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What is Chronic venous insufficiency and explain in detail?
Chronic venous insufficiency (CVI) is a medical condition in which blood pools in the veins, straining the walls of the vein. The most common cause of CVI is superficial venous reflux which is a treatable condition. As functional venous valves are required to provide for efficient blood return from the lower extremities, this condition typically affects the legs. If the impaired vein function causes significant symptoms, such as swelling and ulcer formation, it is referred to as chronic venous disease. It is sometimes called chronic peripheral venous insufficiency and should not be confused with post-thrombotic syndrome in which the deep veins have been damaged by previous deep vein thrombosis.
Most cases of CVI can be improved with treatments to the superficial venous system or stenting the deep system. Varicose veins for example can now be treated by local anesthetic endovenous surgery.
Rates of CVI are higher in women than in men. Other risk factors include genetics, smoking, obesity, pregnancy, and prolonged standing.

Signs and symptoms
Signs and symptoms of CVI in the leg include the following:

Varicose veins
Itching (pruritus)
Hyperpigmentation
Phlebetic lymphedema
Chronic swelling of the legs and ankles
Venous ulcerationCVI in the leg may cause the following:

Venous stasis
Ulcers
Stasis dermatitis, also known as varicose eczema
Contact dermatitis, a disrupted epidermal barrier due to venous insufficiency, making patients more susceptible than the general population to contact sensitization and subsequent dermatitis.
Atrophie blanche, an end point of a variety of conditions that appears as atrophic plaques of ivory white skin with telangiectasias. It represents late sequelae of lipodermatosclerosis where the skin has lost its nutrient blood flow.
Lipodermatosclerosis,  an indurated plaque in the medial malleolus.
Malignancy, malignant degeneration being a rare but important complication of venous disease since tumors that develop in the setting of an ulcer tend to be more aggressive.
Pain, a feature of venous disease often overlooked and commonly undertreated.
Anxiety
Depression
Inflammation
Cellulitis

Causes
The most common cause of chronic venous insufficiency is reflux of the venous valves of superficial veins. This may in turn be caused by several conditions:

Deep vein thrombosis (DVT), that is, blood clots in the deep veins. Chronic venous insufficiency caused by DVT may be described as postthrombotic syndrome. DVT triggers an inflammatory response subsequently injuring the vein wall.
Superficial vein thrombosis.
Phlebitis
May–Thurner syndrome. This is a rare condition in which blood clots occur in the iliofemoral vein due to compression of the blood vessels in the leg. The specific problem is compression of the left common iliac vein by the overlying right common iliac artery. Many May-Thurner compressions are overlooked when there is no blood clot. More and more of them get nowadays diagnosed and treated (by stenting) due to advanced imaging techniques.Deep and superficial vein thrombosis may in turn be caused by thrombophilia, which is an increased propensity of forming blood clots.Arteriovenous fistula (an abnormal connection or passageway between an artery and a vein) may cause chronic venous insufficiency even with working vein valves.

Diagnosis
History and examination by a clinician for characteristic signs and symptoms are sufficient in many cases in ruling out systemic causes of venous hypertension such as hypervolemia and heart failure. A duplex ultrasound (doppler ultrasonography and b-mode) can detect venous obstruction or valvular incompetence as the cause, and is used for planning venous ablation procedures, but it is not necessary in suspected venous insufficiency where surgical intervention is not indicated.Insufficiency within a venous segment is defined as reflux of more than 0.5 seconds with distal compression. Invasive venography can be used in patients who may require surgery or have suspicion of venous stenosis. Other modalities that may be employed are: ankle-brachial index to exclude arterial pathology, air or photoplethysmography, intravascular ultrasound, and ambulatory venous pressures, which provides a global assessment of venous competence. Venous plethysmography can assess for reflux and muscle pump dysfunction but the test is laborious and rarely done.The venous filling time after the patient is asked to stand up from a seated position also is used to assess for CVI. Rapid filling of the legs less than 20 seconds is abnormal.

Classification
CEAP classification is based on Clinical, Etiological (causal), Anatomical, and Pathophysiological factors. According to Widmer Classification for assessment of chronic venous insufficiency (CVI), diagnosis of chronic venous insufficiency is clearly differentiated from varicose veins. It has been developed to guide decision-making in chronic venous insufficiency evaluation and treatment.The CEAP classification for CVI is as follows:
Clinical
C0: no obvious feature of venous disease
C1: the presence of reticular or spider veins
C2: Obvious varicose veins
C3: Presence of edema but no skin changes
C4: skin discoloration, pigmentation
C5: Ulcer that has healed
C6: Acute ulcer
Etiology
Primary
Secondary (trauma, birth control pill)
Congenital (Klipper trenaunay)
No cause is known
Anatomic
Superficial
Deep
Perforator
No obvious anatomic location
Pathophysiology
Obstruction, thrombosis
Reflux
Obstruction and reflux
No venous pathology

Management
Conservative
Conservative treatment of CVI in the leg involves symptomatic treatment and efforts to prevent the condition from getting worse instead of effecting a cure. This may include

Manual compression lymphatic massage therapy
Red vine leaf extract may have a therapeutic benefit.
Sequential compression pump
Ankle pump
Compression stockings
Blood pressure medicine
Hydroxyethylrutoside medication
Frequent periods of rest elevating the legs above the heart level
Tilting the bed so that the feet are above the heart. This may be achieved by using a 20 cm (7-inch) bed wedge or sleeping in a 6 degree Trendelenburg position.

Surgical
Surgical treatment of CVI attempts a cure by physically changing the veins with incompetent valves