Free-floating thrombus in the femoral vein - a challenge in phlebologic diagnostics

ARTICLE

Saphenous vein thrombophlebitis (SVT) is generally characterized by lack of significant progression and quick resolution. In most cases it may be treated effectively by means of external graduated compression and non-steroidal anti-inflammatory therapy. If thrombophlebitis affects a larger area and deeper veins show involvement, the guidelines of the German Phlebological Society state that the patient must be treated with heparin and concomitant oral anticoagulants. Conventional or low-weight heparin is to be adminstered immediately in therapeutic doses [1]. The treatment options have still not been compared with each other, and therefore still have to be proven. Deep venous involvement and the risk of pulmonary embolism have been reported much more frequently with SVT than commonly thought [2-6].

Recently there has been an increase in reports of clinically and phlebographically undiagnosed involvement of the saphenofemoral junction and of the deep vein system, as technical improvements in duplex and colour-coded duplex sonography now allow detailed examination of the extent of SVT [7]. There remains controversy [3, 5, 8-10] regarding whether superficial and deep vein thromboses can develop simultaneously at different sites, as well as whether deep vein thromboses lead to involvement of the superficial venous system [11]. In terms of the danger to the patient, the most clinically important consequence of SVT is ascending progression into the deep venous system through the saphenofemoral junction [12]. In 70% of these cases, there is involvement of the femoral vein. When this occurs, free-floating thrombi and the concomitant danger of embolisation into the lung are shown to be common [4, 13-16]. Zollinger et al. reported an incidence of pulmonary embolism in 10.1% of the patients they examined with femoral thrombophlebitis [17]. Pacouret et al., however, did not observe a higher risk for pulmonary embolism in their study of 95 patients [18].

The diagnosis of thrombophlebitis of large veins and the determination of localization and proximal expansion of a thrombus is therefore of particular importance in estimating the risk of embolism and subsequent choice of treatment. Some believe that ascending phlebography is still a gold standard or reference for diagnosing deep venous thromboses in the legs [19, 20]. Yet the proximal great saphenous vein and the saphenofemoral junction are especially difficult to assess with this diagnostic technique with multiple reports of false-negative findings [8, 15, 21-23]. Colour duplex sonography features high levels of sensitivity and specificity, even in depicting floating thrombi in the area of the saphenofemoral junction [8, 24]. In this case report, we discuss a patient with a free-floating thrombus in the left femoral vein to illustrate diagnostic pitfalls and to discuss therapy of extension of thrombus from the great saphenous vein, the so-called "collar button thrombosis".

Case report

History

A 73-year-old male presented with chronic venous insufficiency of the left lower extremity which had been accompanied for one year by an increasing sensation of heaviness and oedema. There was no known previous history of thrombosis or thrombophlebitis. The patient had been wearing a thigh high graduated compression stocking (30-40 mmHg) for three weeks with improvement of symptoms. Just prior to the visit, the patient noted some minor pain in the left chest without shortness of breath or coughing.

Family history was positive for deep venous thrombosis of the lower extremities in the father. The patient did not take any medication on a regular basis.

Physical examination

The patient measured 171 cm and 70 kg and was in a good state of general health. An examination of the lower extremities revealed a dilated, partially distended great saphenous vein on the left side, which was not sensitive to pressure and had varicose lateral tributaries in the dorsal proximal calf in the medial area of the knee. A tender, sinuous vein on the back of the right thigh was visible all the way to the lateral side of the right lower extremity. There was neither unilateral increase in size nor oedema. The posterior and anterior tibial arteries were easily palpable on both ankles. Blood pressure measured 155/90 mmHg on the right and 175/105 on the left; heart rate was 68 bpm.

Laboratory

All parameters were determined before any therapy began. Functional protein S deficiency (35%, normal levels 60-140%) and decreased antithrombin III levels (63.97%, normal levels: 75-125%) were detected. APC sensitivity was low at 1.24 (normal levels: 1.8-2.13). The factor-V analysis showed a heterozygous gene mutation on one allele. ESR measured 2/6. Other laboratory values were in the normal range.

