DEAR DR. ROACH: What could precipitate a need to check an 83-year-old man’s carotid arteries for blockage? What percentage of blockage would necessitate surgery? – W.M.

ANSWER: There are two carotid arteries, running on either side of the neck, bringing blood to the head. They provide a great deal of the blood flow to the brain, and blockages of either can lead to a stroke.

The symptoms that would make a doctor want to check for blockages in the artery are stroke and transient ischemic attack. TIA is a loss of blood and oxygen flow in the brain, leading to temporary symptoms that look very like a stroke.

If, when checked, the carotid artery has blockages on the same side that the TIA or stroke was on, then not only is medical therapy begun to reduce risk of another event, but surgery is considered as well. If the blockage is not very extensive, surgery is not any more beneficial than medical therapy, including dietary changes and exercise counseling. However, for more extensive blockages, surgery can help. Men have been proven to see a benefit when the artery is 50% to 99% blocked; with women, only those with 70% to 99% blockages benefit from surgery.

The short-term risk of dying from the surgery is significant. In large studies, the overall risk was just about 3%, although newer surgical techniques may have brought that number down a bit since those studies were published in the 1990s. Carotid surgery is not to be undertaken lightly, especially since medical therapy is much better than it used to be as well. There are newer and more powerful drugs to reduce the risk of stroke. Surgery should be considered only in someone who is pretty healthy otherwise and who is likely to live at least five more years, since the risk of dying around the time of surgery is significant.

I do not recommend screening for blockages in the carotids in people with no symptoms. It’s more important to identify people who are at risk for stroke and reduce that risk by better lifestyle and medications if needed.

DEAR DR. ROACH: My doctor wants me to have a colonoscopy, but I would have to be off Xarelto for five days! The last time I did this I had a small stroke! – P.D.

ANSWER: Xarelto is an anticoagulant, used in people who are at high risk for developing a blood clot. This may include a previous history of a blood clot in the legs or lungs, atrial fibrillation, mechanical heart valves or other reasons.

For people with a high risk of complications if an anticoagulant is stopped, most experts recommend performing a screening colonoscopy without stopping the anticoagulation. However, if the colonoscopy is being performed to remove a large polyp, for example, then there is a significant risk of bleeding if the anticoagulant isn’t stopped. In these cases, the risk of bleeding must be weighed against the risk of a clot, which can cause a stroke.

I am surprised at the length of time you mention. Five days is usually not necessary with rivaroxaban (Xarelto) and similar medicines. The most recent paper I read suggested that restarting the next day is generally safe for most people after a polyp removal.

Ask the gastroenterologist performing your colonoscopy to talk with the doctor prescribing the Xarelto, so they can consider all the risks and recommend the best course.

Dr. Roach regrets that he is unable to answer individual letters, but will incorporate them in the column whenever possible. Readers may email questions to ToYourGoodHealth@med.cornell.edu or send mail to 628 Virginia Dr., Orlando, FL 32803.