Femoral Vein: The vein accompanying the femoral artery in the same sheath; it is a continuation of the popliteal vein and becomes the external iliac vein.Veins: The vessels carrying blood away from the capillary beds.Saphenous Vein: The vein which drains the foot and leg.Popliteal Vein: The vein formed by the union of the anterior and posterior tibial veins; it courses through the popliteal space and becomes the femoral vein.Iliac Vein: A vein on either side of the body which is formed by the union of the external and internal iliac veins and passes upward to join with its fellow of the opposite side to form the inferior vena cava.Varicose Veins: Enlarged and tortuous VEINS.Portal Vein: A short thick vein formed by union of the superior mesenteric vein and the splenic vein.Venous Insufficiency: Impaired venous blood flow or venous return (venous stasis), usually caused by inadequate venous valves. Venous insufficiency often occurs in the legs, and is associated with EDEMA and sometimes with VENOUS STASIS ULCERS at the ankle.Venous Valves: Flaps within the VEINS that allow the blood to flow only in one direction. They are usually in the medium size veins that carry blood to the heart against gravity.Phlebography: Radiographic visualization or recording of a vein after the injection of contrast medium.Jugular Veins: Veins in the neck which drain the brain, face, and neck into the brachiocephalic or subclavian veins.Venous Thrombosis: The formation or presence of a blood clot (THROMBUS) within a vein.Ultrasonography, Doppler, Duplex: Ultrasonography applying the Doppler effect combined with real-time imaging. The real-time image is created by rapid movement of the ultrasound beam. A powerful advantage of this technique is the ability to estimate the velocity of flow from the Doppler shift frequency.Pulmonary Veins: The veins that return the oxygenated blood from the lungs to the left atrium of the heart.Mesenteric Veins: Veins which return blood from the intestines; the inferior mesenteric vein empties into the splenic vein, the superior mesenteric vein joins the splenic vein to form the portal vein.Thigh: The portion of the leg in humans and other animals found between the HIP and KNEE.Catheterization, Peripheral: Insertion of a catheter into a peripheral artery, vein, or airway for diagnostic or therapeutic purposes.Leg: The inferior part of the lower extremity between the KNEE and the ANKLE.Thrombophlebitis: Inflammation of a vein associated with a blood clot (THROMBUS).Femoral Artery: The main artery of the thigh, a continuation of the external iliac artery.Subclavian Vein: The continuation of the axillary vein which follows the subclavian artery and then joins the internal jugular vein to form the brachiocephalic vein.Hepatic Veins: Veins which drain the liver.Vena Cava, Inferior: The venous trunk which receives blood from the lower extremities and from the pelvic and abdominal organs.Vascular Malformations: A spectrum of congenital, inherited, or acquired abnormalities in BLOOD VESSELS that can adversely affect the normal blood flow in ARTERIES or VEINS. Most are congenital defects such as abnormal communications between blood vessels (fistula), shunting of arterial blood directly into veins bypassing the CAPILLARIES (arteriovenous malformations), formation of large dilated blood blood-filled vessels (cavernous angioma), and swollen capillaries (capillary telangiectases). In rare cases, vascular malformations can result from trauma or diseases.Vascular Patency: The degree to which BLOOD VESSELS are not blocked or obstructed.Catheterization, Central Venous: Placement of an intravenous CATHETER in the subclavian, jugular, or other central vein.Renal Veins: Short thick veins which return blood from the kidneys to the vena cava.Venous Pressure: The blood pressure in the VEINS. It is usually measured to assess the filling PRESSURE to the HEART VENTRICLE.Umbilical Veins: Venous vessels in the umbilical cord. They carry oxygenated, nutrient-rich blood from the mother to the FETUS via the PLACENTA. In humans, there is normally one umbilical vein.Vascular Surgical Procedures: Operative procedures for the treatment of vascular disorders.Arteriovenous Shunt, Surgical: Surgical shunt allowing direct passage of blood from an artery to a vein. (From Dorland, 28th ed)Vascular Grafting: Surgical insertion of BLOOD VESSEL PROSTHESES, or transplanted BLOOD VESSELS, or other biological material to repair injured or diseased blood vessels.Varicose Ulcer: Skin breakdown or ulceration caused by VARICOSE VEINS in which there is too much hydrostatic pressure in the superficial venous system of the leg. Venous hypertension leads to increased pressure in the capillary bed, transudation of fluid and proteins into the interstitial space, altering blood flow and supply of nutrients to the skin and subcutaneous tissues, and eventual ulceration.Vena Cava Filters: Mechanical devices inserted in the inferior vena cava that prevent the migration of blood clots from deep venous thrombosis of the leg.Catheters, Indwelling: Catheters designed to be left within an organ or passage for an extended period of time.Vascular Neoplasms: Neoplasms located in the vasculature system, such as ARTERIES and VEINS. They are differentiated from neoplasms of vascular tissue (NEOPLASMS, VASCULAR TISSUE), such as ANGIOFIBROMA or HEMANGIOMA.Lower Extremity: The region of the lower limb in animals, extending from the