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Intestinal Obstruction

by Parswa Ansari, MD

An obstruction of the intestine is a blockage that completely stops or seriously impairs the passage of intestinal contents.

  • The most common cause in adults is scar tissue resulting from previous abdominal surgery, hernias, and tumors.

  • Pain, fever, bloating, and a lack of interest in eating are common.

  • The diagnosis is based on the results of a physical examination and x-rays.

  • Surgery to remove the obstruction is often needed.

An obstruction may occur anywhere along the small or large intestine and can be partial or complete. The part of the intestine above the obstruction continues to function. This part of 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 (peritonitis).

Causes

In newborns and infants, intestinal obstruction is commonly caused by a birth defect, a hard mass of intestinal contents (meconium), a twisting of a loop of intestine (volvulus), intestinal atresia, or a telescoping of one segment of intestine into another (intussusception).

In adults, the most common causes overall are bands of internal scar tissue resulting from previous abdominal surgery (adhesions), parts of the intestine bulging through an abnormal opening (hernias), and tumors. The likelihood of a particular cause varies depending on the part of the intestine affected.

An obstruction of the first segment of the small intestine (duodenum) may be caused by cancer of the pancreas, scarring from an ulcer, or Crohn disease. Rarely, a gallstone, a mass of undigested food, or a collection of parasitic worms may block other parts of the small intestine.

An obstruction of the large intestine is commonly caused by cancer, diverticulitis, or a hard lump of stool (fecal impaction). Adhesions and volvulus are less common causes of large-intestinal obstruction.

Strangulation

If an obstruction cuts off the blood supply to the intestine, the condition is called strangulation. Strangulation occurs in nearly 10 to 20% of people with small-intestinal obstruction. Usually, strangulation results when part of the intestine becomes trapped in an abnormal opening (strangulated hernia), volvulus, or intussusception. Gangrene can develop in as few as 6 hours. With gangrene, the intestinal wall dies, usually causing rupture, which leads to peritonitis, shock, and, if untreated, death.

What Causes Intestinal Strangulation?

Intestinal strangulation (cutting off of the blood supply to the intestine) usually results from one of three causes.

Symptoms and Diagnosis

Intestinal obstruction usually causes cramping pain in the abdomen, accompanied by bloating and disinterest in eating (anorexia). Vomiting is common with small-intestinal obstruction but is less common and begins later with large-intestinal obstruction. Complete obstruction causes severe constipation, whereas partial obstruction may cause diarrhea. With strangulation, pain may become severe and steady. A fever is common and is particularly likely if the intestinal wall ruptures.

A doctor examines the abdomen for tenderness, swelling, or masses. When an obstruction occurs, the abdomen is almost always swollen. 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. The abdomen is usually not very tender when the doctor presses on it unless rupture has caused peritonitis.

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 or a dead bowel.

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 by vein (intravenously) to replace water and salts lost from vomiting or diarrhea.

Sometimes an obstruction resolves without further treatment, especially if caused by scarring or adhesions. Occasionally, an endoscope (a flexible viewing tube), which is inserted 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 done as soon as possible if doctors are concerned about strangulation. The cause of the obstruction and the appearance of the intestine determine whether the surgeon can relieve the blockage without removing a segment of the intestine. Sometimes adhesions can be cut to release the trapped segment of intestine, although they tend to recur. In some cases, a colostomy (see Figure: Understanding Colostomy) is required.

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