Ultrasound diagnostics of acute venous thrombosis
Acute venous thrombosis of the inferior vena cava system is divided into embologenous (floating or non-occlusive) and occlusive. Non-occlusive thrombosis is a source of pulmonary embolism. The superior vena cava system gives only 0.4% of pulmonary embolism, the right heart - 10.4%, while the inferior vena cava is the main source of this formidable complication (84.5%).
A lifetime diagnosis of acute venous thrombosis can be established only in 19.2% of patients who died from pulmonary embolism. The data of other authors indicate that the frequency of correct diagnosis of venous thrombosis before the development of fatal pulmonary embolism is low and ranges from 12.2 to 25%.
Postoperative venous thrombosis is a very serious problem. According to B.C. Saveliev, postoperative venous thrombosis develops after general surgical interventions in an average of 29% of patients, in 19% of cases after gynecological interventions and in 38% of cases of transvesical adenomectomy. In traumatology and orthopedics, this percentage is even higher and reaches 53-59%. A special role is given to the early postoperative diagnosis of acute venous thrombosis. Therefore, all patients who pose a certain risk in terms of postoperative venous thrombosis should undergo a complete examination of the inferior vena cava system at least twice: before and after surgery.
It is considered of fundamental importance to identify violations of the patency of the great veins in patients with arterial insufficiency of the lower extremities. This is especially necessary for a patient in whom surgery is expected to restore arterial circulation in the limb, the effectiveness of such a surgical intervention decreases in the presence of various forms of obstruction of the great veins. Therefore, all patients with limb ischemia should be examined for both arterial and venous vessels.
Despite the significant advances achieved in recent years in the diagnosis and treatment of acute venous thrombosis of the inferior vena cava and peripheral veins of the lower extremities, interest in this problem has not only not diminished in recent years, but is constantly growing. A special role is still assigned to the issues of early diagnosis of acute venous thrombosis.
According to their localization, acute venous thrombosis is subdivided into thrombosis of the ilicaval segment, femoral-popliteal segment and thrombosis of the leg veins. In addition, the large and small saphenous veins can be affected by thrombotic lesions.
The proximal border of acute venous thrombosis can be located in the infrarenal part of the inferior vena cava, suprarenal, reach the right atrium and be in its cavity (echocardiography is shown). Therefore, it is recommended to start the examination of the inferior vena cava from the area of the right atrium and then gradually go down to its infrarenal section and the place where it flows into the inferior vena cava of the iliac veins. It should be noted that the closest attention must be paid not only to the examination of the trunk of the inferior vena cava, but also to the veins flowing into it. First of all, they include the renal veins. Usually, thrombotic lesion of the renal veins is due to the volumetric formation of the kidney. It should not be forgotten that the cause of thrombosis of the inferior vena cava can be the ovarian veins or testicular veins. Theoretically, it is believed that these veins, due to their small diameter, cannot lead to pulmonary thromboembolism, especially since the prevalence of a thrombus to the left renal vein and the inferior vena cava along the left ovarian or testicular vein, due to the tortuosity of the latter, looks casuistic. However, you should always strive to inspect these veins, at least their mouths. In the presence of thrombotic occlusion, these veins slightly increase in size, the lumen becomes heterogeneous and they are well located in their anatomical areas.
In ultrasound triplex scanning, venous thrombosis is subdivided in relation to the lumen of the vessel into parietal, occlusive and floating thrombi.
Ultrasonic signs of parietal thrombosis are considered to be visualization of a thrombus with the presence of free blood flow in this area of the changed lumen of the vein, the absence of complete collapse of the walls during compression of the vein by the sensor, the presence of a filling defect in the CDC, the presence of spontaneous blood flow in spectral Doppler ultrasonography.
Thrombosis is considered occlusive, the signs of which are the absence of wall collapse during compression of the vein with a sensor, as well as visualization of inclusions of various echogenicity in the lumen of the vein, the absence of blood flow and vein staining in spectral Doppler and CDC modes. Ultrasonic criteria for floating thrombi are: visualization of a thrombus as an echogenic structure located in the lumen of a vein with the presence of free space, oscillatory movements of the apex of a thrombus, no contact of the vein walls during compression with a sensor, the presence of free space when performing respiratory tests, bending around the type of blood flow when color coding the flow , the presence of spontaneous blood flow in spectral Doppler ultrasonography.
The possibilities of ultrasound technologies in the diagnosis of the age of thrombotic masses are of constant interest. Identification of signs of floating thrombi at all stages of thrombosis organization can improve the efficiency of diagnostics. Particularly valuable is the earliest diagnosis of fresh thrombosis, which makes it possible to take measures for early prevention of pulmonary embolism.
