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Intestinal obstruction is a blockage of your small intestine or colon that prevents food and fluid from passing through. Intestinal obstruction can be caused by many conditions, but it's most often the result of fibrous bands of tissue in the intestine (adhesions), hernias or tumors.

Not only can intestinal obstruction result in an array of uncomfortable signs and symptoms — including crampy abdominal pain and swelling of your abdomen, nausea and vomiting — if left untreated, intestinal obstruction can cause the blocked parts of your intestine to die. This tissue death can lead to perforation of the intestine, severe infection and shock.

Because of the serious complications that can develop from intestinal obstruction, seek emergency medical attention if you develop signs or symptoms of intestinal obstruction. With prompt medical care, intestinal obstruction can often be successfully treated.

Signs and symptoms of intestinal obstruction include:

• Crampy abdominal pain that comes and goes (intermittent)
• Nausea
• Vomiting
• Inability to have a bowel movement or pass gas
• Swelling of the abdomen (distention)
• Abdominal tenderness

Many conditions can cause intestinal obstruction. The causes often differ, however, depending on whether the obstruction occurs in the small intestine or in the colon. When intestinal obstruction is referred to as "mechanical," it means something is physically blocking the intestine. Blockage of the intestine can be partial or complete. Signs and symptoms of paralytic ileus — a condition in which the intestines don't function properly — may be similar, but no physical obstruction is present.

Mechanical obstruction of the small intestine
Common causes of mechanical obstruction in the small intestine include the following:

• Intestinal adhesions. These bands of fibrous tissue in the intestines may be present at birth (congenital). But, more often, they form after abdominal surgery. Intestinal adhesions can bind sections of your intestine, blocking the passage of food and fluids.
• Hernias. Hernias occur when part of your intestine protrudes into another part of your body. If a loop of intestine becomes trapped due to a hernia, it will cause intestinal obstruction.
• Tumors. A tumor within your small intestine may block the passage of food and fluids, causing obstruction.

Adhesions, hernias and tumors account for about 90 percent of cases of mechanical small intestine obstruction. Other causes include:

• Telescoping of a portion of the intestine into another portion (intussusception)
• Twisting of the intestine (volvulus)
• Narrowing of the outlet from the stomach (stricture)

Mechanical obstruction of the colon
Mechanical intestinal obstruction in the colon is less common than in the small intestine. Only 10 percent to 15 percent of mechanical obstruction occurs in the colon. Adhesions and hernias rarely cause obstruction in the colon. The most common causes of colonic obstruction include the following:

• Cancer
• Diverticulitis — a condition in which small, bulging pouches (diverticula) in the digestive tract become inflamed or infected
• Twisting of the colon (volvulus)

Less common causes of intestinal obstruction in the colon include:

• Telescoping of a portion of the colon into another portion (intussusception)
• Impacted feces
• Narrowing of the colon (stricture)
• Foreign bodies (swallowed objects that block the colon)
  

Paralytic ileus
Paralytic ileus, or pseudo-obstruction, can cause signs and symptoms of intestinal obstruction. In paralytic ileus, although there is no blockage, the intestines don't function properly; movement of the intestines is greatly reduced or absent. The intestines are unable to move food and fluid smoothly through the digestive system.

Paralytic ileus can affect any part of the intestine. The most common cause of paralytic ileus is abdominal surgery. Right after abdominal surgery, the intestines don't function normally. A nasogastric (NG) tube and intravenous fluids are often necessary until the intestines begin to function again. Postoperative paralytic ileus is not a form of mechanical obstruction.

You're at an increased risk of developing intestinal obstruction if you've had abdominal surgery of any kind, surgery to remove part of your intestine (bowel resection) or other pelvic surgery, previous surgery for obstruction, or if you've had your appendix surgically removed (appendectomy). These surgeries can cause adhesions, which are one of the most common causes of intestinal obstruction.

Other conditions that increase your risk of intestinal obstruction include:

• Crohn's disease — an inflammatory condition that can cause the intestine's walls to thicken, narrowing its passageway
• Cancer within your abdomen, especially if you had surgery to remove an abdominal tumor
• A history of constipation
• Malrotation, a condition present at birth (congenital) in which the intestine doesn't develop correctly

Intestinal obstruction requires prompt medical care. If you develop the following signs or symptoms, seek medical help right away:

• Crampy abdominal pain that comes and goes (intermittent)
• Nausea
• Vomiting
• Inability to have a bowel movement or pass gas (constipation), associated with crampy abdominal pain
• Swelling of the abdomen (distention)
• Abdominal tenderness

You doctor will ask about your medical history and your symptoms. He or she will also do a physical exam to assess your situation. The doctor may suspect intestinal obstruction if your abdomen is swollen or tender, or if there's a lump in your abdomen.

To confirm a diagnosis of intestinal obstruction, your doctor may recommend abdominal X-ray, ultrasound or computerized tomography (CT) scans. These tests also help your doctor determine if the obstruction is paralytic ileus or if it's a mechanical obstruction, and if it's a partial or a complete obstruction.

If left untreated, intestinal obstruction can cause serious complications. As the intestine becomes congested, its ability to absorb food and fluids decreases. Decreased absorption may cause vomiting, dehydration and, eventually, can result in kidney failure, which may cause you to go into shock.

Intestinal obstruction can also cut off the blood supply to the affected portion of your intestine. If left untreated, lack of blood causes the intestinal wall to die. Tissue death can result in a tear (perforation) in the intestinal wall, which can lead to peritonitis, an infection of the lining of your abdominal cavity.

Peritonitis is a life-threatening condition that requires immediate medical and surgical attention. Signs and symptoms of peritonitis include:

• Abdominal pain or tenderness
• Abdominal swelling
• Nausea
• Vomiting
• Fever
• Thirst
• Low urine output
• Fluid in the abdomen
• Inability to have a bowel movement or pass gas

Peritonitis may cause you to go into shock. Signs and symptoms of shock include:

• Cool, clammy skin that may be pale or gray
• A weak and rapid pulse
• Abnormal breathing that may be either slow and shallow or very rapid
• Dilated pupils in the eyes
• Lackluster eyes that seem to stare

A person who is in shock may be conscious or unconscious. Shock is an emergency condition that requires immediate medical care.

Treatment for intestinal obstruction requires hospitalization. When you arrive at the hospital, the doctors will first stabilize your medical condition. This includes giving you fluids through an intravenous (IV) line, putting a nasogastric (NG) tube through your nose and into your stomach to allow the intestines to decompress, and placing a thin, flexible tube (catheter) into your bladder to drain urine.

Specific treatment depends on the cause of your condition. If your doctor determines that your signs and symptoms are caused by paralytic ileus, he or she may monitor your condition for a day or two in the hospital. Paralytic ileus is often a temporary condition that gets better on its own. If paralytic ileus doesn't improve within several days, your doctor may prescribe medication that causes muscle contractions, which can help move food and fluids through your intestines.

If you have mechanical obstruction in which some food and fluid can still get through (partial obstruction), decompressing your intestine with an NG tube may improve the condition, and no further treatment is necessary. If the obstruction does not clear within a day or so, you may need surgery to relieve the obstruction.

Complete obstruction, in which nothing can pass through your intestine, is a medical emergency that requires immediate surgery to relieve the blockage.

Prevention of intestinal obstruction depends on the cause. Some causes, such as intussusception and volvulus, may not be preventable. However, treatment of conditions related to intestinal obstruction, such as hernias and tumors, may reduce your risk of developing obstruction.