Inflammatory Bowel Disease: Intestinal Problems (cont.)
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?
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.
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.
How are fistulas in IBD treated?
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.
Next: What are fissures and how are they treated? »
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