An embolus is a solid particle, usually a fragment of clotted blood or a piece of plaque (fatty deposit), that is carried along in your bloodstream. The embolus may be very small, but because arteries divide into successively smaller vessels - first arterioles, then capillaries - eventually the embolus can go no farther. At that point, it creates an embolism, or blockage, that prevents the tissues in the affected area from getting an adequate blood supply. The embolus may originate in your heart, because of a heart attack or some other heart disorder. It may be a fragment of bacterial growth resulting from bacterial endocarditis . In rare cases, it may even be a tiny foreign object that entered an artery through a wound.

The severity of an arterial embolism depends on its size and location. The parts of the body that are most commonly affected are the brain and legs. But embolisms can occur anywhere in your body.

What are the Symptoms?

An embolism in an internal organ usually goes unnoticed unless it affects a large area. It may cause loss of function in part of the intestine, however, and cause the same symptoms as intestinal obstruction . For the symptoms of cerebral embolisms, read the articles on stroke and transient ischemic attacks. In other parts of the body, particularly the limbs, pain may be the earliest symptom. This is followed by a tingling or prickling sensation and the affected area eventually becomes numb, weak and cold. If the embolism is in an arm or leg, the skin is pale at first but later turns bluish from lack of oxygen. Both legs may be affected if a large embolus blocks the arteries at the bottom of your back, where the aorta (the main artery from your heart to your body) divides in two. Such embolisms, which are called saddle embolisms, can cause severe pain in your abdomen and in your back as well as in your legs.

What are the Risks?

If one of your major arteries is blocked, the tissues it supplies will die within hours if the blockage is not treated; in other words, dry gangrene will set in. In the brain the result of an embolism can be a fatal stroke. If you have blockage in your aorta (for example, a saddle embolism) you have only a 50 per cent chance of surviving.

The more extensive and severe the symptoms, the more quickly you should consult your physician, who will probably make a swift diagnosis without special tests. Your physician may want you to have diagnostic arteriography, however.

What is the Treatment?

Self-help: If the symptoms are in an arm or leg, you should keep the affected limb cool and immobile until medical help arrives. This reduces the need for oxygen. No self-help is possible for embolisms in any part of the body other than the limbs.

Professional help: Minor embolisms are usually treated with vasodilator drugs or aspirin. If your case is severe, you may be given an analgesic to relieve the pain and injections of an anticoagulant drug to prevent further clotting. Additional treatment of the disorder depends on the location and the size of the embolism.

In most cases when an arterial embolism severely affects an arm or leg, immediate surgery is necessary to prevent gangrene . The operation, which is called an embolectomy, involves inserting a tube into the artery and mechanically sucking the embolus out through it. If this is done in time, complete recovery is possible.