Duplex ultrasound in upper and lower limb deep venous thrombosis

Duplex ultrasound involves B-mode and Doppler ultrasound. Duplex ultrasonography is a radiological examination requested by clinicians in patients with symptoms of deep venous thrombosis such as upper or lower limb swelling, pain and tenderness. Deep venous thrombosis is a pathology in which clot formation causes obstruction of blood fl ow. The lower limbs are more affected by DVT than upper limbs. Several radiological investigations may be helpful to make the diagnosis. Ultrasound remains a non-ionic, non-invasive, cheaper, available and accurate investigation for prompt diagnosis of DVT however Duplex USG must be done by a radiologist or an experimented sonographer. The sonographic fi ndings may be of acute or chronic DVT. In acute DVT, the intra luminal blood clot is hypoechoic or anechoic whereas in chronic DVT, it is hyperechoic with peripheral revascularization on color Doppler imaging. The results of Doppler ultrasound are sent to clinicians for good treatment plan and follow-up. The treatment is urgent in acute DVT to prevent pulmonary embolism, a life-threatening complication with high mortality rate. Review Article Duplex ultrasound in upper and lower limb deep venous thrombosis Tsongo V Sosthène1*, Kahatwa K Serge2, Kabuyaya K Medard3, Kighoma V Simplice4, Musubao K John4 and Serugendo S Albin5 1MMED RAD, Makerere University Kampala (MUK), HEAL Africa Hospital, Department of Radiology, Lecturer at University of Great Lakes’ Countries (ULPGL), Goma, D.R.Congo 2MMED, MUK, Department of Internal Medicine, HEAL Africa Hospital, D.R Congo, Goma 3Department of Surgery, MMED General Surgery, University of Rwanda, HEAL Africa Hospital, D.R Congo, Goma 4Department of Orthopaedics & Traumatology, MMED in Orthopaedics & Traumatology, MUK, HEAL Africa Hospital, D.R Congo, Goma 5Department of Internal Medicine, MMED, MUK, HEAL Africa Hospital, D.R Congo, Goma Received: 17 December, 2019 Accepted: 10 February, 2020 Published: 12 February, 2020 *Corresponding author: Tsongo Vululi Sosthène, MMED RAD, Makerere University Kampala (MUK), HEAL Africa Hospital, Department of Radiology, Lecturer at University of Great Lakes’ Countries (ULPGL), Goma, D.R.Congo, Phone No: +243994215947, E-mail:


Introduction
Duplex ultrasonography is useful to diagnose DVT and subsequently prevent pulmonary embolism. The awareness of risk factors, clinical and sonographic fi ndings lead to accurate diagnosis of DVT [1,2]. This section is focused on the role of Duplex USG in the diagnosis of upper or lower extremity DVT. The examination requires basic knowledge of upper or lower limb deep venous anatomy and skills in ultrasound scan technique [3]. There is no need of patient's preparation for this examination. The examination may be done in thirty to forty-fi ve minutes. The technique includes B-mode, compression ultrasound and Doppler ultrasound scan [1]. The sonographic patterns of different types of DVT are discussed below. Treatment plan and follow up are mandatory to prevent PE. Several studies have been done on DVT; fi ndings of those oriented in the domain of ultrasonography are discussed below.

Recall of upper and lower limb deep venous anatomy
The upper limb deep venous anatomy: The upper limb is drained by superfi cial and deep veins. The cephalic vein receives blood from the arm through superfi cial cephalic vein and basilica vein. The cephalic vein is located in the subcutaneous fat of the lateral aspect of the arm.

