Superficial varicosities are the result of high-pressure flow into a normally low-pressure system. Varicosities carrying retrograde flow are hemodynamically harmful because they cause recirculation of oxygen-poor, lactate-laden venous blood back into an already congested extremity. The primary goal of treatment is the ablation of these reflux pathways with resulting improvement of venous circulation.
In the rare setting of deep system obstruction, varicosities are hemodynamically helpful because they provide a bypass pathway for venous return. Hemodynamically helpful varices must not be removed or sclerosed. This condition is encountered rarely, but when it is, ablation of these varicosities causes rapid onset of pain and swelling of the extremity, eventually followed by the development of new varicose bypass pathways.
Sclerotherapy, laser and intense-pulsed-light therapy, radiofrequency (RF) or laser ablation,  and ambulatory phlebectomy are the modern techniques used to ablate varicosities. Numerous reports describe success rates of greater than 90% for less invasive techniques, which are associated with fewer complications, with comparable efficacy. [7, 8]
Chemical sclerosis or endovenous chemoablation
Chemical sclerosis or endovenous chemoablation (sclerotherapy) is the most widely used medical procedure for ablation of varicose veins and spider veins.  In this procedure, a sclerosing substance is injected into the abnormal vessels to produce endothelial destruction that is followed by formation of a fibrotic cord and eventually by reabsorption of all vascular tissue layers. For most veins, a detergent sclerosing agent is agitated with air to create a foam similar to shaving foam. A thorough diagnostic evaluation is essential prior to treatment. A high degree of technical skill is necessary for effective sclerotherapy many reasons.
Local treatment of the superficial manifestations of venous insufficiency is unsuccessful if the underlying high points of reflux have not been found and treated. Even when the patient appears to have only primary telangiectasias and the initial treatment seems to be successful, recurrences are observed very quickly if unrecognized reflux exists in larger subsurface vessels.
Missing the diagnosis of superficial truncal incompetence can cause significant complications (especially skin staining and telangiectatic matting) if spider veins and superficial tributaries are treated while high-pressure feeders remain open.
Delivery of sclerosant to subsurface feeding vessels that are not visible is usually performed under ultrasonographic guidance.
Missing the diagnosis of deep system disease can lead to bad outcomes in several ways. Symptoms become immediately worse if an unrecognized bypass pathway is ablated. Missing the diagnosis of underlying venous thrombosis can lead to fatal embolism.  Unrecognized deep venous insufficiency can lead to early or immediate recurrence of treated superficial disease. 
Selection of the correct sclerosant and the correct volume and concentration of sclerosant depends on the type and location of disease, internal volume of the vessel to be treated, positioning of the patient, and many other factors. The minimum effective concentration and volume should always be used because sclerosant inevitably passes into the deep venous system, where endothelial injury can lead to disastrous consequences.
Some sclerosants (eg, hypertonic sodium chloride solution) are highly caustic. Extravasation of even a single drop of these agents can lead to skin sloughing and a very poor cosmetic result.
Inadvertent injection into an arteriovenous malformation (or directly into an unrecognized underlying artery) can cause extensive tissue loss or loss of the entire limb.
Inadvertent injection of concentrated sclerosants into the deep system can cause deep vein thrombosis, pulmonary embolism, and death.
The proper use of sclerosing agents requires special training and extended study. Specific dosing and technique recommendations for the administration of sclerosants are beyond the scope of this article.
The most commonly used sclerosants today are polidocanol and sodium tetradecyl sulfate, both known as detergent sclerosants because they are amphiphilic substances that are inactive in dilute solution but are biologically active when they form micelles. These agents are preferred because they have a low incidence of allergic reactions, produce a low incidence of staining and other cutaneous adverse effects, and are relatively forgiving if extravasated. 
These are best delivered as a foam, which is made by agitating the solutions with air to create a frothy substance.
Sodium morrhuate is an older detergent sclerosant that is made up of a mixture of saturated and unsaturated fatty acids extracted from cod liver oil. The agent is of variable composition and has been associated with a relatively high incidence of anaphylaxis. The incidence of extravasation necrosis is high with this drug.
Ethanolamine oleate, a synthetic preparation of oleic acid and ethanolamine, has weak detergent properties because its attenuated hydrophobic chain lengths make it excessively soluble and decrease its ability to denature cell surface proteins. High concentrations of the drug are necessary for effective sclerosis. Allergic reactions are uncommon, but reports exist of pneumonitis, pleural effusions, and other pulmonary symptoms following the injection of ethanolamine oleate into esophageal varices. The principal disadvantages of the drug are a high viscosity that makes injection difficult, a tendency to cause red cell hemolysis and hemoglobinuria, the occasional production of renal failure at high doses, the possibility of pulmonary complications, and a relative lack of strength compared with other available sclerosants.
Hypertonic sodium chloride solution in a 20% or 23.4% solution can be used as a sclerosing agent. The principal advantage of the agent is the fact that it is a naturally occurring bodily substance with no molecular toxicity, but the disadvantages of the agent make it unsuitable except in the hands of highly skilled practitioners. Because of dilutional effects, achieving adequate sclerosis of large vessels without exceeding a tolerable salt load is difficult. It can cause significant pain on injection and significant cramping after a treatment session. If extravasated, it almost invariably causes significant necrosis. Seeing patients with dozens of disfiguring scars at the sites of extravasation of hypertonic sodium chloride solution is not uncommon. Because it causes immediate red blood cell hemolysis and rapidly disrupts vascular endothelial continuity, it may cause marked hemosiderin staining that is not cosmetically acceptable.
Food and Drug Administration (FDA) approval of drug labeling is an important concern for physicians and patients in the United States. Polidocanol is approved by the FDA. Sotradecol, sodium morrhuate, and ethanolamine oleate all were developed prior to the establishment of the FDA. These agents are available in the United States as grandfathered agents. The newest form of Sotradecol was cleared by the FDA in 2006. It is highly purified with no contaminants.
In November 2013, the FDA approved polidocanol injectable foam (Varithena), a pharmaceutical-grade, low-nitrogen polidocanol foam dispensed from a proprietary canister device, for the treatment of incompetent veins and visible varicosities of the great saphenous vein system. Approval was based on 2 placebo-controlled studies, in which most of the treated patients experienced clinically meaningful improvement of the symptoms of superficial venous incompetence and the appearance of visible varicosities. 
According the National Institute for Health and Care Excellence (NICE) guidelines, foam sclerotherapy is considered second-therapy after endovenous ablation. 
The safety of sclerosing agents in pregnancy has not been established.
Transcutaneous pulsed dye laser and intense-pulsed-light (IPL) therapy has proven effective for the tiniest surface vessels (eg, those found on the face), but this modality is not generally useful as primary therapy for treatment of spider veins of the lower extremity. This is true for several reasons.
Because of the physics of light absorption, delivering an ablative dose of thermal energy to the vessel without damaging the overlying skin is difficult. The degree of patient-to-patient variability of light absorption in the skin is high. Even an experienced practitioner may inadvertently cause painful skin burns that can lead to permanent hyperpigmentation or hypopigmentation.
For most patients, the laser pulses are significantly more painful than the 30-gauge needles used for microsclerotherapy.
Most spider veins have associated feeding vessels that must be treated by some other means before the tiny surface vessels are amenable to laser or IPL treatment.
Dudelzak et al report successful treatment of facial spider veins (telangiectasias) with a 980-nm diode laser. No complications were reported