(Venogram-Renal, Renal Venography, Venogram of the Kidneys)
What is a renal venogram?
A renal venogram is a diagnostic procedure that provides information about the circulatory health of the kidneys. A renal venogram uses X-rays and intravenous (IV) contrast dye to visualize the veins within the kidneys and the veins carrying blood away from the kidneys. Contrast dye causes the blood vessels to appear opaque on the X-ray image, allowing the doctor to visualize the blood vessels being evaluated.
Fluoroscopy is often used during a renal venogram. Fluoroscopy is a study of moving body structures similar to an X-ray movie. A continuous X-ray beam is passed through the body part being examined, and is transmitted to a TV-like monitor so that the body part and its motion can be seen in detail.
In addition to evaluating the renal veins, hypertension (high blood pressure) may be assessed during a renal venogram. A blood sample (renin assay) is obtained from each renal vein. The level of renin in the blood may help the doctor determine the cause of hypertension.
What is an X-ray?
X-rays use invisible electromagnetic energy beams to produce images of internal tissues, bones, and organs on film. X-rays are made by using external radiation to produce images of the body, its organs, and other internal structures for diagnostic purposes. X-rays pass through body structures onto specially-treated plates (similar to camera film) and a "negative" type picture is made (the more solid a structure is, the whiter it appears on the film).
Other related procedures that may be used to diagnose problems of the kidney's blood flow include computed tomography (CT scan) of the kidneys, renal ultrasound, renal angiogram, and pyelogram (intravenous, antegrade, and retrograde). Please see these procedures for additional information.
How do the kidneys work?
The body takes nutrients from food and converts them to energy. After the body has taken the food that it needs, waste products are left behind in the bowel and in the blood.
The kidneys and urinary system keep chemicals, such as potassium and sodium, and water in balance, and remove a type of waste, called urea, from the blood. Urea is produced when foods containing protein, such as meat, poultry, and certain vegetables, are broken down in the body. Urea is carried in the bloodstream to the kidneys.
Two kidneys, a pair of purplish-brown organs, are located below the ribs toward the middle of the back. Their function is to:
Remove liquid waste from the blood in the form of urine
Keep a stable balance of salts and other substances in the blood
Produce erythropoietin, a hormone that aids the formation of red blood cells
Regulate blood pressure
The kidneys remove urea from the blood through tiny filtering units called nephrons. Each nephron consists of a ball formed of small blood capillaries, called a glomerulus, and a small tube called a renal tubule.
Urea, together with water and other waste substances, forms the urine as it passes through the nephrons and down the renal tubules of the kidney.
Reasons for the procedure
The veins in a healthy kidney are free from obstruction, clots, or high blood pressure (hypertension). Some medical conditions may impede blood flow through the kidneys or cause increased blood pressure to the kidneys. If a problem with the veins of the kidney is suspected, your doctor may request a renal venogram to determine the cause of the problem.
A venogram can detect conditions stemming from the renal vein itself, as well as other problems that result from influences on the renal vein from other organs, such as the kidneys. Problems involving renal circulation include structural problems that can lead to a blockage of blood flow to or from the kidneys.
Problems involving the renal circulatory system may include, but are not limited to, the following:
Renal vein thrombosis. An acute or chronic problem in which a blood clot forms in the renal vein. It can occur for various reasons including, but not limited to: postoperative complication after abdominal surgery, dehydration, congestive heart failure, kidney disease, pregnancy, and morbid obesity.
Retroperitoneal fibrosis. A mass of fibrous tissue located towards the back of the abdomen near the kidneys. This mass may cause compression of the renal veins impeding normal blood flow.
Renal tumors. Benign (noncancerous) or malignant (cancerous) tumors on or inside the kidneys
Renal agenesis. Absence of one kidney
Renovascular hypertension. High blood pressure in the kidneys resulting from abnormal hormone levels that are produced or regulated in the kidneys