Fistulas

What are intestinal fistulas?

Intestinal fistulas are tubular connections between the bowel and other organs or the skin. Fistulas form when inflammation extends through all of the layers of the bowel and then proceeds to tunnel through the layers of other tissues. Accordingly, fistulas are much more common in Crohn's disease than in ulcerative colitis. (In the latter, as you recall, the inflammation is confined to the inner lining of the large intestine.) Fistulas often are multiple. They may connect the bowel to other loops of the bowel (enteroenteric fistulas), to the abdominal wall (enterocutaneous), to the skin around the anus (perianal), and to other internal locations such as the urinary bladder (enterovesical), vagina (enterovaginal), muscles, and scrotum.
In Crohn's disease patients, fistulas may form in conjunction with intestinal strictures. One reason for this association is that both fistulas and strictures can begin with inflammation of the entire thickness of the bowel wall (transmural inflammation). Subsequent scarring (fibrosis) causes strictures while continuing inflammation and tissue destruction leads to the fistulas. A stricture can also help create a fistula. As already mentioned, a perforation of the intestine can occur above an obstructing stricture. The perforation can create a tract outside of the bowel wall. A fistula then may develop in this tract.

What symptoms do fistulas cause and how are they diagnosed and treated?

Intestinal fistula symptoms
Some fistulas, especially those that connect adjacent loops of bowel, may not cause significant symptoms. Other fistulas, however, can cause significant abdominal pain and external drainage, or create a bypass of a large segment of intestine. Such a bypass can occur when a fistula connects one part of the bowel to another part that is further down the intestinal tract. The fistula thereby creates a new route for the intestinal contents. This new route bypasses the segment of intestine between the fistula's upper and lower connections to the intestine. Sometimes, fistulas can open and close sporadically and unevenly. Thus, for example, the outside of a fistula might heal before the inside of the fistula. Should this occur, the bowel contents can accumulate in the fistulous tract and result in a pocket of infection and pus (abscess). An abscess may be quite painful and can be dangerous, especially if the infection spreads to the bloodstream.
Intestinal fistula diagnosis
Fistulas sometimes are difficult to detect. Although the outside opening of a fistula may be simple to see, the inside opening that is connected to the bowel may not be easy to locate. The reason for this difficulty is that fistulas from the bowel can have long, winding tunnels that finally lead to the skin or an internal organ. Endoscopy might detect the internal opening of a fistula, but it can easily be missed. Sometimes, a small bowel barium X-ray will locate a fistula. Often, however, an exam under general anesthesia may be required to fully examine areas that have fistulas, especially around the anus and vagina.
Intestinal fistula treatment
Intestinal fistulas that do not cause symptoms often require no treatment. Fistulas that cause significant symptoms, however, usually require treatment, although they are frequently difficult to heal.
Fistulas located around the anus (perianal) sometimes can be improved by treatment with the antibiotics, metronidazole (Flagyl) or ciprofloxacin (Cipro). In response to the antibiotics, some of these fistulas even close completely. Also, treatment with the immunosuppressive medications, azathioprine or 6MP, improves fistulas located around the anus (perianal) in almost two thirds of patients, including complete healing in one third. More recently, the new drug infliximab (Remicade), which is an antibody to one of the body's inflammation-inducing chemicals, has been shown to produce very similar results. Remember, however, that infliximab might worsen strictures, which, as mentioned, can sometimes be associated with fistulas.
When medications for the treatment of fistulas are discontinued, they usually re-open within 6 months to a year. Steroids do not heal fistulas and should not be used for this purpose. Other medications that suppress the immune system, such as cyclosporine or tacrolimus (FK506 or Prograf), are currently being studied for the treatment of fistulas. Sometimes, resting the bowel by feeding the patient solely with total parenteral (intravenous) nutrition (TPN), is required to treat fistulas. Even if these fistulas heal in response to the TPN, they commonly recur when eating is resumed.
Fistulas sometimes require surgery. For example, when fistulas around the anus become very severe, they can interfere with the patient's ability to control bowel movements (continence). In this situation, the surgeon might make an opening (ostomy) to the skin from the bowel above the fistulas. The intestinal contents are thereby diverted away from the fistulas. Occasionally, when absolutely necessary, intestinal fistulas are surgically removed, usually along with the involved segment of the bowel. Fistulas from the intestine to the bladder or vagina are frequently very difficult to close with medical treatment alone and often require surgery.

