Real-time ultrasound in the diagnosis of acute deep venous thrombosis of the lower extremity

Deep Vein Thrombosis in Intravenous Drug Users: An Invisible Global Health Burden

The prevalence of intravenous drug use has increased in the past decade and it represents an important risk factor for deep vein thrombosis. Intravenous drug use is a global problem, with the main culprit being heroin. Peer pressure and poverty in high-risk groups such as sex workers, females, and young adults raise the risk of intravenous drug use, which expresses itself in the form of venous thromboembolism eventually. Deep vein thrombosis typically manifests itself eight years after the initial intravenous drug administration, rendering it a silent killer. Aiming to review and summarize existing articles in this context, we performed an exhaustive literature search online on PubMed and Google Scholar indexes using the keywords "Deep Venous Thrombosis (DVT)" and "Intravenous Drug Users (IVDU)." English articles that addressed epidemiology, pathogenesis, clinical manifestations, diagnosis, differential diagnosis, management, and outcomes of DVT, including those in IVDU, were selected and analyzed. The pathogenesis of DVT development in IVDU is mainly attributed to the interplay of trauma to the vessel by repeated injection and the injected drug itself. The right-sided femoral vein is the most common vein affected. Prevalent clinical presentations include local pain, swelling, and redness with typical systemic symptoms including fever, cough, dyspnea, and chest pain on top of addiction features. There appeared to be a delay in reporting symptoms, which was most likely due to the social stigma attached to IVDU. There are over 50 conditions that present with swollen and painful limbs comparable to DVT in IVDU, making precise diagnosis critical for timely treatment. Venous ultrasound is the method of choice for diagnosing DVT. Extended anticoagulant therapy with low-molecular-weight heparin combined with warfarin is the recommended treatment. Intravenous drug abusers having DVT are affected by multiple complications and poorer outcomes such as slower recovery, recurrent venous thromboembolism (VTE), and a longer hospital stay, which put them at higher risk of morbidity, mortality, reduced productivity, and economic burden.

Incremental value of compression ultrasound sonography in the emergency department

The quick evaluation of venous thromboembolism is a key point of modern medicine since the delayed diagnosis is associated with a worse prognosis. Venous ultrasound (VU) is a sensitive and rapidly performed test in cases of suspected deep venous thrombosis. Various protocols have been proposed for its execution, such as the study of the whole deep venous circulation of the lower limb or the analysis of the femoral-popliteal area. The aim is to detect a vessel thrombus and the most sensitive element is the non-compressibility with the probe. Initially, the thrombus is hypoechogenic and adherent to the vessel; later, it tends to organize and recanalize. Usually, in the early stages, the risk of embolism is higher. The role of studying the iliac axis and calf veins is still uncertain. VU is not useful for assessing response to anticoagulation therapy and it is unclear whether the persistence of thrombotic abnormalities can guide on a possible prolongation of therapy.

Unexpected Populations for Deep Vein Thrombosis: Presentation in an Endurance Athlete

This case presents an athletic 40-year-old female marathon runner who presented with a headache secondary to dural venous sinus thrombosis and right calf deep vein thrombosis (DVT). Though this is outside of the typical image we portray of a common DVT patient, athletes too experience hypercoagulable risk factors and medical issues, just as their less in-shape peers. This patient's history of oral contraceptive use, Lynch syndrome, colon cancer, and pregnancy indicates potential risk factors for DVT. Even without these though, it is important to note that every endurance athlete experiences hemoconcentration, dehydration, and inflammation during exercise, training, and competition events. This case demonstrates the need for an increased index of suspicion in endurance athletes. The case exemplifies an all-too-frequent occurrence of allowing our differential to be skewed away from potentially life-threatening conditions like DVT, and their thrombotic sequelae, because of the "textbook population" descriptions of a given disease state. We hope this case will shed needed light on the phenomenon and lead to more controlled research on the probability and pathophysiology for thrombotic events in this broadened population so that its incidence and prevalence in endurance athletes can be accurately reported in the literature.

