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    Bowel Obstruction


    Last Updated Feb 17, 2022
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    • Bowel obstruction occurs when the normal flow of intraluminal contents is interrupted.
    • Classification of bowel obstruction includes functional (due to abnormal intestinal physiology, ie. postoperative ileus) or mechanical, partial or complete, and acute or chronic.
    • With respect to location, the distribution of small and large bowel obstructions is estimated to be 75% and 25% of cases, respectively.
    • Acute mechanical small bowel obstruction accounts for 2-4% of emergency department visits, 15% of hospital admissions, and 20% of emergency surgical interventions for abdominal pain.


    • In the United States and Western Europe, the most common causes of mechanical small bowel obstruction are intraperitoneal adhesions, tumors, and incarcerated hernias.
    • Less frequent causes of obstruction include Crohn disease, gallstones, volvulus, and intussusception.

    Clinical Presentations and Risk Factors

    • Most patients with small bowel obstruction will present acutely with an abrupt onset of colicky abdominal pain, nausea, vomiting, and abdominal distention.
    • One study found that the absence of passage of flatus (90%) and/or feces (80.6%) and abdominal distension (65.3%) were the most common symptoms and physical exam findings in bowel obstruction, respectively.
    • Risk factors for obstruction include:
      • Prior abdominopelvic surgery.
      • Abdominal wall or groin hernia.
      • Intestinal inflammation.
      • Prior abdominopelvic irradiation.
      • Foreign body ingestion.

    Physical Examination and Laboratory Investigations

    • Physical examination should include evaluation for systemic signs of dehydration or sepsis, abdominal inspection, auscultation, percussion, and palpation, as well as a digital rectal examination.
    • Typical laboratory investigations for patients presenting with abdominal pain include complete blood count with differential, electrolytes, BUN, and creatinine.
    • In patients presenting with systemic signs of illness (ie. fever, tachycardia, hypotension, altered mental status), additional laboratory investigation should include:
      • Arterial blood gas.
      • Serum lactate (specificity = 42-87%, sensitivity = 90-100% for ischemia in small bowel obstruction.)
      • Blood cultures (metabolic acidosis can occur with bowel ischemia or severe hypovolemia causing hypoperfusion of other organs.)

    Diagnostic Process

    • Abdominal imaging is required to confirm the diagnosis, identify the location of obstruction, judge whether the obstruction is partial or complete, identify complications related to obstruction, and determine the etiology.
    • Plain abdominal radiography is the initial imaging modality of choice to rapidly confirm the diagnosis, followed by contrast-enhanced CT of the abdomen and pelvis to further characterize the obstruction (provided the plain films do not have findings that indicate the need for immediate intervention.)
    • Plain films should include an upright chest film and upright and supine abdominal films to look for dilated bowel loops (> 2.5 cm), air-fluid levels (>3), and free air under the diaphragm on upright films suggesting perforation.


    • Complications of bowel obstruction include bowel compromise (ischemia, necrosis, and perforation) and sepsis.
    • CT findings suggestive of bowel ischemia include:
      • Poor or absent bowel wall enhancement.
      • Bowel wall thickening.
      • Gas in the bowel wall (pneumatosis intestinalis.)
    • Pneumoperitoneum is a sign of perforation and may be detected as:
      • Free air under the diaphragm on upright chest or upright abdominal radiography.
      • Free air over the spleen or liver on a lateral abdominal film or abdominal CT.
      • Free air as a “football sign” on a supine abdominal film or abdominal CT.

    Recommended Treatment

    • Bowel compromise, clinical signs of deterioration (fever, leukocytosis, tachycardia, peritonitis) or a surgically correctable cause of bowel obstruction (ie. incarcerated hernia, volvulus, NOT adhesions) require immediate surgical exploration, while other patients may be candidates for a trial of non-operative management.
    • 60-85% of adhesion-related small bowel obstructions resolve without surgery.
    • All patients with bowel obstruction require admission to the hospital and prompt surgical consultation to determine if immediate surgical intervention is needed.
    • Initial management:
      • NPO.
      • Fluid resuscitation.
      • Electrolyte repletion.
      • NG tube decompression for patients with significant distension, nausea, or vomiting.
    • Antibiotics:
      • Not indicated for most patients with uncomplicated small bowel obstruction.
      • Indicated for patients with suspected bowel compromise or inflammatory/infectious causes of non-adhesive obstruction.
    • For adhesive small bowel obstruction with no CT indications for immediate surgery, consider a Gastrografin challenge.
      • Hypertonic water-soluble contrast agent administered via NG tube; may be therapeutic.
      • Obtain abdominal radiographs 6-24 hours after administration → evidence of Gastrografin reaching the colon is predictive of resolution without surgical intervention.
      • Note: Gastrografin is contraindicated in pregnancy.

    Criteria For Hospital Admission

    • All patients with bowel obstruction should be admitted to the hospital.

    Criteria For Transfer To Another Facility

    • Dependent on resource availability.

    Criteria For Close Observation And/or Consult

    • All patients with bowel obstruction need prompt surgical consultation to determine if immediate surgical intervention is needed.

    Related Information

    Reference List


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