After comparing the ultrasound data of floating thrombi with the results of morphological studies, we came to the following conclusions.
Ultrasound signs of a red thrombus are hypoechoic fuzzy contour, anechoic thrombus in the apex and hypoechoic distal part with separate echogenic inclusions. Signs of a mixed thrombus are a heterogeneous structure of a thrombus with a hyperechoic clear outline. In the structure of the thrombus in the distal parts, heteroechoic inclusions predominate, in the proximal parts, predominantly hypoechoic inclusions. Signs of a white thrombus are a floating thrombus with clear contours, a mixed structure with a predominance of hyperechoic inclusions, and with CDC, fragmented flows through thrombotic masses are recorded.
Acute venous thrombosis is a common and dangerous disease. According to statistics, its frequency in the general population is about 160 per 100,000 population. Thrombosis in the inferior vena cava (IVC) system is the most frequent and dangerous type of this pathological process and is the main source of pulmonary embolism (84.5%). The superior vena cava system gives 0.4-0.7% pulmonary embolism (PE), the right heart - 10.4%. The share of venous thrombosis of the lower extremities accounts for up to 95% of all thrombosis cases in the IVC system. The diagnosis of acute venous thrombosis is diagnosed in vivo in 19.2% of patients. In the long term, deep vein thrombosis (DVT) leads to the formation of post-thrombophlebitic disease, manifested by chronic venous insufficiency up to the development of trophic ulcers, which significantly reduces the ability to work and the quality of life of patients.
The main mechanisms of intravascular thrombus formation, known since the time of R. Virchow, are a slowdown in blood flow (stasis), hypercoagulation, trauma to the vessel wall (damage to the endothelium). Acute venous thrombosis often develops against the background of various oncological diseases (malignant tumors of the gastrointestinal tract, female genital area, etc.) due to the fact that cancer intoxication causes the development of hypercoagulable changes and suppression of fibrinolysis, as well as due to mechanical compression of the veins by the tumor and germination her into the vascular wall. Obesity, pregnancy, oral hormonal contraceptives, hereditary thrombophilia (deficiency of antithrombin III, protein C and S, Leiden mutation, etc.), systemic connective tissue diseases, chronic purulent infections, allergic reactions are also considered predisposing factors for DVT. Patients of the elderly and senile age and persons suffering from chronic venous insufficiency of the lower extremities, as well as patients with myocardial infarction, decompensated heart failure, stroke, bedsores, gangrene of the lower extremities, are at the highest risk of developing DVT. Traumatological patients are of particular concern, since fractures of the femur are mainly found in elderly and senile people who are most burdened with somatic diseases. Thrombosis in trauma patients can occur with any injury of the lower extremities, since all etiological factors of thrombosis (vascular damage, venous congestion and changes in the blood coagulation properties) take place.
Reliable diagnosis of phlebothrombosis is one of the urgent clinical tasks. Physical examination methods make it possible to make a correct diagnosis only in typical cases of the disease, while the frequency of diagnostic errors reaches 50%. For example, thrombosis of the veins of the gastrocnemius muscles with preserved patency of the remaining veins is often asymptomatic. Because of the danger of missing an acute DVT in the legs, clinicians often make this diagnosis for every pain in the calf muscles. Particular attention should be paid to "trauma" patients in whom the presence of pain, edema and discoloration of the limb may be the result of the trauma itself, and not DVT. Sometimes the first and only manifestation of such a thrombosis is massive PE.
The tasks of instrumental examination include not only confirmation or refutation of the presence of a thrombus, but also determination of its length and degree of embolism. Isolation of embolism-prone thrombi into a separate group and the study of their morphological structure are of great practical importance, since without this it is impossible to develop effective prevention of pulmonary embolism and the choice of optimal treatment tactics. Thromboembolic complications are more often observed in the presence of a floating thrombus with a heterogeneous structure, an uneven hypo- or isoechoic contour, in contrast to thrombi with a hyperechoic contour and a homogeneous structure. An important criterion for the embolism of a thrombus is the degree of its mobility in the lumen of the vessel. Embolic complications are more often observed with pronounced and moderate mobility of thrombosis.
Venous thrombosis is a rather dynamic process. Over time, the processes of retraction, humoral and cell lysis contribute to a decrease in the size of the thrombus. At the same time, the processes of its organization and recanalization are going on. In most cases, the patency of the vessels is gradually restored, the valve apparatus of the veins is destroyed, and the remnants of blood clots in the form of parietal overlays deform the vascular wall. Difficulties in diagnosis can be in case of recurrent acute thrombosis against the background of partially recanalized veins in patients with post-thrombophlebitic disease. In this case, a rather reliable criterion is the difference in veins in diameter: in patients with signs of recanalization of thrombosis, the vein in diameter decreases due to the subsidence of the acute process; with the development of retrombosis, a significant increase in the diameter of the vein again occurs with indistinct ("blurred") contours of the walls and surrounding tissues. The same criteria are used in the differential diagnosis of acute parietal thrombosis with post-thrombotic changes in the veins.
Of all the non-invasive methods used to diagnose thrombosis, ultrasound scanning of the venous system has recently been increasingly used. The method of triplex angioscanning, proposed by Barber in 1974, includes the study of blood vessels in the B-mode, the analysis of the Doppler frequency shift in the form of classical spectral analysis and flux (in velocity and energy modes). The use of spectral has made it possible to accurately measure the blood flow inside the lumen of the veins. The use of the method () made it possible to quickly distinguish occlusive thrombosis from non-occlusive thrombosis, to identify the initial stages of thrombus recanalization, and also to determine the location and size of venous collaterals. In dynamic studies, the ultrasound method provides a fairly accurate control over the effectiveness of thrombolytic therapy. In addition, with the help of ultrasound, it is possible to establish the causes of the appearance of clinical symptoms similar to those in vein pathology, for example, to identify a Baker's cyst, intermuscular hematoma or a tumor. The introduction of expert class ultrasonic devices with transducers with a frequency of 2.5 to 14 MHz made it possible to achieve almost 99% diagnostic accuracy.
Material and methods
The examination included examination of patients with clinical signs of venous thrombosis and PE. Patients complained of edema and pain in the lower (upper) limb, pain in the gastrocnemius muscle (more often of a bursting character), "pulling" pain in the popliteal region, pain and induration along the saphenous veins. Examination revealed moderate cyanosis of the lower leg and foot, dense edema, pain on palpation of the lower leg muscles, in most patients positive symptoms of Homans and Moses.
All subjects underwent triplex scanning of the venous system using modern ultrasound devices with a linear transducer with a frequency of 7 MHz. At the same time, the condition of the thigh veins, popliteal vein, leg veins, as well as the great and small saphenous veins was assessed. A convex probe with a frequency of 3.5 MHz was used to visualize the iliac veins and IVC. When scanning the IVC, iliac veins, great saphenous vein, femoral veins and veins of the lower leg in the distal part of the lower extremities, the patient was in the supine position. The study of the popliteal veins, veins of the upper third of the leg and the lesser saphenous vein was carried out in the patient's prone position with a roller placed under the ankle joint area. Difficulties in diagnostics arose during visualization of the distal part of the superficial femoral vein in obese patients, visualization of leg veins with pronounced trophic and indural tissue changes. In these cases, a convex probe was also used. The scanning depth, echo amplification and other parameters of the study were selected individually for each patient and kept unchanged during the entire examination, including observations in dynamics.
Scanning was started in cross-section to exclude the presence of a floating apex of the thrombus, as evidenced by full contact of the venous walls during light compression with the transducer. After making sure that there was no free floating apex of the thrombus, the compression test with the sensor was performed from segment to segment, from proximal to distal. The proposed technique is the most accurate not only for detecting thrombosis, but also for determining its extent (excluding the iliac veins and IVC, where the patency of the veins was determined in the CDC mode). veins confirmed the presence and characteristics of venous thrombosis. In addition, a longitudinal section was used to locate the anatomical fusion of the veins. During the examination, the condition of the walls, the lumen of the veins, the localization of the thrombus, its length, and the degree of fixation to the vascular wall were assessed.
Ultrasound characterization of venous thrombi was carried out in relation to the lumen of the vessel: they were distinguished as parietal, occluding and floating thrombi. Signs of parietal thrombosis were visualization of a thrombus with the presence of free blood flow in the lumen of the vein, the absence of complete collapse of the walls during compression of the vein with a sensor, the presence of a filling defect in CDC, and the presence of spontaneous blood flow in spectral Doppler (Fig. 1).
Rice. 1. Non-occlusive popliteal vein thrombosis. Longitudinal vein scan. The envelope blood flow in the energy flow coding mode.
