Small Bowel Obstruction

Quick Hit:

  • Etiology:
    • Most common = Adhesions (post-abdominal surgery)
    • Other causes = hernia, malignancy, intraluminal stricture, intussusception, foreign body, duodenal hematoma
  • Symptoms
    • colicky/paroxysmal abd pain w/ episodic, hyperactive bowel sounds, diffuse abd tenderness, bilious vomit
    • failure to pass stool or flatus = signs of complete bowel obstruction
  • Diagnosis: dilated loops on x-ray, dilated fluid filled loops (air-fluid levels) on CT Abdomen
  • Management:
    • IV fluid resuscitation w/ electrolyte repletion
    • Complete obstruction, or signs of peritonitis = surgical emergency
    • Partial obstruction: non-operative management (NG tube decompression, close observation)
  • Complications: strangulation
    • Signs of strangulation = metabolic acidosis from lactic acidosis secondary to ischemic necrosis caused by strangulation

UPDATED (10/1/12):  Ultrasound podcast docs back at it with update on SBO:


Podcast lecture on SBO

Rick Martin – Small Bowel Obstruction
Courtesy of Free Emergency Talks

Small bowel obstruction (SBO) is a common condition seen in the emergency department, and therefore accounts for large percentage of surgical admissions. While the diagnosis of SBO can often be made by history and physical exam, the lack of specificity of any of the symptoms make it difficult to exclude other differentials without further studies.

The etiology of most small bowel obstructions is related to postoperative adhesions and hernias. This sets up the perfect setting in the peritoneal cavity for the flow of intestinal contents to be interrupted. Without the history of surgery or hernia, other less common etiologies of SBO must be ruled out including malignancies and strictures. Obstructions lead to the stomach and small bowel proximal to the occlusion to become dilated, while the segments of bowel distal to the obstruction will collapse. Significant complication of the dilated bowel is related to the compromise of blood flow. This leads to complications such as necrosis, strangulation, and sepsis.

The difficulty in the management of SBO relates to properly diagnosing the severity of the obstruction and the necessity of surgery. There unfortunately are no early reliable signs of strangulation, with metabolic acidosis being a later sign when the strangulation has progress to necrosis.

Obstructions can be classified in a variety of manners. Descriptors include: mechanical vs. nonmechanical, potential need for operation (immediate, urgent, delayed, or no surgery), acute versus chronic, partial versus complete, simple versus closed loop, and gangrenous versus nongangrenous. When chyme and gas can traverse the point of obstruction, obstruction is partial; when this is not the case, obstruction is complete. When the bowel is occluded at a single point along the intestinal tract, it is classified as a simple loop. Closed loop obstructions can be described “segment of bowel is occluded at two points along its course by a single constrictive lesion that occludes both the proximal and the distal end of the intestinal loop and traps the bowel’s mesentery” [ source = ACS surgery]


Preliminary studies for SBO include chest and abdominal x-ray and CT-scan of abdomen. Chest x-rays are suggested to exclude pneumonic process and look for subdiaphragmatic air. Abdominal radiographs can be normal in patients with complete, closed-loop, or strangulation obstructions. Other imaging modalities with higher sensitivity and specificity are suggested if patient’s clinical profile and historical risk factors make obstruction high on the differential despite normal radiographs. CT scan is the imaging test of choice, with abdominal ultrasonography gaining popularity as well.

Evidence Based Medicine:

A recent Cochrane review studied using Gastrografin transit time to assist in selecting patients w/ non operative management. With some studies showing the timing and amount of contrast reaching the colon on serial radiographs can help distinguish complete obstruction vs. partial obstruction. Other studies have also shows that giving water soluble contrast can be therapeutic to resolving the obstruction. Their conclusions find:

This review addresses two questions. First, “Does the oral administration of water soluble contrast media followed by serial abdominal radiographs during the following 24 hours predict the need for early operation or resolution?”

Second, “Does the administration of water soluble contrast media in patients with adhesive small bowel obstruction facilitate the resolution of symptoms and shorten hospital stay?”

Six studies that addressed the first question were included. The pooled results indicated that oral gastrografin is a very accurate predictor of non operative resolution of adhesive small bowel obstruction with a sensitivity of 0.97, specificity of 0.96 and area under the ROC curve of 0.98. Five studies addressed the second question were included, although Gastrografin does not reduce the need for surgery it does reduce hospital stay in those patients who do not require surgery.

Oral water soluble contrast for the management of adhesive small bowel obstruction, Saleh Abbas, Ian P Bissett and Bryan R Parry. DOI: 10.1002/14651858.CD004651.pub3

Management of SBO is summarized in the following chart from ACS Surgery: Principles & Practice.

A recent prospective study (2011) echos some older articles showing the equally favorable efficacy of ultrasonography as compared to x-ray in the diagnosis of SBO.

How to use sonography for SBO diagnosis is well described from the guys (including UK’s own Dr. Dawson!) at ultrasound podcast:

Sources and Additional information:

  • 2012. ACS Surgery: Principles & Practice. Hamilton, Ontario & Philadelphia, PA. Decker Publishing Inc. ISSN 1547-1616. STAT!Ref Online Electronic Medical Library.
  • Abbas S, Bissett IP, Parry BR. Oral water soluble contrast for the management of adhesive small bowel obstruction. Cochrane Database of Systematic Reviews 2007, Issue 3. Art. No.: CD004651. DOI: 10.1002/
  • Oral water soluble contrast for the management of adhesive small bowel obstruction, Saleh Abbas, Ian P Bissett and Bryan R Parry. DOI: 10.1002/14651858.CD004651.pub3
  • Bedside ultrasonography for the detection of small bowel obstruction in the emergency department Jang TB, Schindler D, Kaji AH.
  • UpToDate for images

Compiled by: Sakib Motalib

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