Diagnosis of deep vein thrombosis of the lower extremity: a systematic review and meta-analysis of test accuracy

Deep vein thrombosis (DVT) of the lower extremities can be associated with significant morbidity and may progress to pulmonary embolism and postthrombotic syndrome. Early diagnosis and treatment are important to minimize the risk of these complications. We systematically reviewed the accuracy of diagnostic tests for first-episode and recurrent DVT of the lower extremities, including proximal compression ultrasonography (US), whole leg US, serial US, and high-sensitivity quantitative D-dimer assays. We searched Cochrane Central, MEDLINE, and EMBASE for eligible studies, reference lists of relevant reviews, registered trials, and relevant conference proceedings. Two investigators screened and abstracted data. Risk of bias was assessed using Quality Assessment of Diagnostic Accuracy Studies-2 and certainty of evidence using the Grading of Recommendations Assessment, Development and Evaluation framework. We pooled estimates of sensitivity and specificity. The review included 43 studies. For any suspected DVT, the pooled estimates for sensitivity and specificity of proximal compression US were 90.1% (95% confidence interval [CI], 86.5-92.8) and 98.5% (95% CI, 97.6-99.1), respectively. For whole-leg US, pooled estimates were 94.0% (95% CI, 91.3-95.9) and 97.3% (95% CI, 94.8-98.6); for serial US pooled estimates were 97.9% (95% CI, 96.0-98.9) and 99.8% (95% CI, 99.3-99.9). For D-dimer, pooled estimates were 96.1% (95% CI, 92.6-98.0) and 35.7% (95% CI, 29.5-42.4). Recurrent DVT studies were not pooled. Certainty of evidence varied from low to high. This systematic review of current diagnostic tests for DVT of the lower extremities provides accuracy estimates. The tests are evaluated when performed in a stand-alone fashion, and in a diagnostic pathway. The pretest probability of DVT often assessed by a clinical decision rule will influence how, together with sensitivity and specificity estimates, patients will be managed.

Endovascular Treatment for Lower Extremity Deep Vein Thrombosis: An Overview

Lower extremity deep vein thrombosis (DVT) is a serious medical condition that can result in local pain and gait disturbance. DVT progression can also lead to death or major disability as a result of pulmonary embolism, postthrombotic syndrome, or limb amputation. However, early thrombus removal can rapidly relieve symptoms and prevent disease progression. Various endovascular procedures have been developed in the recent years to treat DVT, and endovascular treatment has been established as one of the major therapeutic methods to treat lower extremity DVT. However, the treatment of lower extremity DVT varies according to the disease duration, location of affected vessels, and the presence of symptoms. This article reviews and discusses effective endovascular treatment methods for lower extremity DVT.

Neutrophil-Lymphocyte Ratio as a Predictor of Venous Thromboembolism after Total Knee Replacement

Venous thromboembolism (VTE) is a potentially serious complication after total knee replacement (TKR), and recent guideline recommends thromboprophylaxis for VTE after TKR. The neutrophil-lymphocyte ratio (NLR) has emerged as a simple and new prognostic biomarker for several cardiovascular diseases. This study was performed to investigate the precise incidence of postoperative VTE and the role of NLR for predicting VTE in patients receiving thromboprophylaxis after TKR. We retrospectively enrolled 264 patients undergoing TKR who underwent routine screening enhanced pulmonary artery and lower extremity venography computed tomography (CT) scan within 7 postoperative days. Biochemical tests were performed within 2 weeks prior to surgery, and the NLR was defined as the absolute neutrophil count in peripheral blood divided by lymphocyte count. All patients received thromboprophylaxis with enoxaparin postoperatively. Of 264 patients, 102 (38.6%) were diagnosed with deep vein thrombosis (DVT) or pulmonary embolism on CT scan. Preoperative NLR was significantly higher in patients with postoperative VTE compared with that in patients without VTE (2.57 ± 1.59 vs. 2.11 ± 1.10, p = 0.011). Receiver operating characteristic curve analysis showed that a preoperative NLR of 1.90 was the best cutoff value for the prediction of postoperative VTE (sensitivity 57.8%, specificity 55.6%, and area under curve 0.589). In the multivariate analysis, a preoperative NLR ≥1.90 was a sole independent predictor of postoperative VTE (odds ratio: 1.95, 95% computed tomography: 1.16-3.31, p = 0.013). The present study shows a higher incidence of VTE (38.6%) after TKR in patients receiving thromboprophylaxis than that reported in previous studies. Furthermore, preoperative NLR was significantly higher in patients with postoperative VTE, and a high preoperative NLR (≥1.90) was an independent predictor of VTE after TKR. NLR measurement may be a simple and useful method for the prediction of VTE in patients undergoing TKR.

