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U N I T 8
Gastrointestinal and Hepatobiliary Function
Irritable bowel disease is characterized by persistent
or recurrent symptoms of abdominal pain, altered bowel
function, and varying complaints of flatulence, bloat-
ing, nausea and anorexia, constipation or diarrhea, and
anxiety or depression. A hallmark of IBS is abdominal
pain that is relieved by defecation and associated with a
change in consistency or frequency of stools. Abdominal
pain usually is intermittent, cramping, and in the lower
abdomen. It does not usually occur at night or inter-
fere with sleep. The condition is believed to result from
dysregulation of intestinal motor and sensory func-
tions modulated by the CNS. Persons with IBS tend to
experience increased motility and abnormal intestinal
contractions in response to psychological and physi-
ologic stresses. Although changes in intestinal activity
are normal responses to stress, these responses appear
to be exaggerated in persons with IBS. Women tend to
be affected more often than men. Menarche often is
associated with onset of the disorder. Women frequently
notice an exacerbation of symptoms during the premen-
strual period, suggesting a hormonal component.
The diagnosis of IBS is usually based on signs and
symptoms of abdominal pain or discomfort, bloating,
and constipation or diarrhea, or alternating bouts of con-
stipation and diarrhea. A commonly used set of diagnos-
tic criteria requires continuous or recurrent symptoms of
at least 12 weeks’ duration (which may be nonconsecu-
tive) of abdominal discomfort or pain in the preceding 12
months, with two of three accompanying features: relief
with defecation, onset associated with a change in bowel
frequency, and associated with a change in form (appear-
ance) of stool. Other symptoms that support the diagno-
sis of IBS include abnormal stool frequency (more than
three times per day or less than three times per week),
abnormal stool form (lumpy/hard or loose/watery),
abnormal stool passage (straining, urgency, or feeling of
incomplete evacuation), passage of mucus, and bloating
or feeling of abdominal distention. A history of lactose
intolerance should be considered because intolerance to
lactose and other sugars may be a precipitating factor in
some persons. The acute onset of symptoms raises the
likelihood of organic disease, as do weight loss, anemia,
fever, occult blood in the stool, nighttime symptoms, or
signs and symptoms of malabsorption. These signs and
symptoms require additional investigation.
The treatment of IBS focuses on methods of stress man-
agement, particularly those related to symptom produc-
tion. Reassurance is important. Usually, no special diet is
indicated, although adequate fiber intake usually is recom-
mended. Avoidance of offending dietary substances such as
fatty and gas-producing foods, alcohol, and caffeine-con-
taining beverages may be beneficial. Various pharmaco-
logic agents, including antispasmodic and anticholinergic
drugs, have been used with varying success in treatment of
the disorder. Alosetron is a serotonin antagonist that has
been approved by the U.S. Food and Drug Administration
(FDA) for treatment of women with severe IBS. The drug
appears to act by reducing intestinal secretion, decreasing
visceral afferent nerve activity (thereby reducing abdomi-
nal pain), and reducing intestinal motility. Because the
drug has serious side effects, including severe constipation
and ischemic colitis, its use is restricted to women with
severe IBS with diarrhea who have not responded to con-
ventional treatment and have been educated about the
relative risks and benefits of the agent.
Inflammatory Bowel Disease
The term
inflammatory bowel disease
(IBD) is used
to designate two related inflammatory intestinal dis-
orders: Crohn disease and ulcerative colitis.
6,7,27–29
Although the two diseases differ sufficiently to be
distinguishable, they have many features in common.
Both diseases produce inflammation of the bowel, both
lack confirming evidence of a proven causative agent,
both have a pattern of familial occurrence, and both
can be accompanied by systemic manifestations. Crohn
disease most commonly affects the distal small intes-
tine and proximal colon but can affect any area of the
gastrointestinal tract from the esophagus to the anus,
whereas ulcerative colitis is confined to the colon and
rectum (Fig. 29-5). In Crohn disease the inflammation
is often transmural, whereas in ulcerative colitis it is
typically confined to the mucosa.
The clinical manifestations of both Crohn disease and
ulcerative colitis are ultimately the result of activation
of inflammatory cells with elaboration of inflammatory
mediators that cause nonspecific tissue damage. Both dis-
eases are characterized by remissions and exacerbations
of diarrhea, fecal urgency, and weight loss. Acute com-
plications, such as intestinal obstruction, may develop
during periods of fulminant disease. The distinguishing
characteristics of Crohn disease and ulcerative colitis are
summarized in Table 29-1.
A number of systemic manifestations have been iden-
tified in persons with Crohn disease and ulcerative coli-
tis. These include axial arthritis affecting the spine and
sacroiliac joints and oligoarticular arthritis affecting the
large joints of the arms and legs; inflammatory condi-
tions of the eye, usually uveitis; skin lesions, especially
erythema nodosum; inflammation of the mucous mem-
brane of the mouth (stomatitis); blood disorders (ane-
mia, hypercoagulability); and inflammation of the bile
A
B
Crohn disease
Ulcerative colitis
FIGURE 29-5.
Distribution patterns of disease with
(A)
skip
lesions in Crohn disease and
(B)
continuous involvement of the
colon, beginning with the rectum, in ulcerative colitis.