What are fissures and how are they treated?

Fissures are tears in the lining of the anus. They may be superficial or deep. Fissures are especially common in Crohn's disease. They differ from fistulas in that fissures are confined to the anus and do not connect to other parts of the bowel, other internal organs, or the skin. Still, fissures can cause mild to severe rectal pain and bleeding, especially with bowel movements. The most common treatment for anal fissures is periodic sitz baths or topical creams that relax the muscle (sphincter) around the anus. Injections of tiny amounts of botulinum toxin into the muscles around the anus have been reported to be helpful in relaxing the sphincter, thereby allowing the fissures to heal. The benefit of this type of therapy, however, is still controversial. Sometimes, surgery is needed to relieve the persistent pain or bleeding of an anal fissure. For example, the surgeon may cut out (excise) the fissure. Alternatively, the muscle around the anus can be cut (sphincterotomy) to relax the sphincter so that the fissure can heal. However, as is the cases with any surgery in patients with Crohn's disease, post-operative intestinal complications can occur frequently.

What is small intestinal bacterial overgrowth (SIBO)?

Small intestinal bacterial overgrowth (SIBO) can occur as a complication of Crohn's disease but not of ulcerative colitis since the small intestine is not involved in ulcerative colitis. SIBO can result when a partially obstructing small bowel stricture is present or when the natural barrier between the large and small intestines (ileocecal valve) has been surgically removed in Crohn's disease. Normally, the small bowel contains only few bacteria, while the colon has a tremendous number of resident bacteria. If a stricture is present or the ileocecal valve has been removed, bacteria from the colon gain access to the small bowel and multiply there. With SIBO, the bacteria in the small bowel begin to break down (digest) food higher up than normal in the GI tract. This digestion produces gas and other products that cause abdominal pain, bloating, and diarrhea. In addition, the bacteria chemically alter the bile salts in the intestine. This alteration impairs the ability of the bile salts to transport fat. The resulting malabsorption of fat is another cause of diarrhea in Crohn's disease. (As previously mentioned, inflammation of the intestinal lining is the most common cause of diarrhea in patients with IBD.)

SIBO diagnosis

SIBO can be diagnosed with a hydrogen breath test (HBT). In this test, the patient swallows a specified amount of glucose or another sugar called lactulose. If bacteria have reproduced in the small bowel, the glucose or lactulose is metabolized by these bacteria, which causes the release of hydrogen in the breath. The amount of hydrogen in the breath is measured at specific time intervals after the ingestion of the sugar. In a patient with SIBO, the hydrogen is eliminated into the breath sooner than the hydrogen that is produced by the normal bacteria in the colon. Accordingly, the detection of large amounts of hydrogen at an early interval in the testing indicates the possibility of SIBO. Another test, which may be more specific, uses a sugar called xylose. In this test, the swallowed xylose is tagged with a very small amount of radioactive carbon 14 (C14). The C14 is measured in the breath and interpreted by applying the same principles as used for hydrogen in the HBT.

SIBO treatment

The best treatment for bacterial overgrowth is antibiotics for approximately 10 days using, for example, neomycin, metronidazole, or ciprofloxacin. After this treatment, the breath test may be repeated to confirm that the bacterial overgrowth has been eliminated. SIBO may recur, however, if the stricture itself is not treated, or if the bacterial overgrowth is due to the surgical removal of the ileocecal valve.