American Society of Hematology 2018 guidelines for management of venous thromboembolism: diagnosis of venous thromboembolism

BACKGROUND

Modern diagnostic strategies for venous thromboembolism (VTE) incorporate pretest probability (PTP; prevalence) assessment. The ability of diagnostic tests to correctly identify or exclude VTE is influenced by VTE prevalence and test accuracy characteristics.

OBJECTIVE

These evidence-based guidelines are intended to support patients, clinicians, and health care professionals in VTE diagnosis. Diagnostic strategies were evaluated for pulmonary embolism (PE), deep vein thrombosis (DVT) of the lower and upper extremity, and recurrent VTE.

METHODS

The American Society of Hematology (ASH) formed a multidisciplinary panel including patient representatives. The McMaster University GRADE Centre completed systematic reviews up to 1 October 2017. The panel prioritized questions and outcomes and used the Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach to assess evidence and make recommendations. Test accuracy estimates and VTE population prevalence were used to model expected outcomes in diagnostic pathways. Where modeling was not feasible, management and accuracy studies were used to formulate recommendations.

RESULTS

Ten recommendations are presented, by PTP for patients with suspected PE and lower extremity DVT, and for recurrent VTE and upper extremity DVT.

CONCLUSIONS

For patients at low (unlikely) VTE risk, using D-dimer as the initial test reduces the need for diagnostic imaging. For patients at high (likely) VTE risk, imaging is warranted. For PE diagnosis, ventilation-perfusion scanning and computed tomography pulmonary angiography are the most validated tests, whereas lower or upper extremity DVT diagnosis uses ultrasonography. Research is needed on new diagnostic modalities and to validate clinical decision rules for patients with suspected recurrent VTE.

Calf Vein Thrombosis: Diagnosis and Treatment

Objective:

To demonstrate the difficulties of the clinical diagnosis of deep vein thrombosis and demonstrate the utility of ultrasound imaging as a diagnostic technique in suspected deep vein thrombosis.

Design:

Series of three case reports.

Setting:

Grondin Clinic, Calgery, Alberta, Canada.

Patients:

Three patients with symptoms suggestive of deep vein thrombosis of the calf.

Interventions:

Duplex ultrasound imaging in all patients combined with phlebography of the lower limb in one patient.

Main outcome measure:

Presence of deep vein thrombosis or soft tissue abnormalities of the lower limb on ultrasound imaging or venography.

Results:

A Baker cyst was found in one patient, an intramuscular haematoma in a further patient, both detected by ultrasound imaging, but not by venography. In the third patient a venogram failed to demonstrate deep vein thrombosis in the calf, but this was detected on ultrasound imaging.

Conclusions:

Ultrasound imaging is a valuable tool in reaching a diagnosis in patients presenting with symptoms suggesting deep vein thrombosis in the calf.

Apolipoprotein E polymorphism is associated with lower extremity deep venous thrombosis: color-flow Doppler ultrasound evaluation

Introduction

Apolipoprotein E (apoE) is a member of apolipoprotein family, and its gene polymorphisms seem to have some impact among patients with cardiovascular disease. However, its role in the lower extremity deep venous thrombosis (LEDVT) has not been well studied. The objective of this study was to investigate the potential association between APOE gene polymorphisms and LEDVT.

Materials and methods

A hospital-based case–control study was conducted in 300 patients with LEDVT by color-flow Doppler ultrasound and 300 age- and gender-matched healthy controls. Polymerase chain reaction restriction fragment length polymorphism (PCR-RFLP) assay was applied to assess the APOE gene polymorphisms.

Results

Patients with LEDVT had a significantly higher frequency of APOE E3/E4 genotype [odds ratio (OR) =1.48, 95% confidence interval (CI) = 1.05, 2.10; P = 0.03] than healthy controls. When stratifying by family history of LEDVT, it was found that patients with positive family history of LEDVT had a significantly higher frequency of APOE E3/E4 genotype (OR =1.68, 95% CI = 1.04, 0.95; P = 2.70). When stratifying by smoking status, presence of varicose veins, type 2 diabetes mellitus and any hormone administration before, no significant differences were found in any groups.

Conclusion

Our study suggested that APOE E3/E4 genotype was associated with a higher LEDVT risk. Additional studies are needed to confirm this finding.

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.

