Cancer Health Center

There are four types of obstruction:

1. Simple.
2. Closed-loop.
3. Strangulated.
4. Incarcerated.

A simple obstruction is blocked in one place; a closed-loop obstruction is blocked in two places. A closed-loop obstruction may develop when the bowel twists around on itself, isolating the looped section of the bowel and obstructing the portion above it. With a strangulated obstruction, there is decreased blood flow to the bowel that, if not relieved, will develop into an incarcerated obstruction, and the bowel will become necrotic.

The obstructing mechanism can be mechanical or nonmechanical. Mechanical factors can be anything that causes a narrowing of the intestinal lumen (e.g., inflammation or trauma to the bowel, neoplasms, adhesions, hernias, volvulus, or a compression from outside the intestinal tract).[1] Nonmechanical factors include those that interfere with the muscle action or innervation of the bowel: paralytic ileus, mesenteric embolus or thrombus, and hypokalemia.

Eighty percent of bowel obstructions occur in the small intestine; the other 20% occur in the colon.[2] Bowel obstructions are frequently seen in the ileum. Small bowel obstructions are caused often by adhesions or hernias, whereas large bowel obstructions are caused by carcinomas, volvulus, or diverticulitis. The presentation of obstruction will relate to whether the small or large intestine is involved.

Etiology of Bowel Obstruction

The most common malignancies that cause bowel obstruction are cancers of the colon, stomach, and ovary. Extra-abdominal cancers (such as lung and breast cancers and melanoma) can spread to the abdomen, causing bowel obstruction.[3] Patients who have had abdominal surgery or abdominal radiation are also at higher risk of developing bowel obstruction.[2] Bowel obstructions are most common during advanced stages of disease.

Assessment and Diagnosis of Bowel Obstruction

Examination of the patient will determine the presence or absence of abdominal pain, vomiting, and evidence of the passage of flatus or stool. A complete blood cell count, electrolyte panel, and urinalysis are obtained to evaluate fluid and electrolyte imbalance and/or sepsis. An elevated white blood cell count (15,000-20,000/mm³) suggests bowel necrosis. Flat and upright abdominal films as well as a barium enema may be necessary to determine where the obstruction is located. While it remains controversial, an upper gastrointestinal series is contraindicated with an acutely presenting obstruction because it can cause a partial obstruction to become complete or may further complicate a total obstruction. If the patient is exhibiting dehydration, oliguria, or shock, perforation of the bowel may have occurred, and immediate medical or surgical intervention is indicated. (Refer to the Nausea, Vomiting, Constipation, and Bowel Obstruction in Advanced Cancer section in the PDQ summary on Nausea and Vomiting for more information.)

Treatment of Acute Bowel Obstruction

Careful serial examinations are necessary in the management of patients with progressive abdominal symptoms that may be due to acute bowel obstruction. The principles of supportive care in this setting include volume resuscitation, correction of electrolyte imbalances, and transfusion support (if necessary). These measures should precede or accompany decompression efforts.