10 Hospital Physician Board Review Manual www.turner-white.com
to medical therapies, surgical intervention is indi-
PERIANAL AND FISTULIZING CD
Up to half of CD patients will develop a fistula.
Approximately 50% of CD fistulae are perianal,
25% are enteroenteric, 10% are enterovaginal,
and the remainder are accounted for by entero-vesical, enterocutaneous, or other less common
types of fistulae.39 When development of a fistula is suspected, carefully defining the anatomy
through imaging is important for successful management. In evaluation of perianal fistulae, examination under anesthesia (EUA) is considered the
gold standard for diagnosis and has the advantage
that surgical intervention can be performed during the procedure for abscess drainage or seton
placement. Pelvic MRI and endoscopic ultrasound
(EUS) are also effective in the evaluation of perianal fistulae, with accuracies of 76% to 100% and
56% to 100%, respectively. EUA and one of these
imaging techniques also provide complementary
information, so the ideal approach is to perform
imaging followed by EUA. A perianal fistula is considered simple when it is low (superficial, low inter-sphincteric or low intra-sphincteric), has a single
external opening, is not associated with abscess,
is not connected to other organs, rectal or anal
stenosis is not present, and proctitis is not present.
Otherwise, the fistula is considered complex.
Simple fistulae can be managed medically. An-
tibiotics, azathioprine, 6-MP, methotrexate, and
anti-TNF agents have been used successfully.
Metronidazole and ciprofloxacin have both been
studied and have been shown to decrease fistula
drainage, but typically do not promote fistula clo-
sure over a 6- to 8-week course of treatment.40
A meta-analysis of thiopurines in treatment of CD
showed that treatment with azathioprine or 6-MP
resulted in improvement in 54% of patients versus
21% of patients in placebo groups.41 Infliximab has
been shown to be effective in medically refractory
perianal fistulizing disease, where 55% of patients
receiving infliximab achieved closure (versus de-
creased drainage) of fistulae versus 13% in the
placebo group.42 This efficacy is likely a class
effect, as other anti-TNF agents have also been
shown to be effective. Cyclosporine, tacrolimus,
and thalidomide have also been reported to be
effective for the management of perianal fistulizing
disease, although their use is much less common
and only recommended for clinicians with experi-
ence in appropriate therapeutic monitoring.
Surgical intervention should be considered in
the case of complex fistulae, but is not always necessary. Ideally, a combined medical and surgical
approach is pursued and can improve outcomes.
Surgical interventions may include abscess drainage and seton placement. Fistulectomy is no longer commonly performed because of poor healing
and high rates of incontinence. Refractory cases
may be treated by placement of a diverting ostomy
or even proctectomy. Topical treatments including
fibrin glue, fibrin plugs, topical tacrolimus, and intra-lesional infliximab have been reported as potential
therapeutic options in the management of fistulizing
perianal CD, but are not commonly used.
Unlike in UC, surgical resection of affected segments of bowel is not curative in CD. Indications for
surgery in CD include refractory disease, persistent
or recurrent obstruction, abscess, refractory fistula, strictureplasty, dysplasia, malignancy, perforation, or hemorrhage. In severe disease, surgery
should be strongly considered after 7 to 10 days
of intensive inpatient therapy with inadequate response to medical or conservative therapy.