Renal (kidney) and mesenteric (intestinal) artery disease are conditions that develop when the arteries in the abdomen that supply either the kidneys or the intestines become narrowed, or blocked, by an accumulation of a fatty substance called plaque. As plaque builds up inside the artery walls, the arteries can become hardened and narrowed (a process called atherosclerosis). Atherosclerosis affects up to 35 percent of Americans, and can cause narrowing (also called stenosis) of any of the arteries throughout the body. As atherosclerosis affects the whole body, people with renal or mesenteric artery narrowing often have other cardiovascular conditions such as carotid artery disease and heart disease.
In renal artery disease, the narrowed arteries reduce blood flow to the kidneys, causing progressive kidney failure or difficult-to-control high blood pressure in a significant number of patients. In mesenteric artery disease, the arteries supplying blood to the intestines are narrowed; people with this condition lose weight and experience severe pain when they eat.
Risk Factors and Symptoms
Risk factors for renal and mesenteric artery disease include smoking – the number one risk factor for all cardiovascular diseases – a family history of atherosclerosis, high blood pressure, diabetes, high cholesterol, advanced age, obesity, and a sedentary lifestyle. Renal artery disease can also develop as a result of fibromuscular dysplasia (FMD). FMD is a condition in which abnormal cells cause narrowing throughout certain arteries, particularly those that supply the kidneys with blood. FMD can also affect the carotid arteries and arteries in the pelvis. This condition can affect anyone but is often seen in women between the ages of 20 and 40. Less commonly, injuries to the kidney can result in scarring, which can block the arteries to the kidney.
With renal artery disease, patients can develop high blood pressure that is very difficult to control, and in extreme cases kidney failure. With mesenteric artery disease, patients can experience weight loss and severe abdominal pain when they eat.
Doctors use one or more of the following imaging tests to determine the location and the extent of the arterial stenosis:
- Duplex Ultrasound
- Magnetic Resonance Angiography (MRA)
- CT Scan
Minimally Invasive Procedures
Patients whose symptoms are mild to moderate can often manage their disease by making lifestyle changes such as quitting smoking, getting regular exercise, and working with their doctors to take care of related conditions such as diabetes, high blood pressure, and high cholesterol. Doctors often use minimally invasive procedures such as balloon angioplasty and stenting to relieve the narrowing and improve blood supply to the kidney and intestines.
Angiogram: An angiogram is a diagnostic imaging test that allows doctors to view blood vessels throughout the body and diagnose blockages, enlargements, clots, and malformations. An angiogram to study the arteries is called an arteriogram; one to study the veins is called a venogram. To perform these tests, doctors place a tiny, soft plastic tube called a catheter into the artery or vein, usually in the groin, and inject a dye that makes the blood vessels clearly visible on an x-ray image. Vascular specialists at New York-Presbyterian Hospital are often able to both diagnose and treat vascular problems during the same procedure, combining an angiogram with one of the minimally invasive procedures outlined below – balloon angioplasty or stenting.
Balloon angioplasty: During angioplasty, vascular specialists use a special catheter that has a small balloon at the end, which can be inflated and deflated. The deflated balloon catheter is inserted through an artery in the groin and guided to the narrowed segment of the artery. When the catheter reaches the blockage, the balloon is inflated to widen the narrowed artery.
Stenting: In some cases, it may be necessary to place a stent. A stent is a small tube that holds open the artery at the site of the blockage. The stent is collapsed around a balloon when it is placed on the tip of the catheter and inserted into the body. Once the catheter reaches the blockage, the doctor expands the stent by inflating the balloon. The stent is left permanently in the artery to provide a reinforced channel through which blood can flow. Some stents (drug-eluting stents) are coated with medication that helps prevent the formation of scar tissue.
If renal or mesenteric artery disease is very advanced, or if blockages develop in an artery that is difficult to reach with a catheter, arterial bypass surgery may be necessary to restore blood flow.
Arterial Bypass Surgery: To surgically correct the decreased blood flow through the artery, doctors place a bypass graft made of synthetic material or a natural vein taken from another part of the body. During the procedure, the surgeon will make an incision to expose the diseased segment of the artery, and then attach one end of a bypass graft to a point above the blockage and the other end to a point below it. The blood supply is then diverted through the graft, around the blockage, to bypass the diseased section of the artery. The diseased artery is left in place.
Dialysis Access: During dialysis, a patient's blood is passed through an external filter (a hemodialyzer) that performs some of the functions of the kidney: removing wastes, excess fluids, and salts from the blood and correcting levels of specific chemicals. Patients on dialysis have their blood filtered several times a week; to make this process easier, doctors create a window to the bloodstream that allows blood to be removed and returned quickly, efficiently, and safely. The window is usually in the arm and completely beneath the skin.
Doctors use one of two procedures to create a dialysis access, a fistula or a graft. In both cases, an artery is connected to a vein to increase the blood flow through the vein. Over time the vein enlarges, carrying more blood and making it easier for dialysis technicians and nurses to gain access to the bloodstream.
To create a fistula, the surgeon joins an artery to a large, nearby vein. Over the following weeks and months, the vein increases in size. If the vein is blocked or too small to use, doctors will create a graft, an artery-to-vein connection using a synthetic tube instead of the patient's own blood vessels. Because fistulas are constructed using the patient's own blood vessels, they are generally more durable and resistant to infection than grafts.