Accuracy of ultrasonography performed by critical care physicians for the diagnosis of DVT

BACKGROUND

DVT is common among critically ill patients. A rapid and accurate diagnosis is essential for patient care. We assessed the accuracy and timeliness of intensivist-performed compression ultrasonography studies (IP-CUS) for proximal lower extremity DVT (PLEDVT) by comparing results with the formal vascular study (FVS) performed by ultrasonography technicians and interpreted by radiologists.

METHODS

We conducted a multicenter, retrospective review of IP-CUS examinations performed in an ICU by pulmonary and critical care fellows and attending physicians. Patients suspected of having DVT underwent IP-CUS, using a standard two-dimensional compression ultrasonography protocol for the diagnosis of PLEDVT. The IP-CUS data were collected prospectively as part of a quality-improvement initiative. The IP-CUS interpretation was recorded and timed at the end of the examination on a standardized report form. An FVS was then ordered, and the FVS result was used as the criterion standard for calculating sensitivity and specificity. Time delays between the IP-CUS and FVS were recorded.

RESULTS

A total of 128 IP-CUS were compared with an FVS. Eighty-one percent of the IP-CUS were performed by fellows with <2 years of clinical ultrasonography experience. Prevalence of DVT was 20%. IP-CUS studies yielded a sensitivity of 86% and a specificity of 96% with a diagnostic accuracy of 95%. Median time delay between the ordering of FVS and the FVS result was 13.8 h.

CONCLUSIONS

Rapid and accurate diagnosis of proximal lower extremity DVT can be achieved by intensivists performing compression ultrasonography at the bedside.

Anatomic distribution of deep vein thrombosis in pregnancy

BACKGROUND

Prospective studies of nonpregnant patients have demonstrated that most deep vein thromboses of the lower extremity originate in the calf veins and progress proximally, but the anatomic distribution of thromboses in pregnant patients is unclear. An understanding of the anatomic distribution of deep vein thrombosis in pregnancy has important implications for optimizing diagnostic imaging protocols. We undertook this study to determine the anatomic distribution of deep vein thrombosis of the lower extremity in symptomatic pregnant patients.

METHODS

We systematically searched MEDLINE (1966 to January 2009), Embase (1980 to January 2009) and the Cochrane Library using prespecified criteria to identify articles providing objective diagnostic and anatomic information for unselected or consecutive symptomatic pregnant patients with deep vein thrombosis.

RESULTS

Six articles from an initial list of 1098 titles met the inclusion criteria. These articles provided information for 124 pregnant women with a diagnosis of deep vein thrombosis. Overall, involvement of the left leg was reported in 84 (88%) of the 96 patients for which the side affected was known, and 87 (71%) of 122 thromboses were restricted to the proximal veins without involvement of the calf veins. Among these cases of proximal deep vein thrombosis, 64% (56/87) were restricted to the iliac and/or femoral vein.

CONCLUSION

Despite a paucity of studies in this area, the results of our review suggest that the anatomic distribution of deep vein thrombosis in pregnant women differs from that for nonpregnant patients. In addition to what was previously known--that left-sided deep vein thrombosis is more common in pregnancy--we also found that proximal deep vein thrombosis restricted to the femoral or iliac veins is also more common (> 60% of cases). If confirmed by larger studies, these findings could affect our understanding of the pathophysiology and derivation of diagnostic algorithms for examination of pregnant women with suspected deep vein thrombosis.

Early Deep Vein Thrombosis: Incidence in Asian Stroke Patients

Introduction: Deep venous thrombosis (DVT) is thought to be less common in Asians than in the Caucasian population. The incidence of asymptomatic DVT in high-risk groups in the Asian population has not been well studied. While DVT incidence among Caucasian stroke patients has been extensively studied and the need for prophylaxis established, the lack of data in Asian patients leaves physicians with no firm basis for adopting prophylactic protocols in the local population. Our aim was to prospectively establish the incidence of early DVT in immobilised stroke patients in a heterogenous Asian population. Materials and Methods: We screened 44 patients with significant hemiplegia from acute stroke. Doppler ultrasound, the currently accepted method of investigation for DVT, was used to study patients on admission and at 1 week post-stroke. While there was no standard prophylactic regime in use, none of the patients received heparin and only 2 were given compression stockings. Results: The incidence of DVT at 1 week was 2.4%. Review at 1 month detected another patient with DVT, bringing the overall incidence at 1 month to 4.8%. This is lower than in Caucasian populations, but is similar to another local study on a different group of high-risk patients. Conclusion: The low incidence of early DVT in hospitalised stroke patients of Asian ethnicity does not justify routine screening for this population. Further research to validate this should ideally include a comparison test for DVT as ultrasound may have inherently lower sensitivity in an asymptomatic population. Key words: Doppler ultrasound

