Limited B-mode venous imaging versus complete color-flow duplex venous scanning for detection of proximal deep venous thrombosis

Competencies for Point-of-care Ultrasonography in ICU: An ISCCM Expert Panel Practice Recommendation

How to cite this article: Srinivasan S, Kumar PG, Govil D, Gupta S, Kumar V, Pichamuthu K, et al. Competencies for Point-of-care Ultrasonography in ICU: An ISCCM Expert Panel Practice Recommendation. Indian J Crit Care Med 2022;26(S2):S7-S12.

Distribution of Lower Extremity Deep Vein Thrombosis and Implications for Limited Compression Ultrasound Examinations

BACKGROUND

Limited compression bedside ultrasonography (LCUS) including two-point, three-point, and extended compression examinations have become increasingly popular among emergency physicians to assess for lower extremity deep venous thrombosis (DVT).

OBJECTIVE

Our objective in this study was to determine the prevalence and distribution of lower extremity DVT in sites identified by complete duplex ultrasonography (CDUS) that may potentially be missed using limited compression ultrasonography techniques.

METHODS

This was a retrospective, multicenter study conducted at 12 hospitals within the Northwell Health system over a span of 4 years. Study participants (emergency department patients) underwent CDUS to assess for possible DVT. Images were reviewed and interpreted by radiologists and vascular surgeons at each of the participating institutions.

RESULTS

A total of 42,487 CDUS examinations were performed, of which 3383 were positive for DVT. DVTs were deemed to be acute in 2664 (79%) and chronic in the remaining 21% on the basis of comparison with previous studies and appearance of the vein. Of the acute DVTs, 136 (5.1%) were confined to the common femoral vein, 116 (4.4%) to the femoral vein, 8 (0.3%) to deep femoral vein, 213 (8.0%) to popliteal vein, and 934 (35.1) to calf veins alone.

CONCLUSIONS

In our study, a significant number of DVTs were identified in sites that may have been potentially missed on LCUS examinations, thereby supporting the use of complete duplex ultrasonography when available.

Non-invasive imaging techniques for the differentiation of acute and chronic thrombosis

Thrombosis is the localized clotting of blood that can occur in both the arterial and venous circulation. It is a key factor in the pathogenesis of acute coronary syndrome, myocardial infarction and stroke and the primary cause of deep vein thrombosis and pulmonary embolism. Rapid and accurate diagnosis of thrombotic episodes is crucial in reducing the morbidity and potential mortality associated with arterial and venous thrombotic disorders by allowing early targeted therapeutic interventions. From a clinical perspective the ability to accurately assess the age and composition of thrombus is highly desirable given that anticoagulation and, in particular, fibrinolytic therapies are more effective in treating acute rather than chronic thrombosis. While there are no imaging tests used in routine clinical practice that can reliably determine the age of thrombus and differentiate between acute and chronic thrombosis there are several emerging non-invasive techniques that can provide an indication of the age of a thrombus depending on its location in the body. Examples of techniques developed for venous thrombosis include Doppler imaging with venous duplex ultrasonography, ultrasound B-mode imaging integrated with IER (intrinsic mode functions-based echogenicity ratio), elastography, scintigraphy imaging with ^99mTc-recombinant tissue plasminogen activator (^99mTc-rt-PA), and magnetic resonance direct thrombus imaging (MDRTI). Magnetic resonance imaging (MRI) has been used to noninvasively detect and differentiate acute and chronic arterial and venous thrombosis. These methods have limitations that need further investigation to enable cost-effective and clinically relevant treatment practices to be established in the future. This review will discuss the difference between acute and chronic thrombosis and the role of non-invasive imaging techniques in discriminating between the two.

Differential Diagnosis of Acute Calf Pain and Swelling with Emergency Ultrasound

Acute calf pain and swelling are common causes of emergency department attendance. Differential diagnoses may mimic each other causing confusion and uncertainty in management. With emergency ultrasound, most of the differential diagnoses for acute calf pain and swelling can be identified with confidence. We present two cases of calf pain and swelling utilising ultrasound to clarify the diagnosis.

