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U N I T 8
Gastrointestinal and Hepatobiliary Function
Secretory diarrhea
occurs when the secretory processes
of the bowel are increased. Secretory diarrhea also occurs
when excess bile acids remain in the intestinal contents as
they enter the colon. This often occurs with disease pro-
cesses of the ileum because bile salts are absorbed there.
It also may occur with bacterial overgrowth in the small
bowel, which interferes with bile absorption.
Inflammatory diarrhea
commonly is associated with
acute or chronic inflammation or intrinsic disease of
the colon, such as ulcerative colitis or Crohn disease.
Inflammatory diarrhea usually is evidenced by frequency
and urgency and colicky abdominal pain. It commonly
is accompanied by tenesmus (i.e., ineffectual and painful
straining at stool), fecal soiling of clothing, and awaken-
ing during the night with the urge to defecate.
Chronic parasitic infections may cause chronic diar-
rhea through a number of mechanisms. Pathogens most
commonly associated with chronic diarrhea include
the protozoans
Entamoeba histolytica, Giardia,
and
Cyclospora.
Immunocompromised individuals are
particularly susceptible to infectious organisms such
as
Cryptosporidia,
cytomegalovirus (CMV), and
Mycobacterium avium-intracellulare
complex that can
cause both acute and chronic diarrhea (see Chapter 16).
Diagnosis andTreatment.
The diagnosis of diarrhea is
based on complaints of frequent stools and a history of
accompanying factors such as concurrent illnesses, med-
ication use, and exposure to potential intestinal patho-
gens. Disorders such as Crohn disease and ulcerative
colitis should be considered. If the onset of diarrhea is
related to travel outside the United States, the possibility
of traveler’s diarrhea must be considered.
Although most acute forms of diarrhea are self-limited
and require no treatment, diarrhea can be particularly
serious in infants and small children, persons with other
illnesses, and the elderly. Thus, the replacement of fluids
and electrolytes is considered to be a primary therapeutic
goal in the treatment of diarrhea. Oral replacement ther-
apy (ORT) can be used in situations of uncomplicated
diarrhea that can be treated at home. First applied to the
treatment of diarrhea in developing countries, ORT can
be regarded as a case of reverse technology, in which the
protocols originally implemented in these countries have
changed health care practices in industrialized countries
as well.
42
Complete ORT solutions contain carbohydrate,
sodium, potassium, chloride, and base to replace that lost
in the diarrheal stool.
42,46
Commonly used beverages such
as apple juice and cola drinks, which have increased osmo-
larity because of their high carbohydrate and low electro-
lyte content, are not recommended. The effectiveness of
ORT is based on the coupled transport of sodium and
glucose or other actively transported small organic mol-
ecules. ORT can be particularly effective in treating dehy-
dration associated with diarrheal diseases in infants and
small children. Children who are severely dehydrated with
changes in vital signs or mental status require emergency
intravenous fluid resuscitation. After initial treatment with
intravenous fluids, these children can be given ORT.
Evidence suggests that feeding should be continued
during diarrheal illness, particularly in children.
46
Starch
and simple proteins are thought to provide co-transport
molecules with little osmotic activity, increasing fluid
and electrolyte uptake by intestinal cells. The luminal
contents associated with early refeeding are also known
to contain growth factor for enterocytes and help facili-
tate repair after injury. It is recommended that children
who require rehydration therapy because of diarrhea
be fed an age-appropriate diet. Although there is little
agreement on which foods are best, fatty foods and
foods high in simple sugars are best avoided. Almost
all infants with acute gastroenteritis can tolerate breast-
feeding. For formula-fed infants, diluted formula does
not provide an advantage over full-strength formula.
Drugs used in the treatment of diarrhea include
diphenoxylate (Lomotil) and loperamide (Imodium),
which are opium-like drugs. These drugs decrease gas-
trointestinal motility and stimulate water and electro-
lyte absorption. Adsorbents, such as kaolin and pectin,
adsorb irritants and toxins in the bowel. These ingredi-
ents are included in many over-the-counter antidiarrheal
preparations because they adsorb toxins responsible for
certain types of diarrhea. Antidiarrheal medications
should not be used in persons with bloody diarrhea, high
fever, or signs of toxicity because of the risk of worsen-
ing the disease. Antibiotics should be reserved for use in
persons with identified enteric pathogens.
Constipation
Constipation can be defined as the infrequent or difficult
passage of stools.
47–49
The difficulty with this definition
arises from the many individual variations of function
that are normal. What is considered normal for one
person (e.g., two or three bowel movements per week)
may be considered evidence of constipation by another.
CHART 29-1
Chronic Diarrhea
Hyperosmotic diarrhea
Saline cathartics
Lactase deficiency
Secretory diarrhea
Acute infectious diarrhea
Failure to absorb bile salts
Fat malabsorption
Chronic laxative abuse
Carcinoid syndrome
Zollinger-Ellison syndrome
Fecal impaction
Inflammatory bowel disease
Crohn disease
Ulcerative colitis
Infectious disease
Shigellosis
Salmonellosis
Irritable bowel syndrome
