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An obstruction
of the intestine is a blockage that completely stops or seriously
impairs the passage of intestinal contents.
An obstruction may occur
anywhere along the small or large intestine. The part of the intestine
above the obstruction continues to function. The intestine enlarges
as it fills with food, fluid, digestive secretions, and gas. The intestinal
lining becomes swollen and inflamed. If the condition is not treated,
the intestine can rupture, leaking its contents and causing inflammation
and infection of the abdominal cavity.
In newborns and infants,
intestinal obstruction is commonly caused by a birth defect, a hard
mass of intestinal contents (meconium), or a twisting of a loop
of intestine (volvulus).
In adults, an
obstruction of the first segment of the small intestine (duodenum)
may be caused by cancer of the pancreas; scarring from an ulcer,
a previous operation, or Crohn's disease; or adhesions, in which
a fibrous band of connective tissue traps the intestine. An obstruction
also can occur when part of the intestine bulges through an abnormal
opening (hernia), such as a weakness in the muscles of the abdomen,
and becomes trapped. Rarely, a gallstone, a mass of undigested food,
or a collection of parasitic worms may block the intestine.
An obstruction of the
large intestine is commonly caused by cancer. Obstruction also tends
to occur (as a result of scarring and connective bands of scar tissue
[adhesions]) in people who have previously undergone abdominal surgery.
A hard lump of stool (fecal impaction) also may cause a blockage.
If an obstruction
cuts off the blood supply to the intestine, the condition is called
strangulation. Strangulation occurs in nearly 25% of people with
small-intestinal obstruction. Usually, strangulation results from
the trapping of part of the intestine in an abnormal opening (strangulated
hernia); the twisting of a loop of intestine (volvulus); or the telescoping
of a loop of intestine into another loop (intussusception). Gangrene
can develop in as few as 6 hours. With gangrene, the intestinal
wall dies, usually causing rupture, which leads to inflammation
of the lining of the abdominal cavity (peritonitis) and infection.
Without treatment, the person may die.
Symptoms and
Diagnosis
Intestinal obstruction
usually causes cramping pain
in the abdomen, accompanied by bloating and disinterest in eating
(anorexia). The pain may become severe and steady. Vomiting, which
is common, begins later with large-intestinal obstruction than it
does with small-intestinal obstruction. Complete obstruction causes
severe constipation, while partial obstruction may cause diarrhea.
A fever is common and is particularly likely if the intestinal wall
ruptures. Rupture can rapidly lead to severe inflammation and infection, causing
shock (see Shock).
A doctor examines the
abdomen for tenderness, swelling, or masses. When an obstruction
occurs, the sounds normally made by a functioning intestine (bowel
sounds), which can be heard through a stethoscope, may be much louder
and higher pitched, or they may be absent. If rupture has caused
peritonitis, the person will feel pain when the doctor presses on
the abdomen; often the pain increases when the doctor suddenly releases
the pressure (rebound tenderness).
X-rays may show dilated
loops of intestine that indicate the location of the obstruction. The
x-rays also may reveal air around the intestine or under the layer
of muscle that separates the abdomen and the chest (diaphragm). Air
normally is not found in those places and thus is a sign of rupture.
Treatment
Anyone suspected of having
an intestinal obstruction is hospitalized. Usually, a long, thin
tube is passed through the nose and placed in the stomach or intestine.
Suction is applied to the tube to remove the material that has accumulated
above the blockage. Fluid and electrolytes (sodium, chloride, and
potassium) are given intravenously to replace water and salts lost
from vomiting or diarrhea.
Sometimes an obstruction
resolves without further treatment, especially if caused by scarring
or bands of connective tissue (adhesions). Occasionally, an endoscope
(a flexible viewing tube), which is advanced through the anus, or a
barium enema, which inflates the large intestine, may be used to
treat some disorders, such as a twisted intestinal segment in the lower
part of the large intestine. Most often, however, surgery is performed
as soon as possible. The cause of the obstruction determines whether
the surgeon can relieve the blockage without removing a segment
of the intestines. Sometimes fibrous bands can be released, although
they tend to recur.
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