Renal Vascular Disease
Renal Vascular Disease - Description, Causes, and Risk Factors:
Renal vascular disease is the name given to a variety of complications that affect the arteries and veins of the kidneys. These complications affect the blood circulation of the kidneys, and may cause damage to the tissues of the kidneys, kidney failure, and/or high blood pressure.
The cause of renal vascular disease will depend on the specific condition involved:
Renal Artery Stenosis: Stenosis (blockage) of a renal artery may be caused by atherosclerosis (a build-up of plaque, which is a deposit of fatty substances, cholesterol, cellular waste products, calcium, and fibrin in the inner lining of an artery) or other conditions, such as fibromuscular dysplasia (a condition that weakens the walls of medium-sized arteries and occurs predominantly in young women of childbearing age), and Takayasu's arteritis (a rare inflammatory disease affecting the aorta and its branches, including the renal arteries). Atherosclerosis is the cause of about 80 percent to 90 percent of renal artery stenosis.
Renal artery thrombosis: Formation of a thrombosis (clot) inside one of the renal arteries may occur as a result of trauma, infection, inflammatory disease, renal artery aneurysm, or fibromuscular dysplasia.
Renal Artery Aneurysm: There are four types of renal artery aneurysms:
Saccular - bulges or balloons out only on one side of the artery.
- Fusiform - bulges or balloons out on all sides of the artery.
- Dissecting - weakened artery wall due to a tear in the inner layer of the artery wall.
- Intrarenal - occurs on an artery inside the kidney.
- Saccular aneurysms may occur as a result of a congenital (present at birth) weakness of an artery wall or trauma. Atherosclerosis may also be a factor. Fusiform aneurysms most often occur with fibromuscular dysplasia. Intrarenal aneurysms may be congenital, or may result from trauma.
Atheroembolic renal disease: Small pieces of plaque (emboli) from atherosclerosis formation in other arteries of the body may break off and travel to the renal arteries, blocking blood flow to the kidney. Emboli may occur because of surgery, insertion of a catheter, or the use of blood-thinning medications. The disease most commonly affects older persons.
Renal vein thrombosis: Conditions associated with the presence of renal vein thrombosis include trauma, compression of a renal vein by an adjacent structure such as a tumor or aneurysm, nephrotic syndrome (results from damage to the kidneys' glomeruli, the tiny blood vessels that filter waste and excess water from the blood and send them to the bladder as urine), pregnancy, administration of steroid medications, and use of oral contraceptives (birth control pills).
The exact prevalence is difficult to estimate, as the condition may easily go undiagnosed among hypertensive patients, and there is an appreciable prevalence of undiagnosed hypertension in the population at large.
In the USA it is estimated to account for 1-5% of cases of secondary hypertension in the general population, but as much as 30% in vascular high-risk groups, or up to 60% in those aged >70 years.
In a study of UK type 2 diabetics with hypertension (a high-risk group for renovascular disease) and normal serum creatinine levels, using magnetic resonance angiography to detect the disease, a prevalence of 17% was found. 95% of these patients had unilateral disease.
The prevalence of angiographic renal artery stenosis in a group of UK patients undergoing angiography for suspected peripheral vascular disease was 36%.
The condition may present in a variety of ways and is usually asymptomatic. The following clinical scenarios are relatively common modes of presentation:
Abrupt onset of hypertension in middle-aged or older patients.
- Severe hypertension.
- Hypertension resistant to standard medical therapy.
- Hypertension developing in a patient with known peripheral vascular/cerebrovascular/cardiovascular disease.
- Hypertension developing in a patient with no family history of hypertension.
- Biochemical or clinical evidence of renal impairment occurring during treatment with angiotensin-converting enzyme (ACE) inhibitors or angiotensin-II receptor antagonists.
- De novo renal impairment developing in a hypertensive or normotensive patient with vascular disease/risk factors.
- De novo hypertension or renal impairment developing in an older patient who has been previously normotensive.
- Hypertension with hypokalemia (due to hyperaldosteronism) with no provoking medications or other identifiable cause (may be associated with metabolic acidosis).
- Decompensation of congestive cardiac failure in a hypertensive patient (may present with recurrent episodes of acute pulmonary edema with no obvious precipitant - so-called 'flash pulmonary edema').
In addition to a complete medical history and physical examination, diagnostic procedures for renal vascular disease may include any, or a combination, of the following:
Arteriogram (also called an angiogram) - an x-ray image of the blood vessels used to evaluate various conditions, such as aneurysm, stenosis (narrowing of the blood vessel), or blockages. A dye (contrast) will be injected through a thin flexible tube placed in an artery. This dye makes the blood vessels visible on x-ray.
- Duplex ultrasound - a type of vascular ultrasound procedure done to assess blood flow and the structure of the leg veins. The term "duplex" refers to the fact that two modes of ultrasound are used - Doppler and B-mode. The B-mode transducer (like a microphone) obtains an image of the vessel being studied. The Doppler probe within the transducer evaluates the velocity and direction of blood flow in the vessel.
- Renography - a specialized radiology procedure used to assess the function and structure of the kidneys. Renography is a type of nuclear radiology procedure. This means that a tiny amount of a radioactive substance is used during the procedure to assist in the examination of the kidneys.
- Magnetic resonance angiography (MRA) - a noninvasive diagnostic procedure that uses a combination of magnetic resonance technology (MRI) and intravenous (IV) contrast dye to visualize blood vessels. Contrast dye causes blood vessels to appear opaque on the MRI image, allowing the physician to visualize the blood vessels being evaluated.
Renal artery occlusion: If the blockage is found early enough and if there's only one functioning kidney, doctors usually start aggressive treatment. They may use medications called thrombolytics to dissolve blood clots. This treatment can only be done if the blockage isn't complete and if it's done immediately. Immediate treatment is essential since blood flow to the kidneys is essential. They may also try to prevent more clots by using anticoagulants, such as warfarin or heparin.
In severe cases, surgery might be used to try to clean out the artery. Again, surgery must be done shortly after the blockage occurs. It's generally done if the problem has been caused by trauma rather than by a disease.
If the blockage is only partial, balloon angioplasty or renal artery bypass surgery may be considered to improve kidney function or blood pressure control. Occasionally, high blood pressure can be cured following this procedure.
Renal vein thrombosis: The main treatment is to dissolve or prevent further blood clots. Surgery may also be used. In cases of dehydration, liquids are given to restore the body's fluid balance.
Unfortunately, there's no specific treatment for renal atheroembolism. The goal is to prevent it from getting worse.
Renovascular disease can't always be prevented, although its development can be slowed down by controlling conditions that can cause it, such as high blood pressure and diabetes. Eating a healthy diet is always recommended.
In the case of renal vein thrombosis, some embolisms can be prevented by making sure people don't get dehydrated when they're sick. This means drinking enough fluids, especially when ill, for example, with severe gastroenteritis or the flu. This is particularly important for young children.
The chances of developing renal atheroembolism are less if some of the risk factors, such as smoking and overweight, are eliminated. For people with diabetes, controlling blood sugar is very beneficial to reducing the risk of this condition.
NOTE: The above information is for processing purpose. The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition.
DISCLAIMER: This information should not substitute for seeking responsible, professional medical care.
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