Renal Veins: Short thick veins which return blood from the kidneys to the vena cava.Veins: The vessels carrying blood away from the capillary beds.Vena Cava, Inferior: The venous trunk which receives blood from the lower extremities and from the pelvic and abdominal organs.Renal Nutcracker Syndrome: Left RENAL VEIN compression between the AORTA, ABDOMINAL and the SUPERIOR MESENTERIC ARTERY. Variable symptoms include HYPERTENSION, RENOVASCULAR; HEMATURIA; and VARICOSE VEINS.Portal Vein: A short thick vein formed by union of the superior mesenteric vein and the splenic vein.Saphenous Vein: The vein which drains the foot and leg.Flank Pain: Pain emanating from below the RIBS and above the ILIUM.Varicocele: A condition characterized by the dilated tortuous veins of the SPERMATIC CORD with a marked left-sided predominance. Adverse effect on male fertility occurs when varicocele leads to an increased scrotal (and testicular) temperature and reduced testicular volume.Renal Artery: A branch of the abdominal aorta which supplies the kidneys, adrenal glands and ureters.Varicose Veins: Enlarged and tortuous VEINS.Phlebography: Radiographic visualization or recording of a vein after the injection of contrast medium.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.Hematuria: Presence of blood in the urine.Splenic Vein: Vein formed by the union (at the hilus of the spleen) of several small veins from the stomach, pancreas, spleen and mesentery.Anatomy, Regional: The anatomical study of specific regions or parts of organisms, emphasizing the relationship between the various structures (e.g. muscles, nerves, skeletal, cardiovascular, etc.).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.Pulmonary Veins: The veins that return the oxygenated blood from the lungs to the left atrium of the heart.Constriction, Pathologic: The condition of an anatomical structure's being constricted beyond normal dimensions.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.Venous Thrombosis: The formation or presence of a blood clot (THROMBUS) within a 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.Jugular Veins: Veins in the neck which drain the brain, face, and neck into the brachiocephalic or subclavian veins.Neoplasms, Vascular Tissue: Neoplasms composed of vascular tissue. This concept does not refer to neoplasms located in blood vessels.Kidney: Body organ that filters blood for the secretion of URINE and that regulates ion concentrations.Nephrectomy: Excision of kidney.Renal Artery Obstruction: Narrowing or occlusion of the RENAL ARTERY or arteries. It is due usually to ATHEROSCLEROSIS; FIBROMUSCULAR DYSPLASIA; THROMBOSIS; EMBOLISM, or external pressure. The reduced renal perfusion can lead to renovascular hypertension (HYPERTENSION, RENOVASCULAR).Hypertension, Renovascular: Hypertension due to RENAL ARTERY OBSTRUCTION or compression.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.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.Hypertension, Renal: Persistent high BLOOD PRESSURE due to KIDNEY DISEASES, such as those involving the renal parenchyma, the renal vasculature, or tumors that secrete RENIN.Replantation: Restoration of an organ or other structure to its original site.Hepatic Veins: Veins which drain the liver.Vascular Surgical Procedures: Operative procedures for the treatment of vascular disorders.Arteriovenous Fistula: An abnormal direct communication between an artery and a vein without passing through the CAPILLARIES. An A-V fistula usually leads to the formation of a dilated sac-like connection, arteriovenous aneurysm. The locations and size of the shunts determine the degree of effects on the cardiovascular functions such as BLOOD PRESSURE and HEART RATE.Leiomyosarcoma: A sarcoma containing large spindle cells of smooth muscle. Although it rarely occurs in soft tissue, it is common in the viscera. It is the most common soft tissue sarcoma of the gastrointestinal tract and uterus. The median age of patients is 60 years. (From Dorland, 27th ed; Holland et al., Cancer Medicine, 3d ed, p1865)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.Tomography, X-Ray Computed: Tomography using x-ray transmission and a computer algorithm to reconstruct the image.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.Resins, Plant: Flammable, amorphous, vegetable products of secretion or disintegration, usually formed in special cavities of plants. They are generally insoluble in water and soluble in alcohol, carbon tetrachloride, ether, or volatile oils. They are fusible and have a conchoidal fracture. They are the oxidation or polymerization products of the terpenes, and are mixtures of aromatic acids and esters. Most are soft and sticky, but harden after exposure to cold. (From Grant & Hackh's Chemical Dictionary, 5th ed & Dorland, 28th ed)Aorta, Abdominal: The aorta from the DIAPHRAGM to the bifurcation into the right and left common iliac arteries.Nephrotic Syndrome: A condition characterized by severe PROTEINURIA, greater than 3.5 g/day in an average adult. The substantial loss of protein in the urine results in complications such as HYPOPROTEINEMIA; generalized EDEMA; HYPERTENSION; and HYPERLIPIDEMIAS. Diseases associated with nephrotic syndrome generally cause chronic kidney dysfunction.