Fibromuscular Dysplasia

1 What is Fibromuscular Dysplasia?

Fibromuscular dysplasia is a medical condition in which there is stenosis (narrowing ) and aneurysm (enlargement) of the medium-sized arteries of the body.The areas of narrowing and enlargement are next to each other. The arteries become narrow because the muscle and fibrous tissues in the arteries thicken. The narrowing of the arteries can cause a decrease in the blood flow to organs causing an impairment in organ function.

Fibromuscular dysplasia mostly occurs in the arteries that lead to the kidneys, brain, abdomen, arms and legs. Although there is no cure for fibromuscular dysplasia, it can be treated effectively. If it is left untreated, complications like high blood pressure and tears of arteries may occur.

Fibromuscular dysplasia affects more women than it affects men. This may be explained by the changes in the levels of hormones especially during pregnancy.

2 Symptoms

The majority of people with fibromuscular dysplasia do not have any symptoms. If symptoms are present, they may vary depending on the artery that is affected. Symptoms may include:                                                                                    

-If the kidneys are affected ; high blood pressure, damage of the kidney tissue (ischemic renal atrophy) and rarely kidney failure.

-If the arteries are are going to the brain e.g. carotid arteries are affected ; headache, dizziness, blurred vision, temporary loss of vision, pulsating ringing in the ears (tinnitus), neck pain, weakness or numbness of the face.                                            

-If arteries supplying the abdomen are affected ; abdominal pain especially after eating and loss of weight.                            

-If the arteries leading to the arms or legs are affected ; cold extremities, weakness, numbness and changes in the appearance or color of the skin.

In most cases of fibromuscular dysplasia more than one artery is affected.

3 Causes

The exact cause of fibromuscular dysplasia is not known. However, genetic factors and hormonal imbalances have been shown to cause fibromuscular dysplasia. People with abnormally formed arteries have a higher risk of having fibromuscular dysplasia.

4 Making a Diagnosis

Doctors usually check for other diseases that cause the arteries to narrow, like atherosclerosis, before they can diagnose fibromscular dysplasia. The tests used include physical examination and blood chemistry to evaluate the amount of glucose and cholesterol in the blood.                                                                                                                                          

Tests that help doctors to diagnose fibromuscular dysplasia include:                                                                                

-Catheter-based angiography,in which a thin tube is inserted into one of the arteries ,like the femoral artery, and moves until it reaches the artery that the doctor wants to examine. A dye is injected into the tube and X-ray images can be used to examine the artery.                                                                                                                                                            

-Doppler ultrasound,a transducer that is pressed on the skin is used to send sound waves into the body.e sound waves bounce off red blood cells and the ultrasound can estimate the speed of blood. In fibromuscular dysplasia, blood moves slowly through the arteries.                                                                                                                                                          

-Computerized Tomography (CT) angiography, doctors are able to see if arteries are narrowed or blocked. A dye is injected into an artery and then X-ray images of the artery that the doctor suspects are made.

-Magnetic Resonance Imaging  (MRI) , a test that allows doctors to view soft tissues. Patients lie in a long tube-like machine that uses a magnetic field and radio waves to capture images of the soft tissues of the body. The cluster of cells causing narrowing can be seen when  MRI is used as a diagnostic test.

5 Treatment

There are several treatment options for fibromuscular dysplasia. They include medical procedures, surgery and medications. The method of treatment depends on the patients state of health, the location of the affected artery and presence of any other diseases.

Medical procedures and surgery are usually recommended if the patient is in a good state of health. In this treatment method, the affected artery is repaired and thus blood supply is improved also. The following procedures are used to repair blood vessel:

-Percutaneous transluminal renal angioplasty (PTRA); it is usually performed at the same time as the catheter-based angiogram. If a narrow area of the artery is seen on the angiogram, a wire is threaded into the artery and a catheter with a balloon is inserted into the narrowed area.The balloon is then inflated to open the narrowed part of the artery. This procedure takes one to two hours and patients are usually given sedatives to keep them calm.

-Surgical revascularization. This procedure is more invasive than PTRA and is mostly performed in severe cases of fibromuscular dysplasia. General anesthesia is required in this procedure.                                                                                     Patients who have aneurysms require surgery in which a metal mesh (stent ) is placed over the weakened part of the artery. This helps to prevent it from rupturing.                                                                                                                  

Because there is narrowing and bulging of arteries in patients with fibromuscular dysplasia, there is an increased risk of these high blood pressure. Therefore medications that are used to treat high blood pressure are also given to these patients. These drugs include;

-Beta blockers like metoprolol (Lopressor, Toprol-XL) which slow down the heart beat

-Angiotensin-converting enzyme (ACE)  inhibitors like enalapril (Vasotec) and benazepril (Lotensin), that prevent blood vessels from narrowing.

-Angitensin II receptor blockers that help relax blood vessels by blocking the action of a natural chemical that narrows blood vessels. They include candesartan (Antacand) and losartan (Cozaar).                                                                              

-Diuretics which help by  reducing  the volume of blood by increasing the excretion of water through the kidneys. An example of a diuretic is hydrochlorothiazide (Macrozide)

-Calciom channel blockers. These drugs reduce blood pressure by causing blood vessels to relax. Examples are  amlodipine (Norvasc) and nifedipine (Procardia).

6 Prevention

There is no effective method that can be used to prevent fibromuscular dysplasia. However, quitting smoking can help to reduce the risk of having this condition.

7 Risks and Complications

Women and old people are at a higher risk of having fibromuscular dysplasia. People who smoke have also been shown to be at risk.

The main complications associated with fibromuscular dysplasia include:

  • hypertension (high blood pressure), occurs due to the narrowing of arteries. It can lead to heart or kidney failure.
  • chronic kidney failure
  • dissected artery ( tears in the walls of the arteries), this can reduce blood flow to an organ that is supplied by the injured artery.
  • aneurysms, these are areas in the wall of the arteries that are weak and bulge out. Life-threatening emergencies can occur if the aneurysm bursts.
  • stroke, this is a condition in which there less blood is flowing to the brain. It can occur due to narrowing or capturing of the ves.
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