Effect of Focused Bedside Ultrasonography in Hypotensive Patients on the Clinical Decision of Emergency Physicians

We assessed the effect of focused point of care ultrasound (POCUS) used for critical nontraumatic hypotensive patients presenting to the emergency department of our hospital on the clinical decisions of the physicians and whether it led to the modification of the treatment modality. This prospective clinical study was conducted at the Emergency Department of Antalya Training and Research Hospital. Nontraumatic patients aged 18 and older who presented to our emergency department and whose systolic blood pressure was <100 mmHg or shock index (heart rate/systolic blood pressure) was >1 were included in the study. While the most probable preliminary diagnosis established by the physician before POCUS was consistent with the definitive diagnosis in 60.6% (n = 109) of 180 patients included in the study, it was consistent with the definitive diagnosis in 85.0% (n = 153) of the patients after POCUS (p < 0.001). POCUS performed for critical hypotensive patients presenting to the emergency department is an appropriate diagnostic tool that can be used to enable the physicians to make the accurate preliminary diagnosis and start the appropriate treatment in a short time.

Mistakes and Pitfalls Associated with Two-Point Compression Ultrasound for Deep Vein Thrombosis

Introduction

Two-point compression ultrasound is purportedly a simple and accurate means to diagnose proximal lower extremity deep vein thrombosis (DVT), but the pitfalls of this technique have not been fully elucidated. The objective of this study is to determine the accuracy of emergency medicine resident-performed two-point compression ultrasound, and to determine what technical errors are commonly made by novice ultrasonographers using this technique.

Methods

This was a prospective diagnostic test assessment of a convenience sample of adult emergency department (ED) patients suspected of having a lower extremity DVT. After brief training on the technique, residents performed two-point compression ultrasounds on enrolled patients. Subsequently a radiology department ultrasound was performed and used as the gold standard. Residents were instructed to save videos of their ultrasounds for technical analysis.

Results

Overall, 288 two-point compression ultrasound studies were performed. There were 28 cases that were deemed to be positive for DVT by radiology ultrasound. Among these 28, 16 were identified by the residents with two-point compression. Among the 260 cases deemed to be negative for DVT by radiology ultrasound, 10 were thought to be positive by the residents using two-point compression. This led to a sensitivity of 57.1% (95% CI [38.8–75.5]) and a specificity of 96.1% (95% CI [93.8–98.5]) for resident-performed two-point compression ultrasound. This corresponds to a positive predictive value of 61.5% (95% CI [42.8–80.2]) and a negative predictive value of 95.4% (95% CI [92.9–98.0]). The positive likelihood ratio is 14.9 (95% CI [7.5–29.5]) and the negative likelihood ratio is 0.45 (95% CI [0.29–0.68]). Video analysis revealed that in four cases the resident did not identify a DVT because the thrombus was isolated to the superior femoral vein (SFV), which is not evaluated by two-point compression. Moreover, the video analysis revealed that the most common mistake made by the residents was inadequate visualization of the popliteal vein.

Conclusion

Two-point compression ultrasound does not identify isolated SFV thrombi, which reduces its sensitivity. Moreover, this technique may be more difficult than previously reported, in part because novice ultrasonographers have difficulty properly assessing the popliteal vein.

Point-of-Care Ultrasound for a Deep Venous Thrombosis

Patients presenting to the emergency department with lower extremity symptoms suggestive of venous thromboembolic disease require a diagnostic evaluation. Although contrast venography was the diagnostic standard, this has largely been replaced by duplex ultrasound as the first-line imaging modality. This review presents a summary of the literature on the evolution and performance of B-mode point-of-care compression ultrasound as an alternative to duplex ultrasound evaluation. The 2-point compression and 2-region compression techniques are described. The limitations of point-of-care ultrasound of the lower extremity as a diagnostic modality for this disease entity, the role of a D-dimer assay in the emergency department evaluation and future directions for this diagnostic modality are discussed.

The CORE scan: concentrated overview of resuscitative efforts

Critically ill patients require rapid, accurate assessments and appropriate therapeutic interventions to maximize their chances of recovery. Often the cause of a patient's decompensation is not readily apparent based solely on history and physical examination findings. The Concentrated Overview of Resuscitative Efforts (CORE scan) is a compilation of targeted bedside ultrasound exams that should be performed during the assessment and management of critically ill patients. The CORE scan can be used to help make critical diagnoses and guide resuscitation efforts in patients with undifferentiated deterioration.

