I have a 15-year-old abdominal incision from my C-section and appendix surgery. In the last month I have gotten two pimple-like sores that discharge either blood or a milky pus-like discharge. My internist says she thinks I have a "tract." (On my bill it says cellulitis.) She prescribed Augmentin for two weeks, and I am covering the sores with Duoderm film to keep them dry. I would like more information on what a tract is. She said if it doesn't clear up in two weeks, she will refer me to a surgeon. Could you give me more information?

Marianne

You describe a very unusual case. Let me explain what some of these terms mean. First, "cellulitis" is simply a skin and soft-tissue infection. It tells us nothing about the cause. Most cases of cellulitis are due to a superficial lesion of the skin, such as a minor cut, that subsequently becomes infected with bacteria from the skin or environment. It can usually be treated with antibiotics. Sometimes, cellulitis develops from a deeper infection such as osteomyelitis, an infection of the bone.

A "sinus" or "sinus tract" is a narrow connection from a deep infection to the skin. What happens is that a deep infection develops -- be it from appendicitis, a localized bowel infection or another source. The body contains the infection, preventing it from entering the bloodstream. An abscess (collection of pus) develops that is weaker in one area. As the abscess continues to progresses, a narrow tract forms in the weak area. Eventually, the tract reaches the skin, where it ruptures. Since the pressure of the abscess is relieved, the patient may not have any fever or other general complaints. This is exactly the way chronic osteomyelitis would present. An infection in a long bone develops and progresses, sometimes over months. Eventually the infection reaches the skin, forming a sinus.

A sinus tract developing in the abdomen could have a few causes. It may be due to a deep skin infection. This is possible in your case if you had a retained a surgical suture (stitch) that somehow became infected. There may have been an infection around the suture, just an inch or so beneath the skin. This could have easily progressed to the surface, causing a sinus tract.

The other possibility is a deep abdominal infection. An infection related to your appendix would be unusual given the delay between the surgery and your current problem. I cannot discount the possibility, but I think a second source may be just as likely. One bacterial cause of a much-delayed sinus forming in the abdomen is actinomycosis. This infection, caused by bacteria called Actinomyces, presents very slowly, sometimes more like a tumor. It causes jaw infections after dental abscesses, lung infections and chest sinuses, and abdominal and pelvic infections. Months and occasionally years after a disruption of the bowel, as can occur with a ruptured appendix, the patient can develop a sinus tract to the skin. Fever, abdominal pain and weight loss can all occur.

Treatment of a sinus tract usually requires drainage of the deep infection and surgery to remove the tract. In the uncommon cases of actinomycosis, antibiotics alone for prolonged periods may be sufficient. In your case, I would have the organisms in the pus cultured (grown in the lab) to rule out actinomycosis. If you do not respond to the short course of antibiotics, I would consider a CT scan of your abdomen to make sure there is no deeper infection.