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Emergency: requires immediate attention
Small bowel obstruction
Other Resources UpToDate PubMed
Emergency: requires immediate attention

Small bowel obstruction

Contributors: Brit Long MD, Taylor Reffett MD, Michael W. Winter MD, Sara Manning MD
Other Resources UpToDate PubMed


Emergent Care / Stabilization:
  • Obtain urgent surgical consultation and administer early antibiotics for patients presenting with signs of bowel ischemia or sepsis.
  • Give fluid resuscitation to patients presenting with hypovolemia or signs of shock, with pressors as needed.
  • Provide symptomatic therapy with intravenous (IV) pain medication and antiemetics.
  • Give the patient nothing by mouth.
  • Gastric decompression with a nasogastric tube (NGT) is not recommended in all cases but may assist in patients with severe abdominal distension.
Diagnosis Overview:
A small bowel obstruction (SBO) occurs when intraluminal bowel contents fail to pass through the small intestine. Impaired passage of bowel contents results in dilation of the proximal bowel, with fluid accumulation, gas production, increased intraluminal pressure, and bacterial overgrowth. This results in abdominal distension and pain, nausea, and vomiting, with risk of bowel ischemia and perforation.

SBOs are defined by the etiology (mechanical or functional) and severity (complete or partial).

Common etiologies include:
  • Postoperative adhesions (most common)
  • Incarcerated or strangulated hernia (second most common)
  • Midgut volvulus
  • Intussusception
  • Tumors
  • Intraluminal foreign bodies, such as gallstones
  • Compression from extraluminal masses
A thorough history, including any history of prior abdominal surgeries, radiation, malignancy, or inflammatory bowel disorders can assist in determining the etiology.

SBOs can be classified as partial or complete. Partial SBOs permit some passage of bowel contents past the obstruction site, while complete SBOs are associated with the inability to pass any gas or fluid past the obstruction. Partial SBOs can further be stratified into high-grade or low-grade, depending on the severity of obstruction, with low-grade SBOs presenting with less severe symptoms. A simple SBO is characterized by a single point of obstruction. A closed-loop obstruction is characterized by occlusion of the bowel at 2 points and has the highest risk of ischemia due to occlusion of the blood supply.

Patients most commonly present with diffuse or periumbilical abdominal pain, often described as colicky, with paroxysms every few minutes. Pain may become localized or constant if the bowel becomes ischemic or perforated. Abdominal distension is highly suggestive, as is constipation. Patients commonly have nausea and vomiting, which varies in severity based on the location of the obstruction, with proximal SBOs presenting with more severe symptoms. Patients with complete obstructions stop passing stool or flatus, although this may be delayed for 12-24 hours as the bowel distal to the obstruction continues to pass contents. Rarely, patients may have intermittent obstruction, often partial and low-grade, with spontaneous resolution of symptoms between episodes.

The greatest concern from an SBO is the risk of increased dilation leading to necrosis and bowel perforation. Patients with bowel ischemia or perforation typically present with more severe signs and symptoms, often with evidence of peritonitis, sepsis, and hemodynamic instability.


K56.609 – Unspecified intestinal obstruction, unspecified as to partial versus complete obstruction

281255004 – Small bowel obstruction

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Diagnostic Pearls

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Differential Diagnosis & Pitfalls

  • Intestinal ileus – Commonly occurs immediately after abdominal surgery or trauma. Imaging will show air in the colon and rectum.
  • Intestinal pseudo-obstruction (Ogilvie syndrome) – Most commonly occurs in older adults with multiple comorbidities, often with severe illness. Imaging will also show air in the colon and rectum, often with marked distension.
  • Intussusception – Patients are usually younger than 2 years, with paroxysms of pain lasting 15-20 minutes at a time.
  • Large bowel obstruction – Most commonly due to malignancy. Patients may present with a subacute course of disease.
  • Viral gastroenteritis – Abdominal pain is less prominent, and the abdomen is soft, although there may be mild diffuse tenderness.
  • Appendicitis – Abdominal pain may be located in the periumbilical area before migrating to the right lower quadrant (RLQ), with localized tenderness.
  • Cholecystitis – Abdominal tenderness is usually localized to the right upper quadrant (RUQ), with a positive Murphy's sign. Patients may have a history of gallstones or RUQ pain in the past, particularly after fatty food ingestion.
  • Acute pancreatitis – Pain is more likely to be in the epigastrium and may radiate to the back. Serum lipase levels are usually elevated.
  • Intestinal perforation – Patients have peritoneal signs with guarding and/or rebound tenderness and typically display evidence of sepsis (eg, fever, tachycardia). SBO can result in intestinal perforation.

Best Tests

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Management Pearls

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Drug Reaction Data

Below is a list of drugs with literature evidence indicating an adverse association with this diagnosis. The list is continually updated through ongoing research and new medication approvals. Click on Citations to sort by number of citations or click on Medication to sort the medications alphabetically.

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Last Reviewed:01/11/2023
Last Updated:01/19/2023
Copyright © 2023 VisualDx®. All rights reserved.
Emergency: requires immediate attention
Small bowel obstruction
A medical illustration showing key findings of Small bowel obstruction (Acute) : Abdominal pain, Nausea, Vomiting, Abdominal distension, Constipation, Periumbilical pain, BUN elevated, HR increased, BP decreased, WBC elevated, Cr elevated
Imaging Studies image of Small bowel obstruction - imageId=7879387. Click to open in gallery.  caption: '<span>CT scan of the abdomen and  pelvis demonstrating a dilated cecum with "whirl sign," which is made up  of twisted bowel and mesocolon, consistent with cecal volvulus resulting in small bowel obstruction. </span>'
CT scan of the abdomen and pelvis demonstrating a dilated cecum with "whirl sign," which is made up of twisted bowel and mesocolon, consistent with cecal volvulus resulting in small bowel obstruction.
Copyright © 2023 VisualDx®. All rights reserved.