non-invasive gold-standard to detect deep vein thrombosis (DVT) in patients presenting with symptoms. However, its use as a screening method in symptom-free postoperative patients at high risk of developing DVT remains controversial. In 100 consecutive patients who had undergone craniotomy, we compared the results of bilateral compression ultrasonic measurements of the results of bilateral compression ultrasonic measurements of the entire legs with the outcomes of contrast venography. Proximal DVT was detected in 13 patients, 5 of whom also had an abnormal ultrasonic result (sensitivity 38%, 95% CI 8-69%). Only 5 of the 9 patients with an abnormal ultrasound result for the proximal veins had proximal DVT (positive predictive value, 56%, 18-94%). Calf sonograms were evaluable in 71 of the 91 patients with bilaterally normal ultrasound results for the proximal veins. Of the 16 patients with calf DVT, ultrasound was abnormal in 8 (sensitivity 50%, 25-75%). Overall, ultrasound detected 13 of the 26 patients with proximal or isolated calf DVT (sensitivity 50%, 29-71%). The positive predictive value for the whole leg examination was 41% (24-60%). Most thrombi missed by ultrasound were non-occlusive and smaller than 5 cm. We conclude that compression ultrasound is not useful for screening for DVT in symptom-free postoperative high-risk patients.

A comprehensive review of vascular ultrasound for intensivists

Ultrasound has an increasingly important role in evaluation of the vascular system. Ultrasound is especially useful for intensive care patients because of the frequency of vascular complications developing in the ICU setting, as well as the ability of ultrasound to be performed at the patient's bedside. Ultrasound is the method of choice for evaluation of deep vein thromboembolic disease of the lower extremity in all patients; it demonstrates excellent sensitivity and specificity for this condition. It should also be the initial method of evaluation of upper extremity deep vein thrombosis. However, ultrasound may be limited in this assessment due to lack of reliably demonstrating the central subclavian and innominate veins, and therefore may be inadequate for evaluation of malfunctioning central venous catheters. Ultrasound can reliably identify and potentially be used to treat arterial complications of arterial catheterization, such as pseudoaneurysms. Similarly, ultrasound is accurate in the diagnosis of the presence of abdominal aortic aneurysm, and ultrasound can be used to assess carotid and lower extremity arteries noninvasively. Finally, ultrasound is useful for evaluation of hemodialysis fistulas and vascular complications of transplants.

Detection of deep venous thrombosis by magnetic resonance imaging

OBJECTIVE

To determine the accuracy of gradient recalled echo magnetic resonance imaging in assessing deep venous thrombosis.

DESIGN

This is a retrospective review of a prospective clinical experience in 216 consecutive patients studied using gradient recalled echo magnetic resonance imaging. Sixteen patients were unavailable for follow-up and 1 study was technically suboptimal, leaving 199 studies as the basis of this report.

RESULTS

In 79 cases with confirmatory venography (n = 54), ultrasound (n = 16, thigh veins only), or computed tomography (n = 9, pelvic veins only), magnetic resonance imaging was 97 percent sensitive, 95 percent specific, and 96 percent accurate. Including cases that were normal by magnetic resonance imaging, not anticoagulated, and with uneventful follow-up as true normal cases, the corresponding sensitivity, specificity, and accuracy of magnetic resonance imaging were as follows: 97 percent, 98 percent, and 97 percent.

CONCLUSION

Magnetic resonance imaging, using gradient recalled echo acquisitions, is capable of accurately diagnosing acute deep venous thrombosis.

Asymptomatic deep venous thrombosis in the calf: accuracy and limitations of ultrasonography as a screening test after total knee arthroplasty

Patients who have recently undergone total knee arthroplasty are at high risk of developing deep venous thrombosis (DVT) in the calf. The clinical diagnosis of DVT is difficult in these patients owing to recent operation. A combination of compression ultrasonography (US) and colour flow imaging was used as a screening method of asymptomatic DVT in 51 patients who had undergone total knee replacement surgery. Both limbs were examined by US from the common femoral vein to the ankle approximately 7 days after operation and the results were compared with bilateral venography. 12 patients (24%) developed infrapopliteal DVT on the operated side, in two cases the thrombosis extended to the lower part of popliteal vein. One patient had bilateral thrombosis. US showed sensitivity of 77%, specificity of 96% and overall accuracy of 93%. US seems to be a useful screening method for DVT after knee replacement operation.

Insensitivity of color Doppler flow imaging for detection of acute calf deep venous thrombosis in asymptomatic postoperative patients

PURPOSE

Although color Doppler flow imaging (CDFI) has been shown to accurately depict calf vein thrombosis in symptomatic patients, this technique has not been proved accurate for detection of calf vein thrombosis in a population restricted to asymptomatic postoperative patients.

PATIENTS AND METHODS

To evaluate the accuracy of CDFI in asymptomatic postoperative patients, both CDFI and contrast venography were performed on 78 limbs of 76 patients without symptoms of deep venous thrombosis (DVT) who had undergone either hip or knee replacement. CDFI and venographic examination were interpreted blindly with respect to the results of the other modality or clinical findings. Venography was the standard for comparison of results.

RESULTS

Fifty-six percent of CDFI examinations of the calf vein were technically adequate. The remaining studies were compromised technically by limb swelling and/or obesity. For the technically adequate CDFI studies, calf vein thrombosis was detected in eight of 10 patients. Calculated sensitivity in this cohort was 80%, and specificity was 97%. The sensitivity of CDFI for acute calf DVT in all patients, regardless of image quality, was 42%.

CONCLUSION

These observations suggest that state-of-the-art CDFI is not an accurate examination for acute calf vein DVT in asymptomatic postoperative patients. CDFI is associated with a high rate of technically compromised studies and relatively low sensitivity in studies that are deemed technically satisfactory. These observations do not preclude the use of CDFI in postoperative patients for detection of thrombus extension into the popliteal vein or for detecting thrombosis of more proximal lower extremity veins.