Canis ISSN: 2398-2942

Intestine: obstruction

Synonym(s): Obstipatiocoli, Intestinal blockage, Intestinal foreign body

Contributor(s): Ken Harkin, James Simpson

Introduction

  • Bowel obstruction is a frequent occurrence and is the most common indication for surgical intervention involving the gastrointestinal tract. Classified as simple (mechanical or functional) or strangulated Intestine: strangulated obstruction (hernia).
  • Cause: foreign bodies, tumors (lymphosarcoma Lymphoma , annular adenocarcinoma Adenoma / adenocarcinoma ), strictures due to trauma or prior surgery, intussusception, abscesses or adhesions (rarely).
  • Signs: variable depending on location of obstruction - may include vomiting, dehydration, abdominal pain, endotoxic shock, perforation, death.
  • Diagnosis: plain radiography usually adequate but not for radiolucent causes.
  • Obstructions can be high (proximal) involving the pylorus, duodenum and the proximal jejunum or low (distal) small bowel obstruction involving the lower half of the jejunum and ileum.
  • Treatment: surgery.
  • Prognosis: higher mortality rates are associated with strangulation and high obstructions Intestine: strangulated obstruction (hernia).

Pathogenesis

Etiology

Pathophysiology

  • Obstruction interferes with passage of luminal contents along the intestine.
  • Distention of bowel occurs proximal to obstruction with fluid and/or gas and food.
  • Foreign bodies may cause damage which varies according to their shape and size:
    • Laceration.
    • Obstruction.
    • Pressure necrosis.
    • Perforation.

Proximal obstruction

  • High intramural pressure → compromised blood supply → possible shunting away from intestinal capillaries to arteriovenous anastomoses → hypoxia to the bowel, loss of viability and increased permeability to toxins, including endotoxins.
  • Duodenum is more sensitive to circulatory changes associated with distension.

Obstruction proximal at pylorus

  • Hydrogen ion loss → metabolic alkalosis often with hypokalemia.

Obstruction below the pancreatic and biliary ducts

  • Vomiting and loss of absorption of fluid collecting proximal to the obstruction → rapid and severe losses with significant amount of bicarbonate ion → dehydration and/or hypovolemic shock → metabolic acidosis.

Distal obstruction

  • Fluid and electrolyte losses less severe but significant in chronic cases.
  • Less severe distension of intestinal wall → circulation of affected gut unimpeded.

Strangulation

  • Partial or total obstruction of venous drainage and an intact arterial supply → intramural sequestration of blood and eventually bowel wall edema.
  • Distended bowel proximal to the strangulation filled with gas and fluid containing a significant amount of blood → non-viable and necrotic bowel wall → transmural migration of toxins and bacteria → hypovolemia, endotoxic shock and death.

Timecourse

  • Hours to days for acute obstruction.
  • Partial or intermittent obstructions may show signs over weeks to months.

Diagnosis

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Treatment

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Prevention

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Outcomes

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Further Reading

Publications

Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Graham J P, Lord P F & Harrison J M (1998) Quantitative estimation of intestinal dilation as a predictor of obstruction in the dogJSAP 39 (11), 521-4 PubMed.
  • Shaiken L (1997) Determining the type of intestinal obstruction. Vet Med 92 (11), 950-951 VetMedResource.


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