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Bowel obstruction

Last updated: January 24, 2020

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Bowel obstruction is the interruption of the normal passage of bowel contents either due to a functional decrease in peristalsis or mechanical obstruction. Functional bowel obstruction, or paralytic ileus, is a temporary disturbance of peristalsis in the absence of mechanical obstruction. Postoperative ileus is the most common cause of paralytic ileus, which can also be caused by metabolic disturbances (e.g., hypokalemia), endocrinopathies (e.g., hypothyroidism), and certain drugs (e.g., anticholinergics). Mechanical bowel obstruction is classified according to the location as either small bowel obstruction (SBO) or large bowel obstruction (LBO) and, depending on the severity of obstruction, as either partial or complete. The most common cause of SBO is postoperative bowel adhesions, while the most common cause of LBO is malignant tumors. Regardless of the cause, bowel obstruction typically manifests with nausea, vomiting, abdominal pain, abdominal distention, and constipation or obstipation. In paralytic ileus, bowel sounds are usually absent on auscultation, whereas a high-pitched tinkling sound would be heard in the early phase of a mechanical bowel obstruction. Bowel distention leads to third-space volume loss, resulting in dehydration and electrolyte abnormalities. Symptoms are less severe in partial bowel obstruction. Diagnosis is confirmed on imaging with contrast-enhanced CT scan and abdominal x-rays. Typical findings in mechanical bowel obstruction include dilated bowel loops proximal to the obstruction, collapse of bowel loops distal to the obstruction, and, on contrast-enhanced imaging, a cut-off or transition point at the site of obstruction. In paralytic ileus, findings include generalized dilatation of bowel loops with no transition point and air that is visible in the rectum. Additional laboratory tests include CBC and BGA for the assessment of infection, electrolyte imbalances (e.g., hypokalemia), and metabolic imbalances (e.g., alkalosis). Surgical intervention (i.e., exploratory laparotomy) is recommended for suspected closed-loop bowel obstruction, if there are signs of perforation or peritonitis, or if there is no improvement following conservative management. In all other cases, conservative treatment is usually successful and involves bowel rest, gastric decompression (nasogastric suction), fluid resuscitation, and correction of electrolyte abnormalities.

Mechanical bowel obstruction Paralytic ileus
Small bowel obstruction (SBO) Large bowel obstruction (LBO)
  • Interruption in the normal passage due to a structural barrier
  • Temporary impairment of peristalsis in the absence of a mechanical obstruction
  • Recent abdominal surgery
  • Atherosclerotic disease
  • Abdominal infections or inflammatory conditions
  • Certain medications (opioids, anticholinergics, antiparkinsonian agents)
Clinical features
  • Colicky abdominal pain
  • Vomiting
  • Obstipation or constipation
  • Abdominal distention
  • High-pitched, tinkling bowel sounds (early)
  • Absent bowel sounds (late)
  • Diffuse, continuous abdominal pain
  • Vomiting
  • Obstipation or constipation
  • Marked abdominal distention
  • Tympany on percussion
  • Absent bowel sounds
Findings on imaging
  • Dilated bowel loops proximal to obstruction
  • Collapsed bowel loops distal to obstruction
  • No air within rectum
  • Multiple air-fluid levels
  • Cause of obstruction (e.g., tumor)
  • Diffusely dilated small and large bowel loops
  • Air within rectum
  • No evidence of mechanical obstruction


Bowel obstruction

An interruption in the normal passage of bowel contents.


Degree of obstruction

  • Partial bowel obstruction: bowel obstruction in which passage of some intestinal content through the blocked segment is possible
  • Complete bowel obstruction: total interruption of the passage of intestinal contents
  • Closed loop obstruction: a type of complete mechanical bowel obstruction in which a segment of bowel is occluded at two contiguous points (e.g., volvulus)

Site of obstruction



Etiology [1] [6]

Small bowel obstruction Large bowel obstruction
Most common causes
Other causes
Specific to infants and children

Pathophysiology [7]

Clinical features [4][8][9]

Clinical features SBO LBO
Abdominal pain
  • Colicky, periumbilical
  • Colicky or constant
  • Late-onset
  • Initially bilious
  • Progresses to fecal vomiting (presence of feces in vomitus)
Constipation or obstipation
Abdominal distention
  • Typically less significant than in LBO
  • Early and significant abdominal distention
Examination findings

Partial bowel obstruction causes gradually progressive symptoms that are milder than those of complete obstruction. Obstipation is absent in partial bowel obstruction.


