Renal artery stenosis
Encyclopedia
Renal artery stenosis is the narrowing of the renal artery
, most often caused by atherosclerosis
or fibromuscular dysplasia
. This narrowing of the renal artery can impede blood flow to the target kidney. Hypertension and atrophy of the affected kidney
may result from renal artery stenosis, ultimately leading to renal failure
if not treated.
may develop if both kidneys are poorly supplied, or when treatment with an ACE inhibitor
is initiated. Some patients present with episodes of flash pulmonary edema
(sudden left ventricular heart failure).
A clinical prediction rule
is available to guide diagnosis.
is the predominant cause in young patients, usually females under 40 years of age. A variety of other causes exist. These include arteritis
, renal artery aneurysm
, extrinsic compression (e.g., neoplasms), neurofibromatosis, and fibrous bands.
of the kidney senses a decreased systemic blood pressure owing to the reduced blood flow through the narrowed artery. The response of the kidney to this perceived decreased blood pressure is activation of the renin-angiotensin aldosterone system
, which normally counteracts low blood pressure but in this case leads to hypertension (high arterial blood pressure). The decreased perfusion pressure (caused by the stenosis) leads to decreased blood flow (hypoperfusion) to the kidney and a decrease in the GFR. If the stenosis is longstanding and severe the GFR in the affected kidneys never increases again and (prerenal) renal failure
is the result.
with or without stent
ing. A 2003 meta-analysis
found that angioplasty was safe and effective in this context, however 7 randomized, controlled trials have not shown any clinical benefit to improve blood pressure or renal function. This includes the ASTRAL trial of 2010, although it was known to have only enrolled patients who would not "clearly" benefit from renal revascularization. There are three other ongoing clinical trials comparing medical management and angioplasty with stenting which include the CORAL trial which is scheduled to report results in early 2011. In addition to angioplasty, surgical revascularization of the renal artery is the "gold standard" and when compared to angioplasty and stenting (RAOOD trial) was found to be equivalent in morbidity and mortality. If all else fails and the kidney is thought to be worsening hypertension and revascularization with angioplasty or surgery doesn't work, then removing the "bad" kidney (nephrectomy) may improve high blood pressure dramatically.
.
Renal artery
The renal arteries normally arise off the side of the abdominal aorta, immediately below the superior mesenteric artery, and supply the kidneys with blood. Each is directed across the crus of the diaphragm, so as to form nearly a right angle with the aorta....
, most often caused by atherosclerosis
Atherosclerosis
Atherosclerosis is a condition in which an artery wall thickens as a result of the accumulation of fatty materials such as cholesterol...
or fibromuscular dysplasia
Fibromuscular dysplasia
Fibromuscular dysplasia, or fibromuscular dysplasia of arteries, often abbreviated as FMD, is a disease that can cause narrowing of arteries in the kidneys, the carotid arteries supplying the brain, and, less commonly, the arteries of the abdomen...
. This narrowing of the renal artery can impede blood flow to the target kidney. Hypertension and atrophy of the affected kidney
Kidney
The kidneys, organs with several functions, serve essential regulatory roles in most animals, including vertebrates and some invertebrates. They are essential in the urinary system and also serve homeostatic functions such as the regulation of electrolytes, maintenance of acid–base balance, and...
may result from renal artery stenosis, ultimately leading to renal failure
Renal failure
Renal failure or kidney failure describes a medical condition in which the kidneys fail to adequately filter toxins and waste products from the blood...
if not treated.
Signs and symptoms
Most cases of renal artery stenosis are asymptomatic, and the main problem is high blood pressure that cannot be controlled with medication. Deterioration in renal functionRenal function
Renal function, in nephrology, is an indication of the state of the kidney and its role in renal physiology. Glomerular filtration rate describes the flow rate of filtered fluid through the kidney...
may develop if both kidneys are poorly supplied, or when treatment with an ACE inhibitor
ACE inhibitor
ACE inhibitors or angiotensin-converting enzyme inhibitors are a group of drugs used primarily for the treatment of hypertension and congestive heart failure...
is initiated. Some patients present with episodes of flash pulmonary edema
Flash pulmonary edema
In medicine, flash pulmonary edema , is rapid onset pulmonary edema. It is most often precipitated by acute myocardial infarction or mitral regurgitation, but can be caused by aortic regurgitation, heart failure, or almost any cause of elevated left ventricular filling pressures...
(sudden left ventricular heart failure).
Diagnosis
- refractory hypertensionHypertensionHypertension or high blood pressure is a cardiac chronic medical condition in which the systemic arterial blood pressure is elevated. What that means is that the heart is having to work harder than it should to pump the blood around the body. Blood pressure involves two measurements, systolic and...
- high blood pressure that cannot be controlled adequately with antihypertensives - auscultationAuscultationAuscultation is the term for listening to the internal sounds of the body, usually using a stethoscope...
(with stethoscopeStethoscopeThe stethoscope is an acoustic medical device for auscultation, or listening to the internal sounds of an animal body. It is often used to listen to lung and heart sounds. It is also used to listen to intestines and blood flow in arteries and veins...
) - bruitBruitBruit is the term for the unusual sound that blood makes when it rushes past an obstruction in an artery when the sound is auscultated with the bell portion of a stethoscope.The term "bruit" simply refers to the sound...