gluteal region to the FOOT, and including the BUTTOCKS; HIP; and LEG.Thrombosis: Formation and development of a thrombus or blood clot in the blood vessel.Pulmonary Embolism: Blocking of the PULMONARY ARTERY or one of its branches by an EMBOLUS.Blood Flow Velocity: A value equal to the total volume flow divided by the cross-sectional area of the vascular bed.Dogs: The domestic dog, Canis familiaris, comprising about 400 breeds, of the carnivore family CANIDAE. They are worldwide in distribution and live in association with people. (Walker's Mammals of the World, 5th ed, p1065)Phlebotomy: The techniques used to draw blood from a vein for diagnostic purposes or for treatment of certain blood disorders such as erythrocytosis, hemochromatosis, polycythemia vera, and porphyria cutanea tarda.Splenic Vein: Vein formed by the union (at the hilus of the spleen) of several small veins from the stomach, pancreas, spleen and mesentery.Cardiac Catheterization: Procedures in which placement of CARDIAC CATHETERS is performed for therapeutic or diagnostic procedures.Blood Vessel Prosthesis: Device constructed of either synthetic or biological material that is used for the repair of injured or diseased blood vessels.Cerebral Veins: Veins draining the cerebrum.Regional Blood Flow: The flow of BLOOD through or around an organ or region of the body.Ultrasonography, Doppler, Color: Ultrasonography applying the Doppler effect, with the superposition of flow information as colors on a gray scale in a real-time image. This type of ultrasonography is well-suited to identifying the location of high-velocity flow (such as in a stenosis) or of mapping the extent of flow in a certain region.Catheterization: Use or insertion of a tubular device into a duct, blood vessel, hollow organ, or body cavity for injecting or withdrawing fluids for diagnostic or therapeutic purposes. It differs from INTUBATION in that the tube here is used to restore or maintain patency in obstructions.Dissection: The separation and isolation of tissues for surgical purposes, or for the analysis or study of their structures.Bandages: Material used for wrapping or binding any part of the body.Central Venous Pressure: The blood pressure in the central large VEINS of the body. It is distinguished from peripheral venous pressure which occurs in an extremity.Constriction, Pathologic: The condition of an anatomical structure's being constricted beyond normal dimensions.Time Factors: Elements of limited time intervals, contributing to particular results or situations.Treatment Outcome: Evaluation undertaken to assess the results or consequences of management and procedures used in combating disease in order to determine the efficacy, effectiveness, safety, and practicability of these interventions in individual cases or series.Postthrombotic Syndrome: A condition caused by one or more episodes of DEEP VEIN THROMBOSIS, usually the blood clots are lodged in the legs. Clinical features include EDEMA; PAIN; aching; heaviness; and MUSCLE CRAMP in the leg. When severe leg swelling leads to skin breakdown, it is called venous STASIS ULCER.Retinal Vein: Central retinal vein and its tributaries. It runs a short course within the optic nerve and then leaves and empties into the superior ophthalmic vein or cavernous sinus.Ligation: Application of a ligature to tie a vessel or strangulate a part.Graft Occlusion, Vascular: Obstruction of flow in biological or prosthetic vascular grafts.Azygos Vein: A vein which arises from the right ascending lumbar vein or the vena cava, enters the thorax through the aortic orifice in the diaphragm, and terminates in the superior vena cava.Cadaver: A dead body, usually a human body.Brachiocephalic Veins: Large veins on either side of the root of the neck formed by the junction of the internal jugular and subclavian veins. They drain blood from the head, neck, and upper extremities, and unite to form the superior vena cava.Polytetrafluoroethylene: Homopolymer of tetrafluoroethylene. Nonflammable, tough, inert plastic tubing or sheeting; used to line vessels, insulate, protect or lubricate apparatus; also as filter, coating for surgical implants or as prosthetic material. Synonyms: Fluoroflex; Fluoroplast; Ftoroplast; Halon; Polyfene; PTFE; Tetron.Polyethylene Terephthalates: Polyester polymers formed from terephthalic acid or its esters and ethylene glycol. They can be formed into tapes, films or pulled into fibers that are pressed into meshes or woven into fabrics.Blood Vessel Prosthesis Implantation: Surgical insertion of BLOOD VESSEL PROSTHESES to repair injured or diseased blood vessels.Anastomosis, Surgical: Surgical union or shunt between ducts, tubes or vessels. It may be end-to-end, end-to-side, side-to-end, or side-to-side.Gravity Suits: Double-layered inflatable suits which, when inflated, exert pressure on the lower part of the wearer's body. The suits are used to improve or stabilize the circulatory state, i.e., to prevent hypotension, control hemorrhage, and regulate blood pressure. The suits are also used by pilots under positive acceleration.Saccharum: A plant genus of the family POACEAE widely cultivated in the tropics for the sweet cane that is processed into sugar.Axillary Vein: The venous trunk of the upper limb; a continuation of the basilar and brachial veins running from the lower border of the teres major muscle to the outer border of the first rib where it becomes the subclavian vein.