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Bowel Obstruction

Study guide:


  • Paralytic ileus/adynamic bowel: failure to move the luminal contents due to poor motility.

  • Simple bowel obstruction: blockage of the bowel lumen at one area without complications (perforation, strangulation etc.).

  • Closed-loop obstruction: afferent and efferent bowel blockage, which usually results in complicated bowel obstruction and strangulation. 


Clinical Presentation: 

  • Nausea, vomiting, abdominal pain or distention, obstipation, and decreased flatus:

    • High SBO obstruction:
      1. Little evidence of dilated bowl loops on radiology

      2. Minimal distention.

      3. Bilious vomiting (early).

    • Low SBO:

      1. Abdominal pain referred to periumbilical area.

      2. Vomiting is delayed

      3. Multiple dilated bowl loops on radiology

    • LBO obstruction:

      1. Obstipation and abdominal distension (early).

      2. Abdominal pain referred to the lower abdominal area.

      3. Distended colon proximal to the obstruction on radiology  

  • Fever: might be seen with strangulation.

  • Abdominal tenderness and guarding: seen with strangulation and perforation. 

Bloody emesis/vomiting with the other bowel obstruction S&S strongly suggests strangulation!



  • Mainly clinical.

  • Abdominal series (Upright abdominal, supine abdominal, and upright chest plain film X-ray):

    1. Supine abdominal is the most important.

    2. Upright abdominal is usually used to check for Air-fluid level.

    3. Upright chest is done to check for Pneumoperitoneum.

  • Barium Swallow or Enema.

  • CT: usually for SBO.

  • Lab tests:

    1. CBC: to check for leukocytosis, hemoglobin, and BUN.

    2. Blood chemistries: potassium & sodium.

    3. ABGs: to check for metabolic acidosis, or alkalosis. 

Cardinal features of ACUTE SBO: Ab. Pain (colicky, central) Distension Vomiting Absolute constipation 

Metabolic alkalosis is usually seen with pyloric obstruction or SBO. Metabolic acidosis is seen with late presentation of bowel obstruction. 


  • Conservative medical therapy:

    1. Keep the patient NPO.

    2. IV hydration and correct the electrolyte imbalances.

    3. NG tube:

      • ​To prevent aspiration of vomitus.

      • To decompress the small bowel.

  • Foley catheter: to monitor the urine output, and so monitor hydration.

  • Surgical Management:

    • True bowel obstruction is considered as a surgical emergency, and those patients are candidates for laparotomy.

      • Early surgical intervention

        1. Obstructed external hernia

        2. Suspicion of strangulation

        3. Obstruction in a virgin (not operated on) abdomen

      • Exceptions:

        1. Partial obstruction.

        2. History of multiple previous laparotomies.

        3. Severely debilitated patient.

    •  Antibiotic coverage for gram-negative organisms. 

    • Post-operative care:

      1. Continue NG tube until the bowel function is resumed.

      2. Continue antibiotics if the patient is septic, wound contamination, long-standing peritonitis.

      3. Start total parental nutrition (TPN) if the bowel function is not resumed after 5 days. 

The six questions you should know about any obstruction: 

1- Is it obstruction or not? (presence of cardinal symptoms; e.g. vomiting, constipation, bowel obstruction...) 

2- What is the likely level of obstruction? (prominent symptoms; e.g. vomiting -> proximal, abdominal distention -> distal) 

3- What is the likely underlying cause of obstruction? 

4- Is the obstruction complete (not passing gas or stool) or partial (only passing gas)? 

5- Is the obstruction simple or complicated? (e.g. signs of strangulation) 

6- Does the patient suffer from any physiological changes?(e.g. signs of dehydration, electrolyte disturbances...)

1- Is it obstruction or not? (presence of cardinal symptoms; e.g. vomiting, constipation, bowel obstruction...) 


  • Reid M, Stehr W. The Mont Reid surgical handbook.

  • Kumar P, Clark M. Kumar & Clark's clinical medicine.

  • Bowel Obstruction - Causes and Pathophysiology [Internet]. YouTube. 2016 [cited 13 April 2016]. Available from:

  • Le T, Bhushan V, Singh Bagga H. First aid for the USMLE step 2 CK. New York: McGraw-Hill Medical; 2010.

  • Baily and Love’s short practice

  • Clinical surgery

  • Essential surgery 



Written by:     Roaa Amer

Reviewed by:    Areej Madani
                          Haifa Al Issa

Format Editor:  Reem AlQarni

Web Publisher:  Abdullah K. Al Johani

                           Bayan Alzomaili

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