In the workup of suspected mechanical bowel obstruction, imaging allows for quick confirmation of the diagnosis as well as detection of conditions requiring immediate surgery (e.g., perforation). Laboratory tests may further help to assess the severity of the condition (e.g., electrolyte imbalance due to vomiting).

Laboratory tests

Imaging [10][11][12][13]

Abdominal series

Consists of erect and supine abdominal x-rays and an erect chest x-ray.

  • Indication: Best initial test in hemodynamically unstable patients or in resource-poor health centers
  • Findings
    • Dilatation of bowel loops proximal to the obstruction
      • 3-6-9 rule to define bowel dilatation on imaging
        • Small bowel dilatation if > 3 cm
        • Large bowel dilatation if > 6 cm
        • Cecal dilatation if > 9 cm
      • In SBO: The dilated loops are predominantly central.
      • In LBO (esp. distal LBO): The dilated loops are predominantly peripheral.
    • Minimal/no air within the bowel loops distal to the obstruction
    • Stepladder sign (x-ray)
      • Multiple air-fluid levels and a stacked appearance of dilated small bowel loops
      • Best seen on an erect abdominal x-ray

CT abdomen and pelvis

More sensitive than x-ray

  • Indications
    • With IV and oral contrast: Best initial test in hemodynamically stable patients with suspected partial bowel obstruction [14][15] [16]
    • With IV contrast: Indicated in patients with suspected complete bowel obstruction.
    • Non-contrast: Indicated in patients with contrast-allergy and suspected complete bowel obstruction.
  • Findings

MRI abdomen and pelvis (with and/or without IV contrast)[17] [16]

  • Indication: patients who have a contraindication for radiation exposure
  • Findings: similar to CT

Abdominal ultrasound

Barium or water-soluble contrast enema

  • Indication: in suspected distal LBO
  • Findings
    • Tapering of bowel lumen at the site of obstruction
      • Complete bowel obstruction: contrast would not be visible beyond obstruction
      • Partial bowel obstruction: a trickle of contrast would be visible beyond obstruction
    • Bird beak sign seen in volvulus
    • Apple core sign seen in colonic malignancy

When imaging with contrast (CT, enema) and perforation is expected, use water-soluble oral contrast.


Conservative management

  • Indications
    • Partial bowel obstruction cases
    • Complete bowel obstruction with no signs of ischemia/necrosis or signs of clinical deterioration
  • Measures
    • Fluid resuscitation, correction of electrolyte imbalance
    • Intestinal decompression: nasogastric tube insertion
    • Bowel rest (NPO)
    • Administration of IV analgesics and antiemetics
    • Gradual increase of oral intake, starting with clear fluids, can be initiated once the abdominal pain and distention subside and bowel sounds return to normal.
  • Etiology-specific treatments

Peristalsis-inducing medication (e.g., metoclopramide) is contraindicated in complete mechanical bowel obstruction.


  • Indications
    • Suspected bowel obstruction and hemodynamic instability or features of sepsis
    • Complete bowel obstruction with signs of ischemia/necrosis or clinical deterioration
    • Persistent partial obstruction (> 3–5 days)
    • Closed-loop obstruction
  • Procedure: exploratory laparotomy
    • Restoration of intestinal transit: depends on intraoperative findings
    • If bowel resection is required, the intervention may be carried out in a single procedure with anastomosis or permanent ostomy creation, or in a multistaged procedure with a temporary diverting ostomy.

Bowel obstruction requires a swift workup to establish whether emergent surgery is necessary!

Acute management checklist for mechanical bowel obstruction [4][5][18]




The differential diagnoses listed here are not exhaustive.

A change in the character of pain (colicky pain becoming continuous), rebound tenderness on examination, and/or signs of sepsis in a patient with bowel obstruction indicate the onset of complications and necessitate emergency surgical intervention!

We list the most important complications. The selection is not exhaustive.



