From Ask Dr Wiki
Bowel obstruction is a mechanical or functional obstruction of the intestines, preventing the normal transit of the products of digestion. It can occur at any level distal to the duodenum of the small intestine and is a medical emergency. Although many cases are not treated surgically, it is a surgical problem.
Small bowel obstruction
Causes of small bowel obstruction include:
- Adhesions from previous abdominal surgery
- Hernias containing bowel
- Crohn's disease causing adhesions or inflammatory strictures
- Neoplasms, benign or malignant
- Intussusception in children
- Ischaemic strictures
- Foreign bodies (e.g. gallstones in gallstone ileus, swallowed objects)
- Intestinal atresia
- Carcinoid rare, preferred location: ileum
Large bowel obstruction
Causes of large bowel obstruction include:
- Inflammatory bowel disease
- Colonic volvulus (sigmoid, caecal, transverse colon)
- Faecal impaction
- Colon atresia
- Benign strictures (Diverticular Disease)
Differential diagnoses of bowel obstruction include:
- Pseudo-obstruction or Ogilvie's syndrome
- Intra-abdominal sepsis
- Pneumonia or other systemic illness.
Signs, symptoms and causes
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.
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.
According to a meta-analysis of prospective studies by the Cochrane Collaboration, the appearance of water-soluble contrast in the cecum on an abdominal radiograph within 24 hours of oral administration predicts resolution of an adhesive small bowel obstruction with a pooled sensitivity of 96% and specificity of 96%. PMID 15674958
Some causes of bowel obstruction may resolve spontaneously; many require operative treatment.
In adults, frequently the surgical intervention and the treatment of the causative lesion are required. In malignant large bowel obstruction, endoscopically placed self-expanding metal stents may be used to temporarily relieve the obstruction as a bridge to surgery, or as palliation.
Small bowel obstruction
In the management of small bowel obstructions it is often said that "[n]ever let the sun rise or set on small-bowel obstruction" because they are sometimes fatal if treatment is delayed.
Treatment for a small bowel obstruction is both non-surgical (conservative) and surgical.
Conservative treatment involves insertion of a nasogastric tube, correction of dehydration and electrolyte abnormalities. Opioid pain relievers may be used for patients with severe pain. Antiemetics may be administered if the patient is vomiting. Adhesive obstructions often settle without surgery. If obstruction is complete a surgery is required.
Small bowel obstruction caused by Crohn's disease, peritoneal carcinomatosis, sclerosing peritonitis, radiation enteritis and postpartum bowel obstruction are typically treated conservatively, i.e. without surgery. Conversely, a small bowel obstruction in a "virgin abdomen" (an abdomen that has not seen an operation) is almost never treated conservatively.
Bowel obstruction in children
Fetal and neonatal bowel obstructions are often caused by an intestinal atresia where there is a narrowing or absence of a part of the intestine. These atresias are often discovered before birth via a sonogram and treated with using laparotomy after birth. If the area affected is small then the surgeon may be able to remove the damaged portion and join the intestine back together. In instantances where the narrowing is longer, or the area is damaged and cannot be used for a period of time, a temporary stoma may be placed.