Risk factors for DVT and clinical fi ndings
Deep vein thrombosis is the medical condition in which blood clot is formed in the deep veins [6]. There are numerous risk factors leading to blood clot formation.
Classically, the risk factors are summarized in Virchow triad. Many years ago, Rudolf Virchow described three risk factors associated with venous thrombosis development. The triad of Virchow involves venous blood fl ow stasis, hypercoagulability and endothelial injury. Several studies in the domain of venous thromboembolism revealed so many risk factors according to different categories of patients, their history, health status and treatment received [6,7].
Risk factors include age, bed rest, congestive heart failure, estrogen, family history, hematologic cancers, HIV patients on ART with high viral load, prolonged immobility, indwelling catheters, long-distance travel, major trauma, noninfectious infl ammatory conditions, obesity, pregnancy (and postpartum status), history of Venous Thromboembolism (VTE), recent surgery, smoking, solid cancers, stroke, and thrombophilia. History of DVT increases the risk of recurrence. About 30% of patients who have had DVT will have it again [7].
Symptoms depend on the type of DVT. The ability to characterize DVT as acute or chronic is a diffi cult clinical problem. The signs and symptoms of acute DVT include pain, erythema, and swelling. Tenderness may be present along the course of the involved veins, and a cord may be palpable especially in superfi cial vein thrombosis. There may be increased tissue turgor, distention of superfi cial veins, and the appearance of prominent venous collaterals. In some patients, deoxygenated hemoglobin in stagnant veins imparts a cyanotic hue to the limb, a condition called phlegmasia cerulean dolens. In markedly edematous legs, the interstitial tissue pressure may exceed the capillary perfusion pressure, causing pallor, a condition designated phlegmasia alba dolens. The most common complaint in suspected DVT of the calf is pain. Homans' sign is positive. The knee is in the fl exed position then forcibly dorsifl exion of the ankle cause calf pain. Pain in the calf with this maneuver may be consistent with the diagnosis of deep venous thrombosis [8,9].
The local symptoms are due to obstruction or phlebitis: Doppler. The examination is done by a radiologist or a sonographer with skills in Doppler studies [6,14].
There is no need of patient preparation.
The radiologist or the sonographer will explain to the patient the examination in the purpose to get his consent and cooperation while doing the scan.  The thrombosed vein is usually dilated and fi lled with the thrombus. The thrombus is hypoechoic unfortunately some acute thrombi are anechoic (Figure 2). It is usually diffi cult to visualize anechoic thrombus. Lack of complete venous compressibility is the hallmark sonographic sign of DVT [21,22]. The affected deep vein is initially dilated however as the thrombus ages, it resumes its normal caliber. Changes in vein caliber with respiration and the Valsalva maneuver are not seen in the majority of patients with DVT. This fi nding is present only in the proximal thigh, so it is not usually helpful below the bifurcation of the common femoral vein. The location of thrombus above or below the knee helps to investigate the risk of Pulmonary Embolism (PE) knowing that proximal DVT has a higher risk of PE. In extensive DVT, the thrombus is seen in the external iliac vein or in the great saphenous vein. Thrombus may also be seen in superfi cial veins [23][24][25][26].
On color Doppler sonography, fl ow is usually absent in the area of the thrombus. Peripheral blood fl ow is also outlined by color Doppler imaging. Collaterals are often visualized as prominent venous structures in the soft tissues surrounding the thrombosed main vein. Spectral analysis is useful in the evaluation of central deep venous thrombosis in which the anechoic thrombus may be diffi cult to identify. In some cases, reduction of blood fl ow and lack of venous compressibility are enough to diagnose DVT. Color fl ow Doppler ultrasound in patients with DVT shows either a persistent fi lling defect or thrombus in the color column seen in the lumen or the absence of color fl ow. Color Doppler is most helpful in deep segments of the thigh, pelvic, and calf veins [27,28].
Chronic DVT: It is often clinically diffi cult to differentiate acute from chronic DVT. Initially the thrombus is either anechoic or hypoechoic then it becomes hyperechoic after changes within the lumen of the affected deep vein including clot retraction, chronic occlusion and wall thickening ( Figure 3). Poor visualization of the thrombus and partial compressibility are noted. The thrombus may be adherent to the thickened vessel wall. Diagnosis of chronic DVT does not rely on compression sonography only knowing that it may lead to false positive cases due to thickening of vessel wall following phlebitis. Color fl ow Doppler ultrasound often plays a big role in differentiating acute from chronic DVT. In most of patients, partial compressibility and peri thrombotic blood fl ow are seen in chronic DVT [29,30]. Findings suggestive of chronic DVT with color fl ow Doppler imaging include irregular echogenic vein walls, thickening of the vein walls due to retracted thrombus, calcifi ed retracted thrombus, decreased diameter of the venous lumina, atretic venous segments, well-developed collateral veins, associated deep venous insuffi ciency, and absence of distended veins containing hypoechoic or isoechoic thrombus [31]. Recanalization of the vein after an acute thrombotic event is noted in chronic DVT. Blood fl ow is seen around hyperechoic thrombus.
Discussion of study fi ndings: Diagnosis of DVT of the extremities requires a good clinical examination followed by a radiological examination for confi rmation of the diagnosis. Several radiological studies have been used for the diagnosis of DVT such as duplex ultrasound scan, contrast venography, CT scan venography and MRI venography [32].
Duplex Ultrasound is the initial imaging modality of choice for diagnosing DVT. It is non-invasive, cheaper, available, does not require nephrotoxic contrast agents and reproducible technique with high sensitivity and specifi city. It doesn't use ionizing radiation. Furthermore, duplex ultrasound can be performed at the bed-side and is widely available.