The common causes of paralytic ileus can be memorized using “5 Ps”: Peritonitis, Postoperative, low Potassium, Pelvic and spinal fractures, and Parturition.[22]



Clinical features

  • Continuous (noncolicky) abdominal pain or discomfort
  • Nausea, vomiting
  • Abdominal distention
  • Percussion: tympany
  • Palpation: no tenderness unless peritonitis is present
  • Auscultation: bowel sounds are absent (silent abdomen) or decreased (early paralytic ileus)




  • Abdominal x-ray: best initial test
  • Abdominal CT: to rule out suspected mechanical bowel obstruction or if abdominal x-ray is inconclusive
    • Has the highest sensitivity and specificity for differentiating ileus from mechanical obstruction
    • Identifies uniformly distended loops with no transition point and no structural/mechanical cause



  1. Griffiths S, Glancy DG. Intestinal obstruction. Surgery. undefined; 35 (3): p.3. doi: 10.1016/j.mpsur.2016.12.005 . | Open in Read by QxMD
  2. Nobie BA, Talavera F. Small-Bowel Obstruction. In: Dronen SC, Small-Bowel Obstruction. New York, NY: WebMD. http://emedicine.medscape.com/article/774140-overview. Updated: January 20, 2015. Accessed: December 7, 2016.
  3. Smith DA, Nehring SM. Bowel Obstruction. NCBI. 2019 .
  4. Bordeianou L, Yeh DD, Soybel DI, Hockberger RS, Chen W. Epidemiology, clinical features, and diagnosis of mechanical small bowel obstruction in adults. In: Post TW, ed. UpToDate. Waltham, MA: UpToDate. https://www.uptodate.com/contents/epidemiology-clinical-features-and-diagnosis-of-mechanical-small-bowel-obstruction-in-adults.Last updated: June 21, 2016. Accessed: December 7, 2016.
  5. Jackson PG, Raiji MT. Evaluation and Management of Intestinal Obstruction. American Family Physician. 2011; 83 (2): p.159-165.
  6. Editors: Donald W Kufe, MD, Raphael E Pollock, MD, PhD, Ralph R Weichselbaum, MD, Robert C Bast, Jr, MD, Ted S Gansler, MD, MBA, James F Holland, MD, ScD (hc), and Emil Frei, III, MD. Holland-Frei Cancer Medicine. BC Decker ; 2003
  7. Intestinal Obstruction. https://www.msdmanuals.com/professional/gastrointestinal-disorders/acute-abdomen-and-surgical-gastroenterology/intestinal-obstruction. Updated: December 1, 2018. Accessed: May 3, 2019.
  8. Yeh DD, Bordeianou L. Overview of mechanical colorectal obstruction. In: Post TW, ed. UpToDate. Waltham, MA: UpToDate. http://www.uptodate.com/contents/overview-of-mechanical-colorectal-obstruction.Last updated: August 31, 2015. Accessed: February 28, 2017.
  9. Stepladder sign (small bowel obstruction). https://radiopaedia.org/articles/stepladder-sign-small-bowel-obstruction-1. Updated: February 28, 2017. Accessed: February 28, 2017.
  10. Small bowel obstruction. https://radiopaedia.org/articles/small-bowel-obstruction. . Accessed: May 3, 2019.
  11. Large bowel obstruction. https://radiopaedia.org/articles/large-bowel-obstruction?lang=us. . Accessed: May 3, 2019.
  12. Cartwright SL, Knudson MP. Diagnostic Imaging of Acute Abdominal Pain in Adults. American Academy of Family Physicians. 2015; 91 (7): p.452-9.
  13. Bowel obstruction. https://radiopaedia.org/articles/bowel-obstruction. Updated: January 1, 2018. Accessed: May 13, 2019.
  14. American College of Radiology ACR Appropriateness Criteria® Suspected Small-Bowel Obstruction. https://acsearch.acr.org/docs/69476/Narrative/. Updated: January 1, 2013. Accessed: June 3, 2019.
  15. American College of Radiology ACR Appropriateness Criteria® Acute Nonlocalized Abdominal Pain. https://acsearch.acr.org/docs/69467/Narrative/. Updated: January 1, 2018. Accessed: March 30, 2018.
  16. Macaluso C, McNamara. Evaluation and management of acute abdominal pain in the emergency department. International Journal of General Medicine. 2012 : p.789. doi: 10.2147/ijgm.s25936 . | Open in Read by QxMD
  17. Cahalane MJ. Overview of gastrointestinal tract perforation. In: Post TW, ed. UpToDate. Waltham, MA: UpToDate. http://www.uptodate.com/contents/overview-of-gastrointestinal-tract-perforation.Last updated: March 1, 2016. Accessed: February 28, 2017.
  18. Retroperitoneal haemorrhage. https://radiopaedia.org/articles/retroperitoneal-haemorrhage. Updated: February 28, 2017. Accessed: February 28, 2017.
  19. Hopkins C. Large-Bowel Obstruction. Large-Bowel Obstruction. New York, NY: WebMD. http://emedicine.medscape.com/article/774045. Updated: December 14, 2016. Accessed: February 28, 2017.
  20. Paralytic ileus (mnemonic). https://radiopaedia.org/articles/paralytic-ileus-mnemonic. . Accessed: May 16, 2019.
  21. Bordeianou L, Daniel Dante Yeh DD, Soybel DI, Chen W. Overview of management of mechanical small bowel obstruction in adults. In: Post TW, ed. UpToDate. Waltham, MA: UpToDate. https://www.uptodate.com/contents/overview-of-management-of-mechanical-small-bowel-obstruction-in-adults.Last updated: May 18, 2016. Accessed: December 7, 2016.
  22. Ileus. https://online.epocrates.com/diseases/99531/Ileus/Diagnostic-Approach. . Accessed: May 3, 2019.
  23. Acute Abdomen - Practical approach. http://www.radiologyassistant.nl/en/p42d54f75d111d/acute-abdomen-practical-approach.html#i42d58779024fb. . Accessed: May 3, 2019.
  24. Adynamic ileus. https://radiopaedia.org/articles/adynamic-ileus. . Accessed: May 3, 2019.
  25. Landercasper J, Cogbill TH, Merry WH, et al. Long-term Outcome After Hospitalization for Small-Bowel Obstruction. Arch Surg. 1993; 128 (7): p.765-771. doi: 10.1001/archsurg.1993.01420190059008 . | Open in Read by QxMD
  26. Batke, Cappell. Adynamic Ileus and Acute Colonic Pseudo-Obstruction. The Medical Clinics of North America. undefined; 92 : p.649–670. doi: 10.1016/j.mcna.2008.01.002 . | Open in Read by QxMD
  27. Herold G. Internal Medicine. Herold G ; 2014
  28. Jaffe T, Thompson WM. Large-Bowel Obstruction in the Adult: Classic Radiographic and CT Findings, Etiology, and Mimics. Radiology. 2015; 275 (3): p.651-663. doi: 10.1148/radiol.2015140916 . | Open in Read by QxMD
  29. Walls R, Hockberger R, Gausche-Hill M. Rosen's Emergency Medicine. Elsevier Health Sciences ; 2018
  30. Gavriilidis P, de’ Angelis N, Tobias A. To Use or Not to Use Opioid Analgesia for Acute Abdominal Pain Before Definitive Surgical Diagnosis? A Systematic Review and Network Meta-Analysis. Journal of Clinical Medicine Research. 2019; 11 (2): p.121-126. doi: 10.14740/jocmr3690 . | Open in Read by QxMD
  31. Ten Broek RPG, Krielen P, Di Saverio S, et al. Bologna guidelines for diagnosis and management of adhesive small bowel obstruction (ASBO): 2017 update of the evidence-based guidelines from the world society of emergency surgery ASBO working group. World Journal of Emergency Surgery. 2018; 13 (1): p.24. doi: 10.1186/s13017-018-0185-2 . | Open in Read by QxMD
  32. Di Saverio S, Coccolini F, Galati M, et al. Bologna guidelines for diagnosis and management of adhesive small bowel obstruction (ASBO): 2013 update of the evidence-based guidelines from the world society of emergency surgery ASBO working group. World Journal of Emergency Surgery. 2013; 8 (1): p.42. doi: 10.1186/1749-7922-8-42 . | Open in Read by QxMD
  33. Pisano M, Zorcolo L, Merli C, et al. 2017 WSES guidelines on colon and rectal cancer emergencies: obstruction and perforation. World Journal of Emergency Surgery. 2018; 13 (1): p.36. doi: 10.1186/s13017-018-0192-3 . | Open in Read by QxMD
