A detailed analysis of equivocal duplex findings in patients with suspected deep venous thrombosis

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.

Ultrasound for Lower Extremity Deep Venous Thrombosis

Venous ultrasound is the standard imaging test for patients suspected of having acute deep venous thrombosis (DVT). There is variability and disagreement among authoritative groups regarding the necessary components of the test. Some protocols include scanning the entire lower extremity, whereas others recommend scans limited to the thigh and knee supplemented with serial testing. Some protocols use gray-scale ultrasound alone, whereas others include Doppler interrogation. Point-of-care ultrasound is recommended in some settings, and there is heterogeneity of these protocols as well. Heterogeneity of recommendations can lead to errors including incorrect application of guidelines, confusion among requesting physicians, and incorrect follow-up. In October 2016, the Society of Radiologists in Ultrasound convened a multidisciplinary panel of experts to evaluate the current evidence to develop recommendations regarding ultrasound protocols for DVT and the terminology used to communicate results to clinicians. Recommendations were made after open discussion and by unanimous consensus.

The panel recommends a comprehensive duplex ultrasound protocol from thigh to ankle with Doppler at selected sites rather than a limited or complete compression-only examination. This protocol is currently performed in many facilities and is achievable with standard ultrasound equipment and personnel. The use of these recommendations will increase the diagnosis of calf DVT and provide better data to explain the presenting symptoms. The panel recommends a single point-of-care protocol that minimizes underdiagnoses of proximal DVT.

The panel recommends the term chronic postthrombotic change to describe the residual material that persists after the acute presentation of DVT to avoid potential overtreatment of prior thrombus.

Adoption of a single standardized comprehensive duplex ultrasound and a single point-of-care examination will enhance patient safety and clinicians’ confidence.

High sensitivity with color duplex sonography in thrombosis screening after ankle fracture surgery

BACKGROUND

Phlebography is regarded as the reference standard for diagnosing asymptomatic deep vein thrombosis (DVT) in studies of thromboprophylaxis. However, technical advances with noninvasive color duplex sonography (CDS) have made this procedure an interesting alternative.

OBJECTIVES

The objective of the present prospective study was to compare the sensitivity and specificity of CDS with those of phlebography.

PATIENTS

The first 180 consecutive patients included in a larger randomized trial for prolonged thromboprophylaxis were subject to unilateral CDS and to phlebography after ankle fracture surgery. The patients were examined 6 weeks after surgery, all examinations being evaluated blindly. After patient drop outs and exclusions, 144 patients were left for analysis.

RESULTS

Phlebography and CDS examinations were inconclusive or were not completed for 19% of these patients (28/144). DVT was diagnosed by phlebography in 21% (24/116) of the remaining patients. Most of the thrombi were isolated calf DVTs (18/24). In contrast, DVT was diagnosed by CDS in 31% of these patients (36/116): only one case diagnosed by phlebography was missed by CDS. The specificity of CDS is thus 86% and its sensitivity is 96%. The positive predictive value is 64%, and the negative predictive value is 99%.

CONCLUSIONS

CDS is a safe method for detecting asymptomatic distal DVT. It has a high sensitivity and high negative predictive value, which means that the method is highly reliable to rule out DVT. Our results indicate that CDS could be considered as an alternative method for DVT screening.

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.

Complete compression ultrasound for the diagnosis of venous thromboembolism

PURPOSE OF REVIEW

Since its first appearance in the 1980s, venous ultrasound has increasingly gained interest of both clinicians and researchers. However, a majority of authors currently are convinced that venous ultrasound has inherent limitations that preclude it from safely ruling out distal deep vein thrombosis (DVT) in symptomatic patients and from detecting proximal and distal DVT accurately in asymptomatic patients. The aim of this review is to present recent lines of evidence indicating that venous ultrasound has developed beyond these limitations.

RECENT FINDINGS

The major development does not arise from technical progress of imaging but from standardizing the examination procedure. The most efficient protocols now focus on B-mode sonography only but extend the examination to the paired deep calf veins and the calf muscle veins. For such an examination protocol, the term complete compression ultrasound (CCUS) has been coined. Interobserver variability of CCUS resembles that of venography, as do the technical failure rates. By means of a CCUS protocol, the diagnostic work-up of patients with suspected DVT can be simplified significantly. Studies in asymptomatic patients indicate that CCUS has the potential to generate valid data in prevalence and incidence studies and in intervention trials.

SUMMARY

Complete compression ultrasound protocols are ready for implementation into clinical practice for diagnosing patients with symptomatic DVT. Research has already benefited from CCUS and benefits further with an increasing number of CCUS-driven trial designs. However, the value of a CCUS protocol critically depends on sound training and on strict compliance with all its details.