Obstruction of the Intestine
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.
 See the figure What Causes Intestinal Strangulation?
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 Section 3, Chapter 24).
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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