Bedside ultrasound in resuscitation and the rapid ultrasound in shock protocol

Assessment of hemodynamic status in a shock state remains a challenging issue in Emergency Medicine and Critical Care. As the use of invasive hemodynamic monitoring declines, bedside-focused ultrasound has become a valuable tool in the evaluation and management of patients in shock. No longer a means to simply evaluate organ anatomy, ultrasound has expanded to become a rapid and noninvasive method for the assessment of patient physiology. Clinicians caring for critical patients should strongly consider integrating ultrasound into their resuscitation pathways.

The accuracy of limited B-mode compression technique in diagnosing deep venous thrombosis in lower extremities

BACKGROUND

Deep vein thrombosis (DVT) is prevalent in the emergency departments. Nearly 60% of them may lead to pulmonary embolism. A complete color-flow duplex ultrasound (CFDU), performed by the radiologists, is the most common diagnostic method used to detect DVT. A limited B-mode compression technique (BMCT) can also be useful for the emergency specialists visiting suspicious cases.

OBJECTIVES

The purpose of this study was to compare the sensitivity, specificity, and accuracy of a BMCT done by emergency medicine residents with that of a CFDU in diagnosing the proximal DVT of lower extremities.

METHODS

This prospective study was conducted on 74 patients (41 men and 33 women) presenting with painful and swollen lower limbs in the emergency department of Imam Khomeini Hospital. First, the affected lower extremity was examined by a BMCT carried out by one of the 2 emergency medicine residents. Then, the CFDU was performed by a radiologist blinded to the results of the BMCT. The sensitivity, specificity, and accuracy of the BMCT were compared with that of the CFDU as a gold standard.

RESULTS

The mean age of the patients was 55.16 ± 17.4 years. Positive results were reported in 35 patients (47.3%) using the 2 tests. Compared with CFDU, BMCT had a sensitivity, specificity, accuracy, positive predictive values, and negative predictive values of 100%.

CONCLUSION

These findings suggest that BMCT performed by the emergency medicine specialists to diagnose proximal DVT of lower extremities is not only an acceptable method but also less time-consuming when compared with CFDU.

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.

The RUSH exam: Rapid Ultrasound in SHock in the evaluation of the critically lll

The RUSH exam (Rapid Ultrasound in SHock examination), presented in this article, represents a comprehensive algorithm for the integration of bedside ultrasound into the care of the patient in shock. By focusing on a stepwise evaluation of the shock patient defined here as "Pump, Tank, and Pipes," clinicians will gain crucial anatomic and physiologic data to better care for these patients.

Venothromboembolism

This article focuses on the clinical presentation, diagnosis, and management of veno-thromboembolism, including deep venous thrombosis (DVT) and pulmonary embolism (PE), from the perspective of the emergency physician. The discussion is divided into two sections: DVT and PE. Because veno-thromboembolism is a continuum, certain aspects, such as background, incidence, the use of D dimer, and anticoagulation of both DVT and PE, are discussed together. Heavier emphasis is placed on topics germane to the emergency physician, and considerations for special populations are reviewed.

Ultrasound in the detection of venous thromboembolism

Venous thrombosis is a common disease process leading to tens of thousands of deaths per year. Despite prophylactic efforts, venous thromboembolic disease is a common and serious complication in critical care patients. Difficulty and delay in obtaining diagnostic imaging studies to rule out deep venous thrombosis is exacerbated by increased susceptibility that critically ill patients have to thromboembolism. Lower extremity venous ultrasound use by clinicians has been well studied and has proven both reliable and efficient. Evaluation of the upper extremities can be more challenging and requires a higher degree of technical skill. However, both can be integrated into an overall scheme of prevention, screening, and rapid diagnosis of thromboembolic disease and its complications. This article delves into available literature and describes performance of both applications in a critical care setting.

Lower extremity deep venous thrombosis: vascular laboratory quality assurance without correlation between ultrasound and venography