The cephalic, axillary and subclavian veins are well demonstrated on ultrasound scan. The iliac vein, common femoral vein, deep femoral vein, femoral vein, popliteal vein and tributaries are also well seen on ultrasound. Noncompressibility of venous segment, intraluminal thrombus and fl ow abnormality are suffi cient for the diagnosis of DVT of the upper extremities [33]. This modality is not used for suspected thrombus in the brachiocephalic vein and above the external iliac vein visible only on venography and magnetic resonance angiography. Radiologists have approved to consider duplex USG as initial investigation in patients with DVT however this examination shows limitation in upper limb thrombosis. Study fi ndings have shown that sensitivity and specifi city of duplex ultrasonography were 82% (95% CI, 70% to 93%) and 82% (95% CI, 72% to 92%), respectively [34]. Other study showed that duplex USG is a rapid, accurate, and noninvasive technique in the evaluation of venous thrombosis in the upper extremity. It remains the modality of choice in screening for UEDVT [35]. However, MR or contrast venography may be helpful in select cases when sonographic fi ndings are non-diagnostic or equivocal or when clinical suspicion for UEDVT remains high despite normal Doppler fi ndings [36].
Lower Extremity Deep Venous Thrombosis (LEDVT) is well investigated on duplex ultrasound. Several studies have shown that compression ultrasound is accurate in the diagnosis of LEDVT. This method may be used as a screening test in patients with high risk of DVT. Early diagnosis will help to prevent pulmonary embolism (PE), a life-threatening complication which has a high mortality rate [6].
Study fi ndings revealed a prevalence of DVT of 9.1% in HIV positive patients on ART attending an outpatient clinic at Mulago Hospital in Uganda. Majority of patients found with DVT had clinical symptoms of this pathology and only few patients had latent DVT (2.3%). Almost half of HIV patients with DVT (48.6%) had a lower Wells score for DVT therefore this study recommend a screening duplex ultrasound scan in HIV positive patients on ART second line history of prolonged immobility and low CD4 count (<200 cells/μl) [13].
Other studies showed that Well's score remains helpful to clinicians for good selection of patients who may undergo duplex ultrasound however a screening compression ultrasound scan combined with color Doppler is still useful for early diagnosis and prevention of complications [37]. Compression US has been procedure of choice for investigation of suspected upper and lower extremity DVT for decades. Other modifi cation to this technique like two-point compression US, extended compression US (and complete compression US are used in different combinations at different institutions [33]. Compression ultrasonography is highly sensitive and specifi c modality for diagnosing LEDVT [29][30][31][32][33][34][35][36][37][38].
Studies have shown that contrasted venography is standard in the diagnosis of DVT when ultrasound scan is negative in asymptomatic patients for the pathology [39]. Normal fi ndings of lower or upper limb duplex ultrasound do not exclude the possibility of venous thrombosis. Contrast venography is a radiological procedure performed using approximately 20ml iodinated contrast in a concentration of 240-300mg I/ ml. Venography demonstrates the venous anatomy very well therefore a thrombus is well seen as a fi lling defect. It is often diffi cult to insert a cannula in an edematous limb while doing the procedure. Some patients may also present allergic reaction to iodinated contrast agents therefore venography should be done only if suspicion of DVT remains high despite negative USG [33].
Magnetic Resonance Angiography remains an accurate, noninvasive imaging modality for diagnosing DVT in the central thoracic veins such as superior vena cava and brachiocephalic vein. This radiological investigation correlates extremely well with contrast venography. It provides complete assessment of central collaterals and venous blood fl ow [33].
CT scan Venography has the ability to detect central thrombus especially in brachiocephalic vein thrombosis. It is able to demonstrate the extension of proximal lower limb DVT in iliac veins and inferior vena cava. This imaging modality requires injection of contrast media gent. Hence patients with history of allergy to iodine should undergo MRA or USG [33].
Although the accuracy of contrast venography is high than Duplex ultrasound for diagnosing of upper or lower limb DVT, studies have shown that USG remains useful as an initial radiological investigation looking for thrombus in deep veins. Noninvasive duplex USG has replaced contrast venography as the gold standard for screening of LEDVT. The sensitivity for thrombosis detection is about 97%, with a high negative predictive value (98%) when compression ultrasound is complemented by Doppler color fl ow evaluation [40].

Conclusion
Diagnosis of upper or lower deep venous thrombosis is made by clinicians and sonographers after a good clinical examination followed by radiological investigations such as Duplex USG, contrast venography, CT venography or MR venography. Duplex USG is the initial imaging modality of choice in the diagnosis of DVT. It is available, non-invasive and free of radiation however this investigation is operator dependent. Patients may be symptomatic or asymptomatic for DVT. Screening compression ultrasound is useful in patients with high risk for the disease. Sonographic fi ndings of acute DVT include anechoic or hypoechoic thrombus and lack of venous compressibility. Chronic DVT is characterized by the presence of echogenic thrombus within the vessel's lumen with partial compressibility and peripheral revascularization or collaterals seen on duplex USG. Duplex USG shows limitation to diagnose thrombosis in brachiocephalic vein or super vena cava for the upper extremities as well in pelvic deep veins or inferior vena cava for lower extremities therefore other radiological investigations such as contrast venography or Magnetic Resonance Venography are recommended. Studies have shown that Duplex USG remains a rapid, accurate and noninvasive technique in the evaluation of venous thrombosis in both upper and lower limbs.