Bowel Obstruction

How bowel obstruction happens

Normally, waves of muscle contraction push contents through about 20 feet (6 m) of small intestine and 5 feet (1.5 m) of large intestine. When the bowel is blocked, fluid and gas build up above the blockage. The bowel stretches, causing cramping pain and swelling. Fluid is lost into the bowel and by vomiting, leading to dehydration and salt imbalances. If the bowel is twisted or squeezed, its blood supply can be cut off (strangulation), causing tissue death and perforation within hours.

Mechanical obstruction vs ileus

• Mechanical obstruction: a physical blockage.
• Ileus (functional obstruction): the bowel stops moving without a blockage, after surgery, with infection, low potassium or some medicines such as opioids. Ogilvie syndrome is a similar condition of the colon.

Causes

Small bowel obstruction (most common)

• Adhesions: bands of scar tissue after abdominal or pelvic surgery cause most small bowel obstructions in adults. They can occur years after an operation. See adhesive small bowel obstruction.
• Hernias: bowel trapped in an inguinal, femoral, umbilical or incisional hernia.
• Crohn's disease: inflamed or scarred narrowings.
• Tumors, including cancer that has spread.
• Gallstone ileus, bezoars and swallowed objects (rare).
• Intussusception: one part of the bowel telescopes into the next; most common in young children.

Large bowel obstruction

• Colorectal cancer: the most common cause in adults.
• Volvulus: twisting of the colon, usually the sigmoid colon in older adults.
• Diverticular disease causing a stricture.
• Fecal impaction: hard stool blocking the rectum, especially in older or immobile people.

In babies and children

Intussusception, malrotation with volvulus, Hirschsprung disease, pyloric stenosis and intestinal atresia.

Symptoms

Constant, severe pain, fever and tenderness suggest strangulation or perforation.

Diagnosis

• History and examination: past surgery, hernias, bowel habit changes; checking for distension, tenderness, hernias and bowel sounds.
• Blood tests: electrolytes, kidney function, blood count and lactate (raised when the bowel is short of blood).
• CT scan of the abdomen: the key test. It shows the site and cause of the blockage and signs of strangulation.
• X-ray: can show dilated loops and fluid levels, but CT is more accurate.

Treatment

Initial hospital treatment ("drip and suck")

• nothing by mouth
• IV fluids and correction of electrolytes
• a nasogastric tube through the nose into the stomach to remove fluid and gas and relieve vomiting
• pain relief and anti-nausea medicine
• monitoring urine output

Many adhesive small bowel obstructions settle within 1 to 3 days with this treatment. A drink of water-soluble contrast (such as Gastrografin) helps predict which will settle and may speed resolution.

Surgery

Needed for strangulation, perforation, a trapped hernia, most large bowel obstructions from cancer, and obstructions that do not resolve. Surgery may involve cutting adhesions, repairing a hernia, removing damaged or cancerous bowel, and sometimes a temporary stoma.

Other procedures

• Colonic stents placed through a scope can relieve obstruction from colon cancer, either as a bridge to surgery or as palliative treatment.
• Sigmoid volvulus can often be untwisted with a flexible scope, with surgery later to prevent recurrence.
• Intussusception in children is usually reduced with an air or contrast enema.

Complications

• dehydration and kidney injury
• strangulation and bowel death
• perforation and peritonitis
• sepsis
• aspiration of vomit into the lungs
• recurrence, especially with adhesions

Outlook

With prompt treatment, most people recover well. Adhesive obstructions can recur. Outcomes after obstruction from cancer depend on the stage of the cancer.

Frequently asked questions

What are the first signs of a bowel obstruction?

Early signs include cramping belly pain that comes in waves, bloating, loss of appetite, nausea and vomiting, and reduced or no passing of stool or gas. Symptoms usually worsen over hours to days. Seek emergency care if these occur together.

What causes a bowel obstruction?

In adults the most common causes are scar tissue (adhesions) from previous surgery, hernias and colon cancer. Others include twisting of the bowel (volvulus), Crohn's disease strictures, impacted stool and, in children, intussusception.

Can a bowel obstruction clear on its own?

Partial or adhesive small bowel obstructions often clear within a few days with hospital treatment: no food, IV fluids and a tube to drain the stomach. Complete obstructions, strangulation and most large bowel obstructions need surgery or a procedure.

Can you still poop with a bowel obstruction?

Sometimes, at first. Stool and gas below the blockage may pass early on, and partial obstructions allow some passage. Being unable to pass any gas or stool with pain, swelling and vomiting suggests a complete obstruction and needs emergency care.

How is a bowel obstruction diagnosed?

A CT scan of the abdomen is the main test. It shows where the blockage is, what is causing it, and whether the blood supply to the bowel is at risk. Blood tests check for dehydration, salt imbalances and signs of bowel damage.