Intestine: obstruction

• 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  .
• Simple obstructions can be high (proximal), and involve the pylorus, duodenum and the proximal jejunum. A low (distal), small bowel obstruction involves the lower one-half of the jejunum and ileum.
• Cause:
  • Foreign bodies   Intestine: foreign body - linear  .
  • Tumors (lymphosarcoma   Lymphoma  , annular adenocarcinoma).
  • Strictures due to trauma or prior surgery.
  • Intussusception   Intussusception  .
  • Abscesses or adhesions (rarely).
• Signs: variable but may include dehydration, hypovolemic shock   Shock  , endotoxic shock   Shock: septic  , and death.
• Diagnosis: radiography.
• Treatment: usually surgical intervention.
• Prognosis: higher mortality rates are associated with strangulation and high obstructions.

• Vomiting   Vomiting  .
• Dehydration.
• Hypovolemic shock   Shock  .

Distal non-strangulated

• Anorexia.
• Weight loss.

• Intermittent vomiting.
• Death, (chronic cases).

• Severe clinical signs.
• Fever or hypothermia.
• Abdominal pain or tenderness.
• Palpable abdominal mass.
• Incarcerated bowel in hernia.
• Endotoxic shock   Shock: septic  .
• Death.

• Young: more likely to play with novel objects.

• Cost of surgery.

• Foreign bodies   Intestine: foreign body - linear  .
• Tumors (lymphosarcoma, annular adenocarcinoma)   Small intestine: neoplasia  ,   Large intestine: neoplasia  .
• Strictures due to trauma or prior surgery.
• Intussusception   Intussusception  .
• Abscesses.
• Adhesions.

• Distension of the bowel begins proximal to the obstruction, thus causing fluid and gas accumulation.
• The content of the fluid will depend upon the location of the obstruction.

• Large foreign body   →   ulceration and pressure necrosis.

Proximal obstruction

• High intramural pressure   →   compromized 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 to the 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 due to lactic acidosis.

Distal obstruction

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

• Acute: proximal and strangulated obstruction.
• Chronic: low obstruction.

• Vomiting   Vomiting  .
• Shