Bowel obstruction

Either the large or small bowel may become obstructed, leading to symptoms of colicky abdominal pain, distension, vomiting and constipation.

Obstruction may be due to causes within the bowel lumen, within the wall of the bowel, or external to the bowel (such as compression, entrapment or volvulus).

Bowel obstruction may be complicated by dehydration and electrolyte abnormalities due to vomiting; respiratory compromise from pressure on the diaphragm by a distended abdomen, or aspiration of vomitus; bowel ischaemia or perforation from prolonged distension or pressure from a foreign body.

Some causes of bowel obstruction may resolve spontaneously; many require operative treatment.

Causes of small bowel obstruction include:

• Adhesions from previous abdominal surgery
• Hernias containing bowel
• Neoplasms, benign or malignant
• Inflammatory bowel disease causing adhesions or inflammatory strictures
• Intususseption in children
• Volvulus
• Ischaemic strictures
• Foreign bodies

Causes of large bowel obstruction include:

• Neoplasmss
• Hernias
• Inflammatory bowel disease
• Sigmoid or caecal volvulus
• Faecal impaction

In small bowel obstruction the pain tends to be colicky (cramping and intermittent) in nature, with spasms lasting a few minutes. The pain tends to be central and mid-abdominal. Vomiting occurs before constipation.

In large bowel obstruction the pain is felt lower in the abdomen and the spasms last longer. Constipation occurs earlier and vomiting may be less prominent.

Proximal obstruction of the large bowel may present as small bowel obstruction.

Radiological signs of bowel obstruction include bowel distension and the presence of multiple (more than six) gas-fluid levels on supine and erect abdominal radiographs.

Contrast enema or small bowel series or CT scan can be used to define the level of obstruction, whether the obstruction is partial or complete, and to help define the cause of the obstruction. Colonoscopy, small bowel investigation with ingested camera or push endoscopy, and laparoscopy are other diagnostic options.

Treatment involves insertion of a nasogastric tube (particularly for small bowel obstruction), correction of dehydration and electrolyte abnormalities, and treating the cause of the obstruction. Adhesive obstructions often settle without surgery, but if prolonged may require surgical intervention.

Differential diagnoses of bowel obstruction include

• Ileus
• Pseudo-obstruction, or Ogilvie's syndrome
• Intra-abdominal sepsis
• Pneumonia or other systemic illness.