After knee replacement, dog’s lick is too ick

DEAR DR. ROACH » I had bilateral knee replacement two months ago, and I’m concerned about infections. My doctor wants me to take an antibiotic before any dental procedure, including cleaning, which I will do. I also have a dog that loves to lick any cuts, especially if there is some blood to lick. What are the chances of a prosthesis becoming infected? Can one’s immune system fight off any bacteria that gets into the bloodstream? DEAR READER » I often have heard that dogs’ mouths are clean, but that is not the case. Bacteria from a dog’s mouth can indeed cause an infection in any kind of open wound, even a small cut or scratch. Our immune system is normally very good at fighting them off, and I rarely see significant infections caused by the germs in a dog’s mouth (cats, monkeys and humans tend to be much worse).

However, in an artificial joint, such as after a knee or hip replacement, the immune system can’t effectively fight off infection, which is why your doctor recommended the antibiotic before a dental cleaning. They often cause some bacteria to transiently enter the bloodstream. Bacteria can enter the blood through an infected wound as well.

The chances of a joint infection after a dental cleaning or a cut, with or without a dog, are small, but the event is devastating. Keep the dog away: Cleanse any wound thoroughly with mild soap and water — but no harsh disinfectants like peroxide, which do more harm than good. Apply some antibiotic ointment (such as triple antibiotic) and cover with a clean bandage.

DEAR DR. ROACH » Would you give me information on blocked bowel movements? I had a colonoscopy two years ago, and they said they couldn’t complete the procedure because of bowel blockage. I am 86 years old and don’t want a colostomy. DEAR READER » A bowel blockage or obstruction can be partial or complete. There are numerous causes of bowel obstructions. Cancer is the first one I think of, as it’s the worst case, but others include a volvulus (twisting of the bowel on its axis) and intussusception (folding in on itself like a sock).

Symptoms of a bowel obstruction include pain and abdominal fullness, and, paradoxically, can include diarrhea. This is because the part of the bowel beyond the level of obstruction can secrete fluid and mucus, confusing the fact that there is an obstruction. A complete bowel obstruction is a surgical emergency, and there is a surgical maxim that “the sun never sets on a bowel obstruction” — i.e., immediate surgery is life-saving. Clearly, you did not have a complete bowel obstruction, and I am convinced that there was a miscommunication at the time of your colonoscopy two years ago. If they were concerned about a serious or worsening obstruction, they would have recommended additional tests or procedures, such as a CT scan or evaluation by a surgeon.

It’s hard for me to guess what it is they meant. I wonder if the preparation they gave you for the colonoscopy wasn’t adequate to clean the bowel completely, and they had a hard time getting to the whole colon. I spoke with a gastroenterologist, Dr. Doug Weine, and he thought that you might have a stricture (narrowing in the colon) due to diverticular disease or tortuous, redundant colon (excess bends and a longer-than-average length).

In any event, two years is too long to wait and worry about your colon health. Get back to the doctor who did the colonoscopy, and get a complete exam done.

Contact Dr. Roach at ToYourGoodHealth@med. cornell.edu.