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U N I T 8
Gastrointestinal and Hepatobiliary Function
been likened to a lead pipe or rubber hose. The adja-
cent mesentery may become inflamed, and the regional
lymph nodes and channels may become enlarged.
The clinical course of Crohn disease is variable;
often, there are periods of exacerbations and remis-
sions, with symptoms being related to the location of
the lesions.
6-8,28
The principal symptoms include inter-
mittent diarrhea, colicky pain (usually in the lower right
quadrant), weight loss, fluid and electrolyte disorders,
malaise, and low-grade fever.
32
Because Crohn disease
affects the submucosal layer to a greater extent than the
mucosal layer, there is less bloody diarrhea than with
ulcerative colitis. Ulceration of the perianal skin is com-
mon, largely because of the severity of the diarrhea. The
absorptive surface of the intestine may be disrupted;
nutritional deficiencies may occur, related to the specific
segment of the intestine involved. When Crohn disease
occurs in childhood, one of its major manifestations may
be retardation of growth and physical development.
Complications.
Complications of Crohn disease
include fistula formation, abdominal abscess formation,
and intestinal obstruction. Fistulas are tubelike passages
that form connections between different sites in the gas-
trointestinal tract. They also may develop between other
sites, including the bladder, vagina, urethra, and skin.
Perineal fistulas that originate in the ileum are relatively
common. Fistulas between segments of the gastrointesti-
nal tract may lead to malabsorption, syndromes of bac-
terial overgrowth, and diarrhea. They also can become
infected and cause abscess formation.
Diagnosis andTreatment.
The diagnosis of Crohn dis-
ease requires a thorough history and physical examina-
tion. Endoscopy is used for direct visualization of the
affected areas, to determine extent of disease involvement,
and to obtain biopsies. Measures are taken to exclude
infectious agents as the cause of the disorder. This usually
is accomplished by the use of stool cultures and exami-
nation of fresh stool specimens for ova and parasites.
CT scans may be used to detect an inflammatory mass,
fistula, or abscess. Radiographic contrast studies may be
used to augment endoscopy or CT scans.
Treatment methods focus on terminating the inflam-
matory response and promoting healing, maintaining
adequate nutrition, and preventing and treating compli-
cations. Nutritional deficiencies are common in Crohn
disease because of diarrhea, steatorrhea, and other mal-
absorption problems. A nutritious diet that is high in
calories, vitamins, and proteins is recommended. Because
fats often aggravate the diarrhea, it is recommended that
they be avoided. Elemental diets, which are nutritionally
balanced but residue free and bulk free, may be given dur-
ing the acute phase of the illness.
8
These diets are largely
absorbed in the jejunum and allow the inflamed bowel to
rest. Total parenteral nutrition (i.e., parenteral hyperali-
mentation), which is administered intravenously, may be
needed when food cannot be absorbed from the intestine.
8
Several medications have been successful in sup-
pressing the inflammatory reaction in Crohn disease,
including 5-aminosalicylic acid (5-ASA) agents, cor-
ticosteroids, antibiotics, immunosuppressant drugs
(azathioprine, 6-mercaptopurine, methotrexate), and
anti–tumor necrosis factor (TNF) therapies (infliximab
and adalimumab).
8,28
The 5-ASA agents act locally to
affect multiple sites in the arachidonic acid pathway crit-
ical to the pathogenesis of inflammation. Much of the
unformulated 5-ASA is absorbed from the small intes-
tine and does not reach the distal small bowel or colon
in appreciable amounts. To overcome the rapid absorp-
tion of 5-ASA, a number of formulations (e.g., sulfasala-
zine, mesalamine) have been designed to deliver the drug
to the distal small bowel and colon. Corticosteroids are
used to suppress the acute clinical symptoms in persons
with small and large bowel disease. Metronidazole is an
antibiotic used to treat bacterial overgrowth in the small
intestine. Azathioprine, 6-mercaptopurine, methotrex-
ate, and cyclosporine are immunomodulating drugs that
are used in persons who do not respond to other forms
of therapy.
8
The anti-TNF agents are monoclonal anti-
bodies that target the destruction of TNF-
α
, a mediator
of the inflammatory response that is known to be impor-
tant in granulomatous inflammatory processes such as
Crohn disease.
8
These agents are used to treat severe
disease. Surgical resection of damaged bowel, drainage
of abscesses, or repair of fistula tracts may be necessary.
Ulcerative Colitis
Ulcerative colitis is a nonspecific inflammatory condition
of the colon. The disease is more common in the United
States and Western countries. The disease may arise
at any age, with a peak incidence in the third decade.
7
Unlike Crohn disease, which can affect various sites in
the gastrointestinal tract, ulcerative colitis is confined to
the rectum and colon.
6,7
The disease usually begins in the
rectum and spreads proximally, affecting primarily the
mucosal layer, although it can extend into the submuco-
sal layer. The length of proximal extension varies. It may
involve the rectum alone (ulcerative proctitis), the rec-
tum and sigmoid colon (proctosigmoiditis), or the entire
FIGURE 29-6.
Crohn disease. A longitudinal ulcer of
terminal ileum.The larger rounded areas of edematous
damaged mucosa give a “cobblestone” appearance in the
involved mucosa. A portion of the mucosa in the lower right
is uninvolved. (From Rubin R.The gastrointestinal tract. In:
Rubin R, Strayer DS, eds. Rubin’s Pathology: Clinicopathologic
Foundations of Medicine. 6th ed. Philadelphia, PA: Wolters
Kluwer Health | Lippincott Williams &Wilkins; 2012:654).