Venography is rarely available for comparison with ultrasonography (US) as a means for quality assurance (QA) in the detection of lower extremity venous thrombosis. New QA methods must be implemented. We compared results of multiple serial studies performed in the same extremity as a QA indicator. From a 3-year sample of close to 9,000 venous tests, we obtained a subset of 44 patients who had 331 tests in 71 lower extremities throughout the years. A positive or negative study preceded or followed by another positive or negative study was considered as a confirmed study. A negative or positive study not preceded or followed by a negative or positive study was considered as unconfirmed. Explanations were then sought to explain unconfirmed results. There were 169 (51%) and 124 (37%) confirmed positive and negative studies, respectively, and 13 (4%) and 25 (8%) unconfirmed positive and negative studies, respectively. Of the 13 unconfirmed positive tests, 2 were preceded by negative tests, 3 were preceded and followed by negative tests, and 8 were followed by negative tests. Of these 13 tests, 4 documented extensive venous thrombosis. Of the 25 unconfirmed negative tests, 11 followed treatment for venous thrombosis, 6 had recurrent thrombosis with intermittent lysis, and 8 were followed by positive tests. Considering the low probability of extensive thrombosis being a false-positive test, positive predictive value was 95% (173/182). Excluding 11 negative tests following treatment for venous thrombosis, negative predictive value was 90% (124/138) and accuracy was 93% (297/320). US versus US and literature US versus venography comparisons of these statistics were similar.

Ultrasound diagnosis of deep venous thrombosis

The ultrasound diagnosis of deep venous thrombosis by an emergency physician is occurring with increased frequency. The examination is simple to perform and, when combined with a clinical pretest probability or D-dimer, can aid in the rapid disposition ofa patient with lower extremity pain and swelling. The technique and findings of the limited lower extremity ultrasound and the data to support its use in the emergency department are discussed.

Real-time B-mode ultrasound in the ED saves time in the diagnosis of deep vein thrombosis (DVT)

We hypothesize that EPs can decrease the time to disposition when performing examinations for deep venous thrombosis (DVT) compared with disposition times using imaging specialists (IS). We performed a prospective, single-blind observational study at an academic ED over the course of 1 year. Patients were enrolled based on study physician availability. EPs ordered the corroborative ultrasound, then performed their own examination. EPs recorded patient triage time, ED results, and disposition times for both EP and IS departments. One hundred fifty-six patients were enrolled. Thirty-four (22%) were diagnosed with a DVT. Mean time from triage to EP disposition was 95 minutes and mean time from triage to radiology disposition was 220 minutes. The difference of 125 minutes was statistically significant (P <.0001). EPs and ISs had excellent agreement (kappa = 0.9). Compression ultrasound performed by EPs resulted in a significant decreased time to disposition. Agreement with ISs was excellent.

Resident-performed compression ultrasonography for the detection of proximal deep vein thrombosis: fast and accurate

OBJECTIVES

To assess whether emergency medicine residents (EMRs) could quickly perform accurate compression ultrasonography (CUS) for the detection of proximal lower extremity deep vein thromboses (PLEDVTs) with minimal training.

METHODS

A prospective, observational study using a convenience sample of patients presenting with signs and/or symptoms for PLEDVT. Vascular laboratory and department of radiology studies were considered the criterion standard. CUS of the femoral vessels was performed. Incompressibility or visualized thrombus was considered "positive."

RESULTS

Eight residents with limited ultrasound (US) experience and no prior experience with deep vein thrombosis (DVT) US volunteered to participate in this study, enrolling 72 patients. Their average scan time was 11.7 minutes (95% CI = 9.4 to 14). There were 23 true positives, 4 false positives, 45 true negatives, and 0 false negatives. The test characteristics for PLEDVT gave a sensitivity of 100% (95% CI = 82.2 to 100) and a specificity of 91.8% (95% CI = 79.5 to 97.4).

CONCLUSION

Emergency medicine residents with limited US experience were able to quickly perform CUS after minimal training for the detection of PLEDVT in a select group of patients.

The diagnosis of lower extremity deep venous thrombosis

The diagnosis of lower extremity deep venous thrombosis (DVT) is critical to emergency physicians because of the risk of pulmonary embolism. This article reviews the diagnostic modalities available for patients with suspected lower extremity DVT. The use of compression ultrasonography and the recent advances in the D-dimer assays are emphasized. A clinical algorithm that utilizes a non invasive approach to this potentially life threatening disease is presented.

