Introduction:
Fibrous dysplasia is an uncommon condition of the blood vessels that is seen in 10 to 20 percent of women in the younger population. Fibromuscular dysplasia occurs as a non-inflammatory condition that is idiopathic in origin and non-atherosclerotic in type. Fibromuscular dysplasia of the blood vessels supplying the kidneys often manifests an increase in pressure in the arteries supplying the kidneys. Although this condition may affect several areas of different arteries, it is commonly seen affecting the arteries of the heart and kidney. The reason that this condition is important is because of its potential to cause strokes in younger populations.
What Are the Factors That Cause Fibrous Dysplasia of the Renal Artery?
Despite conducting multiple studies over time, the exact cause of the disease is not known. However, the most common factors that are associated with renal fibrous dysplasia are seen in identical twins and in patients with a familial history that is detected with a renal angiogram (a diagnostic procedure done to study the blood vessels and their circulation). The other factors associated are polymorphism of the gene showing renin-angiotensin mechanism, smoking, kidney transplant, and more incidence in the right kidney compared to the left. Fibrous dysplasia of the renal artery is also seen in association with syndromes like tuberous sclerosis, Marfan's syndrome, Alport syndrome, pheochromocytoma, medullary sponge kidney, cystic medial necrosis, coarctation of the aorta, Eisenstein-Danlos syndrome, and alpha-1 antitrypsin deficiency.
How Commonly Is Renal Artery Fibromuscular Dysplasia Seen?
Fibromuscular dysplasia is commonly seen in younger patients below the age of fifty. The incidence of other conditions associated with them is around two to six percent in patients who have undergone cardiac diseases. The prevalence is seen more in females than in men in a ratio of 3:1, with a more global incidence seen in France. The condition is bilaterally seen in almost fifteen percent of the patients.
How Does Fibromuscular Dysplasia of the Renal Artery Occur?
Although the condition is idiopathic, many medical conditions predispose to a previous history of arterial stenosis, which eventually leads to a tear or incompetency in the vessel wall. That gradually develops into a fistula, compromising the efficacy of the arteries and their function. The other predisposing factors include obesity, smoking, a long-term history of increased blood pressure, etc.
How Is Fibromuscular Dysplasia of the Renal Artery Seen Clinically?
Fibromuscular dysplasia of the renal artery is one of the most common presentations and is seen in the following ways:
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Tears in the arteries supplying the kidneys.
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Blood is in urine.
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Flank pain - It is a pain experienced at the junction between the ribs and the abdomen.
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Abdominal Bruit - It is a swishing sound heard in the arteries during diastole or systole, commonly seen in the iliac arteries.
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Hypokalemia (decrease in serum potassium) is associated with hyperaldosteronism (a clinical condition occurring due to increased production of aldosterone).
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Ischemic Nephropathy - Ischemic nephropathy characterized by a lack of blood supply to the kidneys due to the blockage of arteries supplying the kidneys.
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Renal Infarct - Renal infarct is characterized by the blockage of arteries supplying the kidneys.
How Is Fibromuscular Dysplasia of the Renal Artery Diagnosed Clinically?
The fibrous dysplasia of the renal artery can be diagnosed using the following:
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Duplex Ultrasonography: This is the first-line screening test used for FMD. Ultrasonography is a procedure done to assess the blood flow in the vesicles by recording the sound of it. The presence of FMD is indicated by duplex ultrasound findings of turbulence during blood glow, tortuosity, increased velocities, and the resistance capacity of the mid and distal arteries to withstand force. However, duplex ultrasonography is a technique-sensitive and operator-dependent procedure.
- Magnetic Resonance Angiography: Magnetic resonance imaging (MRA) is a three-dimensional imaging technique used to assess the muscles and provides equivalent sensitivity and specificity without the danger of radiation exposure or contrast nephropathy. However, this procedure is contraindicated for patients with severe renal failure. Recent studies demonstrate that the MRA has ninety-seven percent sensitivity and around ninety-three percent specificity compared to conventional angiography.
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Arteriography: This arteriography procedure is a gold standard test used for diagnosing FMD, as it helps in determining the level of pressure across the areas that show narrowing of the artery. Where any narrowing that shows a significant alteration in the blood flow is defined as a pressure gradient that is greater than ten percent, this catheter-based angiography is not only better than conventional imaging, but it also allows for endovascular treatment (performing surgical procedures on the blood vessels without opening up the entire area). Modern techniques that involve intravascular ultrasonography may improve angiography and help in determining the reciprocation of stenosis after angioplasty.
How Is Fibromuscular Dysplasia of the Renal Artery Treated?
The management of renal artery fibrous dysplasia can be done after assessing blood pressure, any potential risk factors, and the chances of ischemia. The management of fibromuscular dysplasia of the renal artery is treated depending on the duration of the condition; in the case of acute renal artery fibrous dysplasia, the condition is managed medically, whereas intensive treatments are required for chronic conditions that include both surgical and medical management followed by postoperative care.
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Medical Management: The medicines of choice that are prescribed for renal artery fibrous dysplasia are antihypertensives that reduce blood pressure, like angiotensin-2 receptor blockers, angiotensin-converting enzyme inhibitors, calcium channel blockers, and beta blockers, and medicines that reduce the load on the kidneys, like diuretics. However, conducting periodic testing of the blood and urinary outcomes is important.
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Surgical Management: Depending on the intensity of the disease, there are often two types of surgeries that are preferred, and they are:
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Revascularization Surgery: This is a surgical procedure done to alter or replace the torn or damaged artery. However, this condition is rarely preferred, depending on the amount and location of the damaged artery.
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Percutaneous Transluminal Angioplasty: This common term is also known as balloon surgery, where a thin, flexible tube is inserted into the narrowed canal. This catheter transports a small stent made of mesh that helps open the blocked artery.
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What Are the Conditions That Resemble Renal Artery Fibrous Dysplasia?
In a clinical scenario, it is necessary to know the conditions that closely resemble renal artery fibrous dysplasia in order to rule out other possibilities. Such conditions that resemble renal artery fibrosis are:
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Vasculitis: Vasculitis is a clinical condition that is characterized by inflammation of the blood vessels and is seen clinically as Takayasu arteritis (a rare type of inflammation of the blood vessel), polyarteritis, and vasculitides of giant cells.
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Atherosclerotic Renal Artery Stenosis: This condition has distinguishing characteristics that include older people, mostly showing associations with cardiovascular risk factors or blockage of the artery commonly seen in young females.
What Are the Complications Associated with It and the Outcome of Renal Artery Fibrous Dysplasia?
Renal fibrous dysplasia is associated with complications like increased blood pressure, tears in the arteries, bulging of the arteries, or conditions like stroke. Despite the condition being associated with multiple complications, careful management of the younger patients is indicated for a better prognosis.
Conclusion:
Although the long-term data on prognosis in fibromuscular dysplasia (FMD) are few. According to the American Heart Association, advancement in fibromuscular dysplasia is infrequent, but assessing a developing stenosis is difficult. Fibromuscular dysplasia is now described as a benign condition that was found by chance. In young females, involvement of the cranial nerves has the most non-significant outcome for the vessel. In conclusion, fibromuscular dysplasia of the renal artery can lead to deleterious side effects when the disease is left unattended or treated. Hence, it is necessary to follow an ideal treatment plan for greater benefits.