Sonography for Deep Venous Thrombosis

Deep venous thrombosis (DVT) is a one of the most common problems facing the clinician in medicine today. It is often asymptomatic and goes undiagnosed with potentially fatal consequences. Ultrasound has become the "gold standard" in the diagnosis of deep venous thrombosis and with proper attention to technique sensitivity of this test is approximately 97%. An understanding of anatomy, pathophysiology, and risk factors is important. Thrombus formation usually begins beneath a valve leaflet below the knee. Approximately 40% will resolve spontaneously, 40% will become organized, and 20% will propagate. Whether or not a calf vein thrombus is identified, a repeat examination in 7 to 10 days is recommended in patients with risk factors or when deep venous thrombosis is suspected. The three main risk factors for thrombus formation are age greater than 75 years, previous history of deep venous thrombosis, and underlying malignancy. Other diagnostic studies include the contrast venogram, CT or MRI venogram, Tc99m Apcitide study, and the laboratory test D-Dimer. The D-Dimer study is being used more frequently as a screening test with 99% sensitivity in detecting thrombus, whether deep venous thrombosis or pulmonary embolism. However, specificity is only approximately 50% with many conditions leading to false-positive exams. Therefore, a negative examination is useful in avoiding other diagnostic studies, but a positive one may be misleading. Conditions that can lead to a false-positive examination include, but are not limited to diabetes, pregnancy, liver disease, heart conditions, recent surgery, and some gastrointestinal diseases. Like the sonogram, two negative D-Dimer studies a week apart exclude the diagnosis of deep venous thrombosis. Compression sonography with color Doppler remains the best overall test for deep venous thrombosis. It is easy to perform, less expensive than most "high tech" studies, can be performed as a portable examination, and is highly reliable when done properly.

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.

Notions d’hémodynamique et techniques ultrasonores pour l’exploration des veines du cou et des membres

Deep venous thrombosis and venous insufficiency are now easily diagnosed with US imaging. US allows anatomic evaluation of the vessel walls and dynamic evaluation of flow velocities. Knowledge of vascular anatomy and physiology is required to interpret US data. The sensitivity of US for the diagnosis of deep venous thrombosis is up to 95% at the leg level, 98% at the popliteal level, and 100% at the femoral level with a specificity of nearly 100%. Venography is thus rarely performed. The sensitivity for the diagnosis of deep venous thrombosis at the neck level is up to 90%. Follow-up can easily be performed because of the wide availability of US.

[Venous compression ultrasonography of the lower limbs: a diagnostic tool in the hands of pneumologists]

Our objective was to study agreement between the compression ultrasound images taken in our respiratory medicine department and the duplex ultrasound images obtained by radiologists at our hospital for patients admitted to our ward with suspected diagnoses of venous thromboembolism.Seventy-eight consecutive patients admitted to our respiratory medicine ward suspected of venous thromboembolism were enrolled. Both types of images were available for all patients studied. Agreement was 90% with a Kappa coefficient of 0.81. Agreement between the two techniques was good. Therefore, compression ultrasonography is a technique that can be handled by respiratory medicine specialists for the diagnosis of venous thromboembolism.

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.

Venous duplex scanning for unilateral symptoms: when do we need a contralateral evaluation?

OBJECTIVES

Determine the need for bilateral duplex scanning (DS) in patients with unilateral symptoms of acute DVT of the leg.

DESIGN

Prospective study.

MATERIALS

One thousand, one hundred and sixty-one consecutive patients with recent unilateral symptoms of pain or swelling.

METHODS

Bilateral DS were performed and demographic data including risk factors for DVT were entered into a computerised database.

RESULTS

Of the 250 cases (22%) of acute DVT, thrombus was confined to the symptomatic limb in 80% (200/250) and to the asymptomatic limb (AL) in 5% (12/250), while bilateral DVT was found in 15% (38/250). The management was not altered by the contralateral DS findings in any patient with bilateral thrombus. Ten of the 12 cases of DVT confined to the AL were localised to the infrapopliteal level; advanced malignancy, recent joint surgery or hypercoagulability were noted in nine patients, including all those requiring treatment.