The ultrasound criteria for floating thrombi were: visualization of a thrombus as an echogenic structure located in the lumen of a vein with the presence of free space, oscillatory movements of the apex of a thrombus, no contact of the vein walls during compression with a sensor, the presence of free space when performing respiratory tests, bending type of blood flow in CPC, the presence of spontaneous blood flow with spectral Doppler. When a floating thrombus was detected, the degree of its mobility was assessed: pronounced - in the presence of spontaneous thrombus movements with calm breathing and / or holding the breath; moderate - when oscillatory movements of a thrombus are detected during functional tests (cough test); insignificant - with minimal mobility of a thrombus in response to functional tests.
Research results
From 2003 to 2006, 236 patients aged 20 to 78 years were examined, of which 214 with acute thrombosis clinic and 22 with pulmonary embolism clinic.
In the first group, in 82 (38.3%) cases, the patency of deep and superficial veins was not disturbed and the clinical symptoms were due to other reasons (Table 1).
Table 1... Conditions with symptoms similar to DVT.
The diagnosis of thrombosis was confirmed in 132 (61.7%) patients, while in most cases (94%) thrombosis was detected in the IVC system. DVT was detected in 47% of cases, superficial veins - in 39%, damage to both the deep and superficial venous systems was observed in 14%, including 5 patients with the involvement of perforating veins.
Probable causes (risk factors) for the development of venous thrombosis are presented in Table. 2.
table 2... Thrombosis risk factors.
| Risk factor | Number of patients | |
|---|---|---|
| abs. | % | |
| Trauma (including prolonged plaster immobilization) | 41 | 31,0 |
| Varicose veins | 26 | 19,7 |
| Malignant neoplasms | 23 | 17,4 |
| Operations | 16 | 12,1 |
| Taking hormonal drugs | 9 | 6,8 |
| Thrombophilia | 6 | 4,5 |
| Chronic limb ischemia | 6 | 4,5 |
| Iatrogenic causes | 5 | 4,0 |
In our observations, the most common form of thrombosis, as well as lesions of the veins at the level of the popliteal-tibial and femoral-popliteal segments, were most often detected (Table 3).
Table 3... Localization of DVT.
More often (63%) there were thrombosis, completely occluding the lumen of the vessel, in second place in frequency (30.2%) were parietal thrombi. Floating thrombi were diagnosed in 6.8% of cases: in 1 patient - in the saphenofemoral anastomosis with ascending thrombosis of the trunk of the great saphenous vein, in 1 - ileofemoral thrombosis with a floating apex in the common iliac vein, in 5 - in the common femoral vein with thrombosis of the femoropopliteal segment and in 2 - in the popliteal vein with DVT of the lower leg.
The length of the non-fixed (floating) part of the thrombus, according to ultrasound data, varied from 2 to 8 cm. Moderate mobility of thrombotic masses was more often detected (5 patients), in 3 cases the mobility of the thrombus was minimal. In 1 patient, with calm breathing, spontaneous movements of the thrombus in the lumen of the vessel were visualized (high degree of mobility). In our observations, floating thrombi with a heterogeneous echo structure (7 people) were more often detected, while the hyperechoic component prevailed in the distal section, and the hypoechoic component in the area of the thrombus head (Fig. 2).
Rice. 2. Floating thrombus in the common femoral vein. B-mode, longitudinal vein scan. Thrombus of a heteroechoic structure with a clear hyperechoic contour.
In dynamics, to assess the course of the thrombotic process, 82 patients were examined, of which 63 (76.8%) had partial recanalization of thrombotic masses. In this group, 28 (44.4%) patients had a central type of recanalization (with longitudinal and transverse scanning in the CDC mode, the recanalization canal was visualized in the center of the vessel); in 23 (35%) patients, parietal recanalization of thrombotic masses was diagnosed (more often blood flow was determined along the vein wall, immediately adjacent to the artery of the same name); In 13 (20.6%) patients, incomplete recanalization with fragmentary asymmetric staining in the CDC mode was detected. Thrombotic occlusion of the vein lumen was observed in 5 (6.1%) patients, in 6 (7.3%) cases, the vein lumen was restored. Signs of retrombosis persisted in 8 (9.8%) patients.
conclusions
Comprehensive ultrasound examination, including angioscanning using spectral, color and power Doppler modes and soft tissue echography, is a highly informative and safe method that allows the most reliable and quick solution to the issues of differential diagnosis and treatment tactics in outpatient phlebological practice. It is advisable to conduct this study at the outpatient stage for the earlier identification of patients who are not indicated (and sometimes contraindicated) thrombolytic therapy, and their referral to specialized departments; when confirming the presence of venous thrombosis, it is necessary to identify persons with a high risk of thromboembolic complications; observe the dynamics of the course of the thrombotic process and thereby adjust the treatment tactics.