Diagnostic evaluation

Arterial Doppler: there was no evidence of peripheral arterial occlusive disease.

Light reflection rheography: right borderline normal venous backflow (23 s); evidence of abbreviated venous backflow time (T = 14 s) on the left. No normalization could be obtained after administration of an occlusion test (T = 19 s).

Venous occlusion plethysmography: venous capacity after a 3 min interval on both sides was slightly increased at 5.1 ml/100 ml tissue. Venous outflow was in normal ranges on both sides (r. 53 ml and l. 61 ml/100 ml tissue per min).

Colour duplex sonography of the veins of the lower extremities:

The right lower extremity showed a clinically normal superficial and deep venous system.

A wide junctional valve was found on the left and shown to be incompetent upon administration of the Valsalva pressure test. In the saphenofemoral junction area of the great saphenous vein a mobile finger-like and largely sonogenic structure was notable; it extended into the lumen of the femoral vein and floated upon breathing (Figs. 1 and 2). The diameter of the femoral vein at rest was 1.22 cm. The lumen was almost completely displaced due to the structure (diameter 1.00 cm). In the deep femoral and tibial veins distal compression yielded a good flow. A Valsalva test showed no evidence of retrograde blood flow. The entire great saphenous vein was non-compressible. The final interpretation was floating thrombus into the left femoral vein with concomitant pre-existing ascending thrombophlebitis of the great saphenous vein.

Electrocardiography: sinus rhythm at a rate of 68/min; indeterminate axis. No cardiac conduction disorders or repolarisation disorders. No evidence of dilation of right ventricle.

Treatment and course

Immediately after diagnosis, subcutaneous low-molecular-weight heparin in therapeutic dosage (0.6 ml Nadroparin-Fraxiparin^® s.c. at 70 kg BW) was administered. The patient was transferred to hospital on the same day to determine the further course of treatment (thrombectomy, thrombolysis, anticoagulation). Once admitted, additional phlebography and duplex sonography of the left lower extremity were performed. Ascending phlebography revealed no obstruction in the entire deep venous system (crural veins, popliteal vein, superficial femoral vein, deep femoral vein, common femoral vein, external femoral vein, lower inferior vena cava). However there was no evidence seen of newly developed or older thrombotic material (Fig. 3A and B). The conclusion was that the apparent filling defect in the saphenofemoral junction area could be explained by an influx phenomenon and did not correspond to a thrombus or to a floating thrombus. Duplex sonography revealed a thickened vein wall with an older adherent thrombus near the femoral vein with no evidence of floating thrombus.

Based on these findings, the patient was released without additional therapy. A colour duplex sonographic follow-up exam was performed on the next day in our surgery. This showed that the thrombus was unchanged in its size and shape. The patient was re-admitted to hospital, where a thrombectomy was indicated and then promptly performed. The intraoperative diagnosis was a large floating and adherent, older thrombus extending from the great saphenous vein into the femoral vein. Histology showed small passages of a wall of a vein with foci of fibroses and macrophages (apparently a developing thrombus) and segments of an older coagulation thrombus with signs of organization. There was no evidence of malignancy. Post-operative heparinisation with Fraxiparin (2 x 0.6 ml s.c. per day) occurred for a three-month period as the patient rejected oral anticoagulant therapy. Compression therapy was continued. A long-term anticoagulant therapy was rejected by the patient in spite of extensive discussion of consent.

Discussion

Ascending thrombophlebitis of the great saphenous vein with extension into the femoral vein greatly increases the risk of pulmonary embolism [4, 5, 12-17, 25, 26]. Ascending contrast phlebography was introduced by Bauer in 1940 to diagnose deep venous thromboses [27] and is still considered by some as the reference standard for verifying or ruling out the presence of thromboses [18, 19, 28, 29]. Limitations of phlebography include failure to adequately visualize the deep femoral vein [30], verification of thrombosis of the gastrocnemius and soleus veins [20, 23] and the need for an experienced eye to distinguish between old and new thrombus [23]. Other drawbacks include risks of allergy to contrast medium, renal complications [31], and puncture of the dorsal venous arch [28, 31].

