Bowel Obstruction

Digestive Blocked intestine

A blockage stopping food, fluid and gas from passing through the intestine, causing pain, vomiting and distension.

Educational summary only — not medical advice, and no substitute for assessment by a clinician. Diagrams are simplified illustrations.

Something blocks the intestine; contents pile up and balloon the bowel above, while the bowel beyond empties and flattens.

Overview

A bowel obstruction is a blockage that prevents the normal passage of food, fluid and gas through the intestine. It can affect the small or large bowel, be partial or complete, and ranges from something that settles with rest to a surgical emergency.

How the system normally works

The intestine is a long muscular tube that propels its contents along by rhythmic squeezing (peristalsis), absorbing nutrients and water on the way. Smooth, one-way flow depends on the tube staying open along its whole length.

What goes wrong

When something blocks the tube — a band of scar tissue (adhesion), a loop caught in a hernia, a tumour, or twisting of the bowel — contents and gas pile up above the blockage and the bowel stretches. The distended bowel cramps as it tries to push past the obstruction, and fluid is drawn into the gut. If the blood supply to a trapped segment is cut off (strangulation), that part of the bowel can be damaged or die — the most dangerous scenario.

Diagram of three causes of bowel obstruction: an adhesion band, a hernia trapping bowel, and a tumour blocking the bowel. — Common causes: scar-tissue bands (adhesions) from previous surgery, a loop trapped in a hernia, or a tumour growing into the channel.

Symptoms and why they happen

Cramping belly pain in waves — the bowel contracting against the blockage.
A bloated, distended belly — trapped gas and fluid.
Vomiting — backed-up contents; in low blockages it may smell feculent.
Inability to pass gas or stool (in complete obstruction).
Constant, severe pain and fever suggest strangulation — an emergency.

Causes and risk factors

Previous abdominal surgery (adhesions — the commonest cause)
Hernias
Bowel cancer (especially in the large bowel)
Inflammatory bowel disease and prior radiation
Twisting of the bowel (volvulus)

How it's diagnosed

Examination, blood tests, and imaging. An abdominal X-ray may show dilated loops with air-fluid levels; a CT scan is more precise — it pinpoints the level and cause and flags signs of strangulation.

Diagram resembling an abdominal X-ray showing dilated bowel loops with air-fluid levels above a blockage and collapsed bowel beyond. — On an X-ray, obstruction shows as swollen loops with air-fluid levels above the blockage and empty, collapsed bowel beyond it.

Treatment and management

Initial care is “drip and suck”: intravenous fluids, nothing by mouth, and a tube through the nose to drain the stomach and decompress the bowel. Many partial obstructions (especially from adhesions) settle this way. Surgery is needed for complete obstruction, strangulation, or causes like hernias and tumours.

Possible complications

Strangulation with dead bowel, perforation, severe dehydration and electrolyte disturbance, and widespread infection if untreated.

Prevention and outlook

Prevention is limited but includes timely repair of hernias and bowel-cancer screening. Outlook depends on the cause and on whether the blood supply is compromised; uncomplicated cases generally do well.

When to seek emergency care

Constant severe pain, fever, or a tense rigid belly — possible strangulation; urgent surgical assessment.
Persistent vomiting with a swollen belly and no passage of gas or stool.