Literature
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Thrombotic lesion of the venous bed of the lower extremities, especially deep veins, is an acute condition that develops as a result of the complex action of a number of factors. According to the statistical reports of the Ministry of Health of the Russian Federation, 80,000 new cases of this disease are registered in our country every year. In old and senile age, the frequency of deep vein thrombosis increases several times. In Western Europe, this pathology occurs in 3.13% of the population. Venous thrombosis is the main cause of pulmonary thromboembolism. Massive thromboembolism of the pulmonary arteries develops in 32-45% of patients with acute deep vein thrombosis of the lower extremities and ranks third in the overall structure of sudden mortality.
Deep vein thrombosis - This is the formation of a blood clot inside the vessel. When blood clots form, there is an obstacle to the outflow of blood. Venous thrombosis can occur when blood circulation is impaired (blood stagnation), damage to the inner wall of the vessel, increased ability of blood to form a thrombus, or a combination of these reasons. Thrombus formation can begin anywhere in the venous system, but most often in the deep veins of the leg.
Ultrasonic compression duplex angioscanning is the main examination method for suspected venous thrombosis. The main tasks are the identification of a thrombus, a description of its density (this sign is important for diagnosing the timing of thrombosis), fixation to the walls of the vein, length, the presence of floating areas (capable of detachment from the vascular wall and moving with the blood flow), the degree of obstruction.
Also, ultrasound examination allows for dynamic monitoring of the state of the thrombus in the course of the treatment. An active search for deep vein thrombosis using duplex scanning seems appropriate in the preoperative period, as well as in cancer patients. The significance of ultrasound methods in the diagnosis of thrombosis is considered to be quite high: the sensitivity ranges from 64-93%, and the specificity - 83-95%.
Ultrasound examination of the veins of the lower extremities is performed using linear transducers 7 and 3.5 MHz. The study begins with the groin in the transverse and longitudinal sections in relation to the vascular bundle. The mandatory scope of the study includes examination of the saphenous and deep veins of both lower extremities. When obtaining an image of the veins, the following parameters are assessed: diameter, compressibility (compression by the sensor until the blood flow in the vein stops while maintaining blood flow in the artery), features of the course of the vessel, the state of the internal lumen, the safety of the valve apparatus, changes in the walls, the state of the surrounding tissues. The blood flow in the adjacent artery is necessarily assessed. The state of venous hemodynamics is also assessed using special functional tests: respiratory and cough test or straining test (Valsalva test). They are used primarily to assess the condition of the valves of the deep and saphenous veins. In addition, the use of functional tests facilitates visualization and assessment of venous patency in areas with low blood flow velocity. Some of the functional tests may be useful to clarify the proximal border of venous thrombosis. The main signs of thrombosis include the presence of echo-positive thrombotic masses in the lumen of the vessel, the echo density of which increases with the age of the thrombus. At the same time, the valves of the valves cease to differentiate, the transmitting arterial pulsation disappears, the diameter of the thrombosed vein increases by 2-2.5 times in comparison with the contralateral vessel, when it is compressed by the sensor, it is not compressed.
There are 3 types of venous thrombosis: floating thrombosis, occlusive thrombosis, parietal (non-occlusive) thrombosis.
Occlusive thrombosis is characterized by complete fixation of thrombus masses to the venous stack, which prevents the thrombus from turning into an embolus. Signs of parietal thrombosis include the presence of a blood clot with free blood flow in the absence of complete collapse of the venous walls during a compression test. Criteria for a floating thrombus are visualization of a thrombus in the lumen of a vein with the presence of free space, oscillatory movements of the thrombus head, no contact of the vein walls during compression with a sensor, and the presence of free space when performing breathing tests. For the final clarification of the nature of the thrombus, a special Valsalva test is used, which should be carried out with caution in view of the additional flotation of the thrombus.
Ultrasound is a first-line diagnostic method for suspected deep vein thrombosis of the lower extremities. This is facilitated by the relatively low cost, availability and safety of the technique. In GBUZ "Tambov Regional Clinical Hospital named after V.D. Babenko "ultrasound duplex angioscanning of peripheral veins has been performed since 2010. About 2000 studies are carried out annually. High quality diagnostics can save the lives of a large number of people. Our institution is the only one in the region that has a vascular surgery department, which allows determining treatment tactics immediately after a diagnosis is made. Highly qualified doctors successfully use modern methods of treating venous thrombosis.
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