Colour-coded high-resolution duplex sonography has numerous advantages as a non-invasive procedure which allows simultaneous morphologic and haemodynamic depictions of the superficial and deep vein system [8, 12, 14-16, 22, 24, 28, 31-34]. Compression sonography (B-mode compression sonography) without colour-coded flow imaging and pulsed Doppler technique makes it possible to differentiate between open and thrombotic vascular lumen. Saphenofemoral junction areas, deep femoral veins and muscular veins can be clearly shown with free-floating thrombus clearly distinguished from adherent material. The newly developed power Doppler mode allows visualization of very slow marginal or residual flow in thrombotic veins with a mild compression manoeuvre [35]. The lowest detectable flow with the power doppler technique is 0.5 mm/s (in vitro measurements) [36]. Duplex allows non-invasive monitoring of clot progression and therapy which can be repeated frequently if necessary.

The ability to diagnose by duplex ultrasound, however, is dependent upon use of modern, high-resolution ultrasound equipment which makes exact, clear images possible for optimal diagnosis. Examination results also depend on the individual training and experience of the operator. A pulse repetition frequency in the colour depiction that is too high brings about an aliasing effect, or it images colours poorly or not at all in cases of slow rates of blood flow [35]. Often it is difficult to show the course of the tibial veins, especially in the case of overweight or oedematous extremities.

In our case report, a floating thrombus in the region of the saphenofemoral junction could not be confirmed in the hospital either by phlebography or by duplex sonography. It is known that thromboses at the junction of the great and small saphenous veins can not always be detected using phlebolography [8, 15, 21-23, 32]. An inconsistent filling defect near the saphenofemoral junction on the venogram was mistakenly interpreted as an influx phenomenon of blood without contrast medium [23]. The colour duplex false-negative findings were probably due to the fact that the non-occlusive thrombus or floating thrombus appeared unchanged during the colour duplex exam by breathing and modulation compression tests [35].

False-positive results are also possible when duplex sonography is used. In a study by Kock et al., for example, even experienced angiologic examiners with high-quality equipment could not intraoperatively confirm 11% of the cases of preoperatively diagnosed thrombi around the saphenofemoral junctions [26]. Another study also found no intraoperative correlation in 11% of the cases in which duplex sonography had previously "confirmed" thromboses near the saphenofemoral junction (floating thrombus in the femoral vein; up to the proximal saphenofemoral valve; or within the saphenofemoral junction area). In six out of seven cases, however, free-floating thrombi were correctly identified using colour duplex sonography [6], a fact which reflects the high sensitivity and specificity of this method.

Verrel et al. suggested a four-stage classification of ascending varicophlebitis so that therapeutic recommendations could be standardized and categorized; its localization and extent would determine whether treatment is to be performed with maintenance therapy or operation [37]. These statements, however, are given as recommendations which still have to be proven.

A case of isolated thrombophlebitis in which the proximal end of the thrombus is at a safe distance from the saphenofemoral junction is thus to be treated with non-steroidal, anti-inflammatory therapy, subcutaneous administration of heparin and compression therapy (type I). The therapy of thrombophlebitis near the saphenofemoral junction includes the out-patient subcutaneous administration of therapeutic dosages of low-molecular heparins with concomitant high-resolution colour duplex sonographic monitoring. If the proximal end of the thrombus reaches the beginning of the saphenofemoral area, the therapy of choice is a saphenofemoral junction ligation and saphenectomy (type II) [9, 37]. In the case of extension of the thrombus into the deep venous system (type III) or the presence of floating thrombi, a thrombectomy is also to be recommended [37] and/or oral anticoagulant therapy for 2-6 months [9, 18, 37, 38]. Type IV according to Verrel et al. describes the exceptional situation of a thrombus extended via insufficient perforator veins and is predominantly treated with maintenance therapy. Treatment is thus guided by the extent and location of thrombophlebitis. This is best revealed by colour duplex sonography by trained operators.

CONCLUSION

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