CONCLUSIONS

In the presence of unilateral symptoms of DVT, we recommend DS of the symptomatic extremity only; bilateral examination should be confined to patients with normal duplex findings in the symptomatic limb following recent joint surgery, or in the presence of advanced malignancy or hypercoagulability. Bilateral DS would therefore be required in approximately 11% of cases with unilateral symptoms of DVT.

Incidence of deep venous thrombosis associated with femoral venous catheterization

OBJECTIVE

To determine in adult medical patients the incidence of deep venous thrombosis (DVT) resulting from femoral venous catheterization (FVC).

METHODS

A prospective, observational study was performed at a 420-bed community teaching hospital. Heparin-coated 7-FR cm femoral venous catheters were inserted unilaterally into a femoral vein. Each contralateral leg served as a control site. Age, gender, number of FVC days, DVT risk factors, administration of DVT prophylaxis, and DVT formation and site were tabulated for each patient. Venous duplex sonography was performed bilaterally on each patient within 7 days of femoral venous catheter removal.

RESULTS

Catheters were placed in 29 men and 13 women. Femoral DVT was identified by venous duplex sonography in 11 (26.2%) of the FVC legs and none (0%) in the control legs. Posterior tibial and popliteal DVT was identified in both the FVC and control legs of 1 patient. DVT formation at the site of FVC insertion was highly significant (p = 0.005). There were no statistically significant associations with age (p = 0.42), gender (p = 0.73), number of DVT risk factors (p = 0.17), number of FVC days (p = 0.89), or DVT prophylaxis (p = 0.99).

CONCLUSION

Placement of femoral catheters for central venous access is associated with a significant incidence of femoral DVT as detected by venous duplex sonography criteria at the site of femoral venous catheter placement. Physicians must be aware of this risk when choosing this vascular access route for adult medical patients. Further studies to assess the relative risk for DVT anf its clinical sequelae when using the femoral vs other central venous catheter routes are indicated.

Local venous thrombosis after cardiac catheterization

Pulmonary embolism is a rare but life-threatening complication of cardiac catheterization. Underlying deep venous thrombosis (DVT) is often not detectable clinically. To determine the true incidence of DVT the authors prospectively studied 450 consecutive patients (29% women, 71% men, mean age: fifty-eight years) undergoing a diagnostic cardiac catheterization. Patients were examined clinically and by duplex sonography with a high-resolution (5 or 7.5 MHz) transducer before and twenty-four hours after catheterization before mobilization. Duplex sonography excluded complete proximal DVT in all patients. Only partial occluding thrombi (pDVT) were detected in 11 (2.4%) patients. The thrombi were always localized at the puncture site. In 2 patients a difference was found in the circumferences of the legs, but no other clinical signs of DVT were seen. With use of continuous wave (cw) Doppler sonography, only 3 of these 11 patients (27%) showed a spontaneous (s) sound. Phlebography was performed in 4/11 patients (36%). In 2 patients the diagnosis was confirmed; in 1 patient extravenous compression was assumed, and the other demonstrated a normal-appearing phlebography at the time of investigation. Logistic regression analysis yielded a 3.5 times higher risk for developing a pDVT if a venous puncture was performed in addition to arterial puncture. Furthermore a 9.8 times higher risk was found if more than one venous puncture was necessary. During the follow-up no patient developed clinical signs of pulmonary embolism. The results of this study demonstrate that DVT is a rare complication of cardiac catheterization (0/450 patients), but pDVT occurred in 2.4%. Risk factors for pDVT are the venous puncture itself and multiple puncture attempts. Clinical relevance of pDVT remains to be determined.

A prospective study comparing duplex scan and venography for diagnosis of lower-extremity deep vein thrombosis

This study was designed to compare duplex scanning with contrast venography for the diagnosis of acute deep vein thrombosis of the lower extremity, both at the femoropopliteal (above-knee) and tibioperoneal (below-knee) levels. A total of 216 patients with 220 limbs suspected of acute deep vein thrombosis underwent duplex scanning followed within 24 h by ascending venography. The two studies were interpreted independently by two physicians who were blinded to the results of the corresponding alternative study. Venography was positive for deep vein thrombosis in 44.5% of cases (98/220). Duplex scanning was inadequate at the above-knee level in two cases (0.9%) and at the below-knee level in 17 cases (7.7%). Sensitivity and specificity of duplex scanning at above-knee level were 98.7% and 100% respectively while corresponding values were 85.2% and 99.2% at below-knee level. By excluding technically inadequate duplex studies, the sensitivity at below-knee level was clearly improved (93.8%). It is concluded that with meticulous technique, duplex scanning is highly accurate in diagnosing acute deep vein thrombosis of symptomatic lower extremities, avoiding contrast venography in over 90% of the cases, even at the tibioperoneal level.

