DEAR DR. ROACH: I have a colonoscopy scheduled for mid-May. I spoke with the physician assistant, and she read me the warnings about possible punctures and possible bleeding afterward. With a puncture, she said a colostomy bag is required for three to four months. If there’s bleeding afterward, they must go back into the colon to stop it.

She did not say what the frequency was for these two issues, and now I am having great anxiety about having the procedure. I’m not aware of a history of colon cancer in my family. I did have a benign polyp removed five years ago during my first colonoscopy, and that’s why I am repeating the test within a five-year time span. Why isn’t there a blood test that can determine if one has colon cancer? – B.B.

ANSWER: Colonoscopy does have risks like any medical procedure, but those risks are low. If someone does not require biopsy of a suspicious colon, the risk of bleeding is less than one person per 1,000. If a polyp is removed, bleeding happens in about 1% to 2% of people and can usually be controlled by the physician performing the endoscopy, by using a clip or injecting medication to stop the bleeding. Delayed bleeding occasionally requires a second colonoscopy — this happens most commonly after the removal of a large polyp. Despite thousands of my patients getting screening colonoscopies, I cannot recall ever having a patient require a second colonoscopy.

Perforation (“puncture”) occurs in approximately one person per 10,000 in experienced colonoscopy screening centers. I have seen a few cases, and most often the perforation will heal itself in the following 24 hours. A surgery so extensive that requires a diverting colostomy after colonoscopy would be extremely rare.

Most physicians know the risks and have seen the outcomes and choose colonoscopy for themselves as the best screening test for colon cancer. I did for myself. In the future, blood tests may be developed that are more accurate. The blood tests for colon cancer that exist now are hardly ever used, since there are many better options.

If you decide against colonoscopy, a test that uses immunochemical and DNA technology is the next best screening test for cancer; however, if the test is positive, a colonoscopy would certainly then be needed to make a definitive evaluation.

DEAR DR. ROACH: Between my breasts, there is what appears to be a bone that protrudes. Could you tell me what that could be? I don’t have a doctor right now. – B.P.

ANSWER: About once every year or two, someone comes to see me with this exact question. At the end of the sternum (also called the breastbone), there is a small triangular piece of cartilage called the xiphoid process. In some people, it curves outward and can press the skin and muscle tissues slightly so that it protrudes a bit. Although we all were born with this cartilage, it can become harder and calcified during adult life, making it seem more prominent. It is nothing to be concerned about.

I hope you find a new doctor soon.

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.