("rushing" sound) on affected side, inferior of the costal marginCostal marginThe costal margin, sometimes referred to as the costal arch, is the medial margin formed by the false ribs and one true rib -- specifically, from the seventh rib to the tenth rib.... - captopril challenge testCaptopril challenge testThe captopril challenge test is a non-invasive medical test that measures the change in renin plasma-levels in response to administration of captopril, an angiotensin converting enzyme inhibitor. It is used to assist in the diagnosis of renal artery stenosis...
- captopril test dose effect on the differential renal function as measured by MAG3 scan.
- renal artery arteriogramAngiogramAngiography or arteriography is a medical imaging technique used to visualize the inside, or lumen, of blood vessels and organs of the body, with particular interest in the arteries, veins and the heart chambers...
A clinical prediction rule
Clinical prediction rule
A clinical prediction rule is type of medical research study in which researchers try to identify the best combination of medical sign, symptoms, and other findings in predicting the probability of a specific disease or outcome....
is available to guide diagnosis.
Etiology
Atherosclerosis is the predominant cause of renal artery stenosis in the majority of patients, usually those with a sudden onset of hypertension at age 50 or older. Fibromuscular dysplasiaFibromuscular dysplasia
Fibromuscular dysplasia, or fibromuscular dysplasia of arteries, often abbreviated as FMD, is a disease that can cause narrowing of arteries in the kidneys, the carotid arteries supplying the brain, and, less commonly, the arteries of the abdomen...
is the predominant cause in young patients, usually females under 40 years of age. A variety of other causes exist. These include arteritis
Arteritis
Arteritis is inflammation of the walls of arteries, usually as a result of infection or auto-immune response.-Types:Some disorders have arteritis as their main feature...
, renal artery aneurysm
Aneurysm
An aneurysm or aneurism is a localized, blood-filled balloon-like bulge in the wall of a blood vessel. Aneurysms can commonly occur in arteries at the base of the brain and an aortic aneurysm occurs in the main artery carrying blood from the left ventricle of the heart...
, extrinsic compression (e.g., neoplasms), neurofibromatosis, and fibrous bands.
Pathophysiology
The macula densaMacula densa
In the kidney, the macula densa is an area of closely packed specialized cells lining the wall of the distal tubule at the point of return of the nephron to the vascular pole of its parent glomerulus, ....
of the kidney senses a decreased systemic blood pressure owing to the reduced blood flow through the narrowed artery. The response of the kidney to this perceived decreased blood pressure is activation of the renin-angiotensin aldosterone system
Renin-angiotensin system
The renin-angiotensin system or the renin-angiotensin-aldosterone system is a hormone system that regulates blood pressure and water balance....
, which normally counteracts low blood pressure but in this case leads to hypertension (high arterial blood pressure). The decreased perfusion pressure (caused by the stenosis) leads to decreased blood flow (hypoperfusion) to the kidney and a decrease in the GFR. If the stenosis is longstanding and severe the GFR in the affected kidneys never increases again and (prerenal) renal failure
Renal failure
Renal failure or kidney failure describes a medical condition in which the kidneys fail to adequately filter toxins and waste products from the blood...
is the result.
Atherosclerotic renal artery stenosis
It is initially treated with medications. These include statins, antiplatelet agents and drugs for control of blood pressure. When high-grade renal artery stenosis is documented and blood pressure cannot be controlled with medication, or if renal function deteriorates, invasive procedure may be resorted to. The most commonly used invasive procedure is angioplastyAngioplasty
Angioplasty is the technique of mechanically widening a narrowed or obstructed blood vessel, the latter typically being a result of atherosclerosis. An empty and collapsed balloon on a guide wire, known as a balloon catheter, is passed into the narrowed locations and then inflated to a fixed size...
with or without stent
Stent
In the technical vocabulary of medicine, a stent is an artificial 'tube' inserted into a natural passage/conduit in the body to prevent, or counteract, a disease-induced, localized flow constriction. The term may also refer to a tube used to temporarily hold such a natural conduit open to allow...
ing. A 2003 meta-analysis
Meta-analysis
In statistics, a meta-analysis combines the results of several studies that address a set of related research hypotheses. In its simplest form, this is normally by identification of a common measure of effect size, for which a weighted average might be the output of a meta-analyses. Here the...
found that angioplasty was safe and effective in this context, however 7 randomized, controlled trials have not shown any clinical benefit to improve blood pressure or renal function. This includes the ASTRAL trial of 2010, although it was known to have only enrolled patients who would not "clearly" benefit from renal revascularization. There are three other ongoing clinical trials comparing medical management and angioplasty with stenting which include the CORAL trial which is scheduled to report results in early 2011. In addition to angioplasty, surgical revascularization of the renal artery is the "gold standard" and when compared to angioplasty and stenting (RAOOD trial) was found to be equivalent in morbidity and mortality. If all else fails and the kidney is thought to be worsening hypertension and revascularization with angioplasty or surgery doesn't work, then removing the "bad" kidney (nephrectomy) may improve high blood pressure dramatically.
Fibromuscular dysplasia
Angioplasty with or without stenting is the best option for the treatment of renal artery stenosis due to fibromuscular dysplasiaFibromuscular dysplasia
Fibromuscular dysplasia, or fibromuscular dysplasia of arteries, often abbreviated as FMD, is a disease that can cause narrowing of arteries in the kidneys, the carotid arteries supplying the brain, and, less commonly, the arteries of the abdomen...
.