Small bowel obstruction

What is small bowel obstruction?

Small bowel obstruction is a blockage of the small intestine that stops food, fluid and gas from moving through. Fluid and gas build up above it, so the abdomen swells and vomiting starts. A blockage can be partial or complete, and it needs hospital care because the trapped bowel can lose its blood supply.

The small intestine carries digested food from the stomach to the large bowel. In a partial blockage, some contents still get through. Without treatment the blocked bowel can lose its blood supply and the tissue can die, which is why a suspected obstruction is assessed in hospital rather than at home.

What causes small bowel obstruction?

Scar tissue called adhesions, usually left by earlier abdominal surgery, is the most common cause of small bowel obstruction. Other causes are hernias that trap a loop of bowel, Crohn's disease that narrows or twists the intestine, tumours, and intussusception, where one part of the bowel slides into the next.

• Adhesions, bands of scar tissue that usually follow earlier abdominal or pelvic surgery
• A hernia that traps a loop of bowel, for example in the groin or near the belly button
• Crohn's disease, which can narrow or twist the intestine
• Tumours that press on or grow into the bowel
• Intussusception, where one part of the intestine slides into the next like a telescope
• A swallowed object, which is uncommon in adults

What are the symptoms?

Small bowel obstruction usually causes crampy abdominal pain that comes in waves, a swollen and bloated abdomen, nausea and vomiting, and being unable to pass wind. Some people become constipated, while others have diarrhoea at first as the bowel below the blockage empties.

• Crampy pain in the abdomen that comes in waves
• Swelling and bloating of the abdomen
• Nausea and vomiting
• Being unable to pass wind
• Constipation, or sometimes diarrhoea as the bowel below empties

When is small bowel obstruction an emergency?

Suspected small bowel obstruction needs same-day hospital assessment. Go to an emergency department for crampy pain with vomiting and no wind passing, constant severe pain, fever, a fast heart rate, or a hernia lump that is painful, firm and will not go back in, as these can mean the bowel is at risk.

The warning signs below need prompt attention.

• Constant, severe abdominal pain rather than pain that comes and goes
• Fever or a fast heart rate
• Repeated vomiting with no wind or stool passed
• A hernia lump that is painful, firm and will not go back in
• Feeling faint, confused or very unwell

How is it diagnosed?

Small bowel obstruction is diagnosed from your symptoms, any history of abdominal operations, and an examination of the abdomen. Blood tests check hydration and infection. An X-ray can show the blockage, and a CT scan is the usual test to locate it, find the cause and check for signs that the bowel is in danger.

• Questions about your symptoms and any past abdominal operations
• Examination of the abdomen for swelling, tenderness or a hernia
• Blood tests to check hydration, salts and signs of infection
• Abdominal X-ray
• CT scan to find where the blockage is, what is causing it and whether the bowel is at risk

How is small bowel obstruction treated?

Treatment starts in hospital with nothing by mouth, fluids through a drip and a tube through the nose to drain the stomach. Many adhesive blockages settle this way. Surgery is needed if the blockage does not clear or the bowel may be losing its blood supply, sometimes by keyhole surgery.

• Admission to hospital with nothing to eat or drink so the bowel can rest
• Fluids and salts through a drip
• A nasogastric tube through the nose into the stomach to drain fluid and gas
• Careful monitoring, as many blockages caused by adhesions settle without an operation
• Surgery when the blockage does not clear, or straight away if the bowel may be losing its blood supply
• Keyhole (laparoscopic) surgery for selected simple adhesive blockages, or open surgery when needed
• Removal of a damaged section of bowel, sometimes with a temporary stoma

What are the risks and complications?

The main danger of small bowel obstruction is loss of blood supply to the trapped bowel, which can cause tissue death, perforation and infection. Vomiting can cause dehydration and salt imbalance. Blockages can recur because adhesions can form again, and surgery carries its own risks.

• Loss of blood supply to the trapped bowel, which can lead to tissue death
• A hole (perforation) in the bowel and infection inside the abdomen
• Dehydration and salt imbalance from vomiting
• The blockage coming back, since new adhesions can form after any abdominal operation
• General risks of surgery and anaesthesia if an operation is needed