Emergency Department compression ultrasound to diagnose proximal deep vein thrombosis

Emergency Department (ED) patients with suspected deep vein thrombosis (DVT) require an objective vascular study such as ultrasound (US) to confirm the diagnosis prior to treatment or disposition. A simple compression US test of the common femoral vein and popliteal vein reliably detects proximal DVT in symptomatic patients. Application of compression US in the ED by Emergency Physicians (EPs) has been tested in a single previous study. We evaluated the ability of ED compression US, performed by EPs, to diagnose proximal DVT as compared to duplex US performed in a vascular laboratory. A prospective, observational study was conducted on a convenience sample of patients presenting to an ED with lower extremity symptoms and signs suggestive of DVT. Patients with a history of DVT in the symptomatic extremity were excluded. Final diagnosis of DVT was made by color-flow duplex US performed in a vascular laboratory. ED compression US was performed by one of six EP sonographers. In compression US, DVT was diagnosed by the inability to compress the common femoral vein or popliteal vein. The examination was considered indeterminate if the veins could not be clearly identified or compressibility was equivocal. For statistical analysis, an indeterminate examination was considered positive. In those cases where ED compression US was discordant with duplex US, and not indeterminate, we retrospectively reviewed the US findings. There were 76 patients who completed the study, and 18 patients (24%) were diagnosed with DVT by duplex US, among whom ED compression US was positive in 14, negative in 2, and indeterminate in 2. Among 58 patients diagnosed without DVT by duplex US, there were 4 false-positive ED compression US examinations and 10 indeterminate examinations. In all, ED compression US was indeterminate in 12 patients (15.8%). Compared to duplex US, ED compression US had a sensitivity of 88.9% (95% C.I. 65.3-98.6%) and specificity of 75.9% (62.8-86.1). Negative predictive value was 95.7% (85.2-99.5). Among ED patients with the clinical diagnosis of possible DVT, negative ED compression US greatly reduces the likelihood of DVT, such that discharge and outpatient follow-up can be considered. Because of limited specificity, positive results require confirmation, but may justify immediate treatment pending follow-up testing. Indeterminate results can be expected in a significant number of patients and mandate further testing prior to disposition.

Utility of lower-extremity duplex sonography in patients with venous thromboembolism

PURPOSE

We evaluated the utility of venous duplex ultrasonography (VDUS) of the lower extremities in patients with pulmonary embolism (PE) and studied the distribution of venous thrombi in deep vein thrombosis (DVT) patients with and without PE.

METHODS

We retrospectively reviewed medical records of all inpatients with a final diagnosis of PE or DVT between 1989 and 2000.

RESULTS

Venous thrombosis was detected by VDUS in 229 patients (191 without PE and 38 with PE). The left leg only was involved in 50% of patients (p < 0.05), the right leg only in 33%, and both legs in 17%. The overall distribution of veins affected by DVT was: popliteal vein, 77%; superficial femoral vein, 76%; common femoral vein, 65%; posterior tibial vein, 23%; external iliac vein, 21%; common iliac vein, 9%; great saphenous vein, 7%; and inferior vena cava, 2%. A single venous site was involved in 22% of patients. External iliac vein thrombosis was more frequent in patients with DVT only (24%) than with PE and DVT (5%) (p < 0.05). The venous obstruction was partial in 14% of patients. VDUS of the asymptomatic leg was positive in 14% of patients with unilateral symptoms of DVT, all of whom also had DVT in the symptomatic leg. VDUS was positive for DVT in 90% of patients with PE and concomitant pain or edema of the leg, compared to only 20% of PE patients with no symptoms of DVT.

CONCLUSIONS

Sonography should be the first diagnostic test for patients suspected of having PE with any sign or symptom related to DVT. VDUS of the asymptomatic leg is unnecessary in the diagnosis and management of DVT. Omitting the superficial femoral vein examination would lead to some decrease in the sensitivity of VDUS.

Do emergency physicians save time when locating a live intrauterine pregnancy with bedside ultrasonography?

OBJECTIVE

To determine whether patients presenting to the emergency department (ED) with first-trimester pregnancy complications have a decreased length of stay (LOS) when a live intrauterine pregnancy (IUP) is diagnosed by emergency physicians (EPs).

METHODS

This study was performed at an urban community ED with a residency program and an annual census of 65,000. A retrospective chart review from October 1995 to August 1998 identified 1,419 patients who received ultrasound examinations confirming live IUP in the first trimester with pain and/or bleeding. Two hundred seventy-seven of these patients received their ultrasound examinations from EPs; 1, 142 patients received a study from radiology and were not scanned by EPs. The LOSs for the two groups were compared and defined as the time from being placed into a room to discharge from the ED. Significance was determined using a two-tailed t-test. Median times with confidence intervals were calculated.

