Bowel obstruction, also known as intestinal obstruction, is a mechanical or functional obstruction of the intestines that prevents the normal movement of the products of digestion. Either the small bowel or large bowel may be affected. Signs and symptoms include abdominal pain, vomiting, bloating and not passing gas. Both sexes are equally affected and the condition can occur at any age. Bowel obstruction has been documented throughout history, with cases detailed in the Ebers Papyrus of 1550 BC and by Hippocrates.

Signs and symptoms

Depending on the level of obstruction, bowel obstruction can present with abdominal pain, abdominal distension, and constipation. 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 ischemia or perforation from prolonged distension or pressure from a foreign body and subsequently sepsis due to bowel flora.

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 may occur before constipation.

In large bowel obstruction, the pain is felt lower in the abdomen and the spasms last longer. Common symptoms include abdominal pain, distension, and severe constipation. Constipation occurs earlier and vomiting may be less prominent. Proximal obstruction of the large bowel may present as small bowel obstruction.)

  • Barbed sutures
  • Pseudoobstruction
  • Hernias containing bowel
  • Crohn's disease causing adhesions or inflammatory strictures
  • Neoplasms, benign or malignant
  • Intussusception
  • Volvulus
  • Superior mesenteric artery syndrome, a compression of the duodenum by the superior mesenteric artery and the abdominal aorta
  • Ischemic strictures
  • Foreign bodies (e.g. gallstones in gallstone ileus, swallowed objects such as expandable water toys)
  • Intestinal atresia
  • Urinary retention

After abdominal surgery, the incidence of small bowel obstruction from any cause is 9%. In those where the cause of the obstruction was clear, adhesions are the single most common cause; in developed countries, about three-quarters of all small bowel obstructions are caused by postoperative adhesions.

Large bowel obstruction

thumb|upright|Upright abdominal X-ray of a person with a large bowel obstruction showing multiple air fluid levels and dilated loops of bowel

Causes of large bowel obstruction include:

  • Neoplasms / cancer
  • Diverticulitis / Diverticulosis
  • Hernias
  • Inflammatory bowel disease
  • Colonic volvulus (sigmoid, caecal, transverse colon)
  • Adhesions
  • Constipation
  • Fecal impaction
  • Fecaloma
  • Colon atresia
  • Intestinal pseudoobstruction
  • Endometriosis
  • Narcotic induced (especially with the large doses given to cancer or palliative care patients)

Outlet obstruction

Outlet obstruction is a sub-type of large bowel obstruction and refers to conditions affecting the anorectal region that obstruct defecation, specifically conditions of the pelvic floor and anal sphincters. Outlet obstruction can be classified into four groups.

  • Functional outlet obstruction
  • Inefficient inhibition of the internal anal sphincter
  • Short-segment Hirschsprung's disease
  • Chagas disease
  • Hereditary internal sphincter myopathy
  • Inefficient relaxation of the striated pelvic floor muscles
  • Anismus (pelvic floor dyssynergia)
  • Multiple sclerosis
  • Spinal cord lesions
  • Mechanical outlet obstruction
  • Internal intussusception
  • Enterocele
  • Dissipation of force vector
  • rectocele
  • Descending perineum
  • Rectal prolapse
  • Impaired rectal sensitivity
  • Megarectum
  • Rectal hyposensitivity

Diagnosis

{| class="wikitable floatleft"

|+ Small bowel dilation on CT scan in adults

! Diameter !! Assessment

|-

| <2.5&nbsp;cm || Non-dilated

|-

| 2.5-2.9&nbsp;cm || Mildly dilated

|-

| 3–4&nbsp;cm || Moderately dilated

|-

| >4&nbsp;cm || Severely dilated

|}

thumb|A small bowel obstruction as seen on CT

thumb|Average inner diameters and ranges of different sections of the large intestine.

The main diagnostic tools are blood tests, X-rays of the abdomen, CT scanning, and ultrasound. If a mass is identified, biopsy may determine the nature of the mass.

Radiological signs of bowel obstruction include bowel distension (small bowel loops dilated >3&nbsp;cm) and the presence of multiple (more than 2) air-fluid levels on supine and erect abdominal radiographs. Ultrasounds may be as useful as CT scanning to make the diagnosis.

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. The appearance of water-soluble contrast in the cecum on an abdominal radiograph within 24 hours of it being given by mouth predicts resolution of an adhesive small bowel obstruction with sensitivity of 97% and specificity of 96%.

Colonoscopy, small bowel investigation with ingested camera or push endoscopy, and laparoscopy are other diagnostic options.

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File:UOTW 20 - Ultrasound of the Week 1.webm|Small bowel obstruction on ultrasound

File:UOTW 20 - Ultrasound of the Week 2.webm|Small bowel obstruction on ultrasound

Treatment

Treatment of small and large bowel obstructions are initially similar and non-operative management is usually the initial management strategy as the majority of small bowel obstruction resolve spontaneously with non-operative management. Patients are monitored by the surgical team for signs of improvement and resolution of the obstruction on imaging; if the obstruction does not clear then surgical management for the treatment of the causative lesion is 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. Diagnosis of the type of bowel obstruction is normally conducted through initial plain radiograph of the abdomen, luminal contrast studies, computed tomography scan, or ultrasonography prior to determining the best type of treatment.

Further research is needed to find out if parenteral nutrition is of benefit to people with an inoperable blockage of the bowel caused by advanced cancer.

Small bowel obstruction

In the management of small bowel obstructions, a commonly quoted surgical aphorism is: "never let the sun rise or set on small-bowel obstruction" because about 5.5%

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 but alternate pain relievers are preferred as opioids can decrease bowel motility.

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.

Prognosis

The prognosis for non-ischemic cases of SBO is good with mortality rates of 3–5%, while prognosis for SBO with ischemia is fair with mortality rates as high as 30%.

Cases of SBO related to cancer are more complicated and require additional intervention to address the malignancy, recurrence, and metastasis, and thus are associated with a more poor prognosis.

All cases of abdominal surgical intervention are associated with increased risk of future small-bowel obstructions. Statistics from U.S. healthcare report 18.1% re-admittance rate within 30 days for patients who undergo SBO surgery. More than 90% of patients also form adhesions after major abdominal surgery. Common consequences of these adhesions include small-bowel obstruction, chronic abdominal pain, pelvic pain, and infertility.