  34. Maung AA, Johnson DC, Piper GL, et al. Evaluation and management of small-bowel obstruction. Journal of Trauma and Acute Care Surgery. 2012; 73 (5): p.S362-S369. doi: 10.1097/ta.0b013e31827019de . | Open in Read by QxMD
  35. Rami Reddy SR, Cappell MS. A Systematic Review of the Clinical Presentation, Diagnosis, and Treatment of Small Bowel Obstruction. Curr Gastroenterol Rep. 2017; 19 (6): p.28. doi: 10.1007/s11894-017-0566-9 . | Open in Read by QxMD
  36. Jackson P, Vigiola Cruz M. Intestinal Obstruction: Evaluation and Management.. Am Fam Physician. 2018; 98 (6): p.362-367.
  37. Li Z, Zhang L, Liu X, Yuan F, Song B. Diagnostic utility of CT for small bowel obstruction: Systematic review and meta-analysis.. PLoS ONE. 2019; 14 (12): p.e0226740. doi: 10.1371/journal.pone.0226740 . | Open in Read by QxMD
  38. Mian M, Swamy N, Angtuaco T. Imaging in Acute Intestinal Obstruction. Contemporary Diagnostic Radiology. 2019; 42 (24): p.1-7. doi: 10.1097/01.cdr.0000612380.42855.c0 . | Open in Read by QxMD
  39. Diamond M, Lee J, LeBedis CA. Small Bowel Obstruction and Ischemia. Radiol Clin North Am. 2019; 57 (4): p.689-703. doi: 10.1016/j.rcl.2019.02.002 . | Open in Read by QxMD
  40. Bower KL, Lollar DI, Williams SL, Adkins FC, Luyimbazi DT, Bower CE. Small Bowel Obstruction. Surg Clin North Am. 2018; 98 (5): p.945-971. doi: 10.1016/j.suc.2018.05.007 . | Open in Read by QxMD
  41. Hayden GE, Sprouse KL. Bowel Obstruction and Hernia. Emerg Med Clin North Am. 2011; 29 (2): p.319-345. doi: 10.1016/j.emc.2011.01.004 . | Open in Read by QxMD
  42. Fonseca AL, Schuster KM, Maung AA, Kaplan LJ, Davis KA. Routine nasogastric decompression in small bowel obstruction: is it really necessary?. Am Surg. 2013; 79 (4): p.422-8.
  43. Harrison ME, Anderson MA, Appalaneni V, et al. The role of endoscopy in the management of patients with known and suspected colonic obstruction and pseudo-obstruction. Gastrointest Endosc. 2010; 71 (4): p.669-679. doi: 10.1016/j.gie.2009.11.027 . | Open in Read by QxMD
  44. Long B, Robertson J, Koyfman A. Emergency Medicine Evaluation and Management of Small Bowel Obstruction: Evidence-Based Recommendations. J Emerg Med. 2019; 56 (2): p.166-176. doi: 10.1016/j.jemermed.2018.10.024 . | Open in Read by QxMD
  45. Manterola C, Vial M, Moraga J, Astudillo P. Analgesia in patients with acute abdominal pain. Cochrane Database of Systematic Reviews. 2011 . doi: 10.1002/14651858.cd005660.pub3 . | Open in Read by QxMD
  46. Sugawa C. Endoscopic management of foreign bodies in the upper gastrointestinal tract: A review. World Journal of Gastrointestinal Endoscopy. 2014; 6 (10): p.475. doi: 10.4253/wjge.v6.i10.475 . | Open in Read by QxMD
  47. Franke AJ, Iqbal A, Starr JS, Nair RM, George TJ. Management of Malignant Bowel Obstruction Associated With GI Cancers. Journal of Oncology Practice. 2017; 13 (7): p.426-434. doi: 10.1200/jop.2017.022210 . | Open in Read by QxMD
  48. Beyer D, Mödder U. Diagnostic Imaging of the Acute Abdomen. Springer Berlin Heidelberg ; 1988
  49. Pourmand A, Dimbil U, Drake A, Shokoohi H. The Accuracy of Point-of-Care Ultrasound in Detecting Small Bowel Obstruction in Emergency Department. Emergency Medicine International. 2018; 2018 : p.1-5. doi: 10.1155/2018/3684081 . | Open in Read by QxMD
  50. Taylor MR, Lalani N. Adult Small Bowel Obstruction. Academic Emergency Medicine. 2013; 20 (6): p.527-544. doi: 10.1111/acem.12150 . | Open in Read by QxMD
  51. Alzaraa A, Krzysztof K, Uwechue R, Tee M, Selvasekar C. Apple-core lesion of the colon: a case report. Cases J. 2009; 2 (1): p.7275. doi: 10.4076/1757-1626-2-7275 . | Open in Read by QxMD