Superficial venous thrombosis comes in two forms—those close to the treated vein, whether it is a thermal or nonthermal ablation procedure , a ligation, or an excision of a superficial vein, and those unrelated to an interventional or surgical procedure. The most common is related to the procedure and occurs when there is both stagnant flow in a treated vein, due to proximal or distal ligation and injury, or when there is trapped blood within a treated vein, where the proximal and/or distal vein is ligated or thrombosed, so that the blood in between becomes stagnant and eventually thromboses.

SVT may be either asymptomatic or symptomatic, depending on the vein involved, the extent of inflammation within the vein, and the tissue surrounding the vein. SVT in veins that become dilated and inflamed may cause significant discomfort, and those adjacent to sensory nerves may have significant burning as well as pain, while those with minimal inflammation and swelling may be asymptomatic.

There is little data or information on the prevention of SVT in patients undergoing venous procedures, probably because the consequences of SVT are usually not life threatening; they are usually self-limited and of little clinical consequence. The one technical principle to prevent SVT is to remove as much superficial vein as possible when performing excision and not leave large amounts of entrapped blood when performing ablation or sclerotherapy. When SVT occurs after sclerotherapy , where no vein is excised, placement of the solution in the vein is associated with spasm and inflammation of the vein being treated. Consequently, sclerotherapy of larger veins is performed with the leg elevated to collapse the vein, and after injection of the sclerosant, the leg should be compressed until the inflammatory reaction in the vein has become self-limited and the diameter of the thrombus in the vein is the smallest possible. Reducing the volume of blood in a vein with SVT reduces discomfort and later hemosiderin pigmentation related to the vein that is sclerosed [2].

Clinical exam is the primary method of diagnosing SVT. Areas of SVT have localized tenderness, erythema along the vein, and firmness due to the thrombus within the vein. Localized SVT is often confused with infection . Duplex ultrasound is the primary technique to diagnose SVT and is used in cases where the cause of pain is not obvious. When there is concern about the extent of the SVT, duplex ultrasound can also easily identify the proximal and distal extent of the thrombus, determine the size of the thrombosed vein, and determine if it may be amenable to aspiration to release trapped blood.

Treatment is dependent on the degree of patient discomfort and the anticipated cosmetic consequences of untreated SVT. When a large superficial vein is thrombosed, there is considerable likelihood of long-term pigmentation, and therefore treatment may be indicated for cosmetic purposes. In addition, the degree of inflammation and pain will influence treatment. The options for treatment include symptomatic relief with anti-inflammatory medications and topical moist heat compression. When symptoms are severe or the risk of pigmentation is high, the release of entrapped blood with needle or micro-incision, followed by aspiration, usually results in rapid relief of pain and a lower likelihood of long-term pigmentation.

Endothermal heat-induced thrombosis (EHIT) is defined as thrombus extension from a thermally treated superficial truncal vein into the deep system (Fig. 16.2). It may also occur with nonthermal techniques such as mechanochemical ablation (MOCA) , foam, or glue ablation [3]. EHIT occurs at the junction between superficial and deep veins. Since the thrombus originates in the superficial vein and the thrombus extends into the deep vein without deep vein wall attachment, it is not a true DVT and it has a different natural history, unless it remains in the deep vein for a prolonged period and eventually attaches to the wall of the deep vein. In most circumstances, it is self-limited, with retraction of the thrombus back into the superficial vein within days to weeks and with no long-term consequences to the deep venous system. Consequently, the major risk of EHIT is that thrombus will break off during the time when it is unattached and/or floating in the deep venous system.

The location of the tip of a thermal catheter, when the vein is ablated, is critical in determining the likelihood of EHIT (Fig. 16.3). At least 2–3 cm from the junction is the recommended distance to prevent EHIT—the closer to the deep vein, the higher the likelihood that the thrombus will extend into the deep vein. It can occur with any thermal or nonthermal procedure that closes a large superficial axial vein at its junction with the deep venous system. The identification of the extension into the deep system is dependent on the timing of imaging to identify EHIT.

Even though the risk of EHIT is low (<5%), it is the most common concern of the treating physician in patients who have a complication after a superficial endovenous procedure. EHIT is more common in patients with a very large truncal vein, in hypercoagulable patients, and in those patients with a prior history of DVT.

There has been no standardized and validated system of classification of EHIT, but there have been several classification systems proposed, which, although they have some differences, are similar in most ways [4–6].

Differentiating the causes of post-procedure pain and swelling is difficult, and differentiating EHIT from DVT clinically is difficult, unless duplex ultrasound is used to image the site of concern. Because there are significant differences in the natural history and treatment of EHIT and DVT, it is important to determine the etiology of postoperative complications in all patients with pain and swelling.

Not all patients require a DU post-procedure to evaluate them for EHIT or DVT, but patients with significant post-op pain or swelling and those who have high risk factors for DVT and EHIT should undergo DU to assess the site of ablation, for hematoma or superficial branch or truncal vein thrombus. Both B mode and color flow, using transducers in the 2–10 MHz range, should be used for each study (Fig. 16.4). The transducer wavelength used will depend on the patient’s body habitus and the depth of the superficial and deep venous system at the site of the diagnostic study. The diagnostic ultrasound should be performed in both the supine or standing position. Measurements should be taken using an electronic cursor in transverse, axial, and orthogonal positions to determine the distance and relationship between any thrombus identified and the vein wall, as well as the presence, absence, and extent of protrusion into the deep system.