Last updated: 02/17/2009

The small intestine is composed of three major sections: the duodenum just below the stomach; the jejunum, or middle portion; and the ileum, which empties into the large intestine. The large intestine is composed of the colon, where stool is formed;...

and the rectum, which empties to the outside of the body through the anal canal. A blockage that occurs in the small intestine is called a small bowel obstruction, and one that occurs in the colon is a colonic obstruction.

There are numerous conditions that may lead to an intestinal obstruction. The three most common causes of small bowel obstruction are adhesions, which are bands of scar tissue that form in the abdomen following injury or surgery; hernias, which develop when a portion of the intestine protrudes through a weak spot in the abdominal wall; and cancerous tumors. Adhesions account for approximately 50% of all small bowel obstructions, hernias for 15%, and tumors for 15%. Other causes include volvulus, or formation of kinks or knots in the bowel; the presence of foreign bodies in the digestive tract; intussusception, which occurs when a portion of the intestine telescopes or pulls over another portion; infection; and congenital defects. While most small bowel blockages can be treated with the administration of intravenous (IV) fluids and decompression of the bowel by the insertion of a nasogastric (NG) tube, surgical intervention is necessary in approximately 25% of patients with a partial obstruction, and 50%–65% of patients with a complete obstruction.

An obstruction of the large intestine is less common than blockages of the small intestine. Blockages of the large bowel are usually caused by colon cancer; volvulus; diverticulitis (inflammation of sac-like structures called diverticula that form in the intestines); ischemic colitis (inflammation of the colon resulting from insufficient blood flow); Crohn's disease (a disease that causes chronic inflammation of the intestines); inflammation due to radiation therapy; and the presence of foreign bodies. As in the case of small bowel obstruction, most patients with a blockage of the large intestine can be treated with IV fluids and bowel decompression.