RESULTS

When patients had a live IUP confirmed by an EP, the median LOS was 21% (59 min) less than those who received an ultrasound examination by radiology (p = 0.0001; 95% CI = 49 min to 1 hr 17 min). When evaluated by time of day, patients who presented after hours (6 PM to 6 AM) and were scanned by EPs spent 28% (1 hr 17 min) less time in the ED (p = 0.0001; 95% CI = 55 min to 1 hr 37 min).

CONCLUSIONS

Emergency physicians identifying live IUP with bedside ultrasonography significantly decreased patients' LOSs in the ED. The decrease in LOS was most apparent for patients presenting during evening and nighttime hours.

Lower-extremity Doppler for deep venous thrombosis--can emergency physicians be accurate and fast?

Clinical diagnosis of lower-extremity (LE) deep venous thrombosis (DVT) requires confirmation by an imaging study before committing the patient to anticoagulation therapy. Studies have shown that demonstrating compressibility of leg veins under ultrasound is accurate for ruling out DVTs when performed by vascular specialists. Although LE Doppler has become the preferred test for diagnosing DVTs, it is not always available 24 hours per day.

OBJECTIVES

To evaluate the accuracy and speed with which emergency physicians (EPs) could perform LE color duplex ultrasonography for the detection of DVT.

METHODS

Patients presenting to an urban community emergency department (ED) between August 1, 1998, and March 3, 1999, were enrolled into this prospective study. The EPs, who underwent brief and standardized training, scanned patients at high risk for DVT with leg pain, swelling, or both. Physicians performed color duplex ultrasound examinations with compression at the common femoral and popliteal veins. The time until completion of the ED scan was recorded with a standardized method. The vascular laboratory performed a complete duplex ultrasound examination within eight hours.

RESULTS

One hundred twelve patients were enrolled in the study, with 34 positive for DVT. The median examination time was 3 minutes 28 seconds (95% CI = 2 min 45 sec to 4 min 2 sec; IQR 3 min 9 sec). Times ranged from 1:02 to 18:20 minutes. The ED results had a high correlation with vascular laboratory studies, giving a kappa of 0.9 and a 98% agreement (95% CI = 95.4% to 100%).

CONCLUSION

Emergency physicians can perform LE duplex ultrasound examinations accurately and quickly.

Deep venous thrombosis: recent advances and optimal investigation with US

Compression US is the imaging procedure of choice for patients with clinically suspected DVT of the lower and upper extremities. Clinical trials have validated the safety of the approach of relying on two negative US studies obtained 1 week apart to safely exclude the diagnosis of DVT. In selected low-risk patients, the diagnosis of DVT may be excluded by a single negative US study. US has a role to play in the management of patients with suspected pulmonary embolism who have nondiagnostic pulmonary imaging studies.

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

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

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.

Validation of an inexpensive B-mode ultrasound device for detection of deep vein thrombosis

OBJECTIVE

To validate a portable, inexpensive, real-time, B-mode ultrasound device compared with duplex ultrasound in the detection of proximal lower extremity deep vein thrombosis in hospitalized patients clinically suspected of having deep vein thrombosis.

DESIGN

Prospective cohort study.

SETTING

Tertiary care community teaching hospital.

PATIENTS

Medical-surgical hospitalized patients undergoing duplex ultrasonography for clinically suspected lower extremity deep vein thrombosis.

INTERVENTIONS

Hospitalized patients who underwent duplex ultrasound examinations were enrolled in the study. Blinded from the duplex ultrasound results, the investigators utilized the study ultrasound device to perform compression ultrasonography of the common femoral, superficial femoral, and popliteal veins within 48 h of the duplex examinations. The results of the study ultrasound device were recorded as normal (compressible) or abnormal (noncompressible).

RESULTS

Of the 198 lower limbs evaluated, duplex ultrasonography documented 34 proximal lower extremity deep vein thrombi. The study ultrasound device detected 32 of the 34 proximal thrombi detected by duplex ultrasonography. One false-positive result of an examination occurred with the study ultrasound device. Compared with duplex ultrasonography, the study ultrasound device had a sensitivity of 94%, specificity of 99%, positive predictive value of 97%, and negative predictive value of 98%.

CONCLUSIONS

The results of this investigation document that the study ultrasound device has an acceptable sensitivity, specificity, and diagnostic accuracy for clinical use in detection of proximal lower extremity deep vein thrombosis. Further evaluation and validation of this ultrasound device are warranted.