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.

Allastair B. Karmody Award. Calf vein thrombi are not a benign finding

BACKGROUND

Currently, there is no consensus in the literature regarding which patients with calf vein thrombi are at high risk for proximal propagation. This study examined patients with isolated calf vein thrombi with serial duplex scans in order to identify risk factors that would predict outcome.

PATIENTS AND METHODS

Between May 1989 and November 1994, 288 patients were identified with isolated calf vein thrombi. One hundred ninety-two of them had sequential scans performed.

RESULTS

Fifty-three (28%) of the 192 patients had propagation of their initial thrombi. The most proximal level of propagation was the popliteal vein in 11 patients, the superficial femoral vein in 5, the common femoral vein in 5, adjacent tibial or soleal veins in 24, adjacent soleal veins alone in 7, and the lesser saphenous vein in 1. Three patients whose thrombi propagated had free-floating thrombus tips in the large veins of their thighs. Symptoms, prophylaxis, and risk factor analysis comparing those patients whose thrombi propagated to those whose thrombi did not found no statistically significant prognostic value. Single or multiple calf vein thrombi did not predict propagation. Of the 23 patients treated with heparin, only 3 had thrombus propagation. None of these reached the level of the knee (including popliteal vein).

CONCLUSIONS

The natural history of distal lower extremity thrombosis does not appear to be as benign as previously believed.

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.

Evaluation of suspected deep venous thrombosis in oncologic patients

Impedance plethysmography (IPG) and duplex scanning with color flow Doppler were performed in 100 consecutive high-risk patients with clinically suspected deep venous thrombosis. Risk factors included recent surgery (< three weeks) in 23%, malignant disease in 91%, clotting abnormalities in 32%, and limited activity in 70%. Lower limb findings of either edema, calf tenderness, or both occurred in 92%. There was agreement between the two tests in 76 patients (29 positive and 47 negative). In 12 patients the IPG was positive and the duplex negative. Four of these had extensive pelvic disease, 2 had lung cancer with an obstructive profile, and 2 had heart failure, all of which are known to cause false-positive IPG results. In the other 12 patients the IPG was negative and the duplex positive; however, 3 of these patients had nonocclusive thrombi, 5 had pelvic disease, and 1 had a hemiparesis of the involved lower limb. In 15 patients (11 with positive duplex studies and 4 with negative) a venogram was obtained and confirmed the results. All patients were followed up clinically and none developed complications suggesting inaccurate duplex results. In conclusion, the IPG is of limited utility in this population with a sensitivity of 71%, specificity of 80%, and false-negative rate of 29% when duplex Doppler and clinical outcome are used as the standard. Where available, duplex Doppler should be preferred for evaluation of suspected deep venous thrombosis in patients with extensive medical disease.

Diagnosis of deep vein thrombosis

In this chapter, various tests have been discussed in the diagnosis of DVT and have been classified according to various patient categories. To summarize, the following guidelines may be of clinical use in the management of patients with suspected DVT. Acute, First Event of Suspected DVT These patients often suffer from occluding, proximal thrombi. Therefore, noninvasive tests such as CUS or IPG are most suitable for these patients. If an abnormal CUS or IPG result is found, the diagnosis is virtually proven, and this may serve as a basis to treat the patient with anticoagulants. If a normal CUS or IPG result is obtained, serial testing is indicated to detect extending calf vein thrombi or nonoccluding DVT, which becomes occlusive at follow up. Anticoagulants may be withheld safely if the test remains normal within 1 week. Acute, Recurrent Suspected DVT These patients may have residual thrombi present, which makes the noninvasive tests (CUS/IPG) less useful. However, if a normal noninvasive test was documented previous to the acute recurrent event, this test may be used. If an abnormal test result is found in the presence of a documented, normal previous-test outcome, this may serve as a basis for anticoagulant therapy. Although no formal studies have been performed to evaluate the safety of withholding anticoagulants if a normal CUS or IPG result is obtained, serial testing is likely to be adequate in these circumstances. Phlebography is the only truly evaluated approach, and this could be considered in all suspected recurrent DVT. Furthermore, contrast venography is the test of choice to discern acute from old thrombi. Asymptomatic DVT in High-Risk Patients The majority of these thrombi are mostly localized in the calf veins only and are often nonocclusive. This makes noninvasive tests unreliable for their detection. Therefore, only contrast venography should be used in this patient category.

Non-invasive detection of deep venous thrombosis: ultrasonography versus duplex scanning

In a prospective study the diagnostic value of compression ultrasonography (CUS) versus Duplex scanning (DS) in the non-invasive detection of acute femoropopliteal deep venous thrombosis (DVT) was determined. In 114 eligible patients clinically suspected of DVT of the lower extremity, compression ultrasonography and Duplex scanning were performed within 24 hours by different assessors unaware of the outcome of the other test. In 109 patients concordant results of combined compression ultrasonography and Duplex scanning were obtained and considered as a proof of the absence or presence of deep venous thrombosis and no subsequent invasive investigations were performed. In five patients compression ultrasonography and Duplex scanning were discordant and contrast venography was performed. Femoropopliteal thrombosis was present in 47 legs (41%). The sensitivity, specificity and accuracy of compression ultrasonography were 93.6, 97.0 and 95.6%, respectively, and of Duplex scanning 100, 98.5 and 99.1%, respectively. We conclude that compression ultrasonography and Duplex scanning are methods with comparably high accuracy. Because of its availability, accuracy, cost-effectiveness and simplicity we recommend compression ultrasonography as the primary diagnostic test in the detection of deep venous thrombosis.

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.

Noninvasive imaging of the lower extremity for deep venous thrombosis

Noninvasive imaging for LE DVT has advanced remarkably in the past decade. Currently, IPG and ultrasound techniques (RTU and DS) have been proven to be quick, accurate, relatively inexpensive, and widely available methods for detecting proximal LE DVT and can be used as the initial diagnostic studies in many settings. Color-flow Doppler ultrasound studies may be more accurate than other ultrasound techniques in diagnosing calf DVT and in differentiating acute from chronic LE DVTs, though this bears further review. Many concerns remain regarding noninvasive LE DVT imaging, including: The accuracy of the above studies in nonreferral centers. The need for and optimal frequency of follow-up studies to detect clots that propagate proximally. The optimal noninvasive techniques for imaging in the setting of recurrent DVT and other specialized settings (e.g., high-risk patients).

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.

Heparin Study in Internal Medicine (HESIM): design and preliminary results

The Heparin Study in Internal Medicine (HESIM) compares the efficacy and safety of an unfractionated (UF) heparin with a low molecular weight (LMW) heparin (CY 216 D) for prevention of proximal deep vein thrombosis (DVT) and pulmonary embolism (PE) in medical inpatients with a high risk for development of thromboembolism. Patients are randomized and receive three times daily 5000 IU UF heparin or once daily 3100 IU LMW heparin and two placebo injections subcutaneously for 10 days. All patients are screened for the presence of proximal DVT at day 1 and 10 by real-time B-mode compression sonography and for PE by repeated clinical examinations. Perfusion scintigraphy is used for confirmation of the clinical diagnosis of PE. The study protocol includes a stratified randomization of patients on admission to the hospital according to one of the following main diagnoses: malignant disease, cardiovascular disease, bronchopulmonary disease, neurologic disease, and other diseases. The present study may serve as a model for further clinical trials in medical inpatients using the biometric approach of statistical analysis for proving equivalence of drug efficacy, and to adopt less sensitive but noninvasive methods for the detection of primary endpoints.

Prospective randomized trial of warfarin and intermittent pneumatic leg compression as prophylaxis for postoperative deep venous thrombosis in major urological surgery

Postoperative deep venous thrombosis and pulmonary embolus remain a major source of morbidity and mortality for the urological surgery patient. We report the results of the first 100 patients in a prospective, randomized trial of low dose warfarin and intermittent pneumatic leg compression for deep venous thrombosis prophylaxis. All patients underwent preoperative and postoperative real-time ultrasound imaging and Doppler flow studies of the popliteal, femoral and iliac veins for the evaluation of deep venous thrombosis. Our results indicate that low dose warfarin is as effective as intermittent pneumatic leg compression for prophylaxis of deep venous thrombosis. Low dose warfarin can be used effectively without any significant bleeding complications. We recommend the use of low dose warfarin as an alternative to intermittent pneumatic leg compression for deep venous thrombosis prophylaxis of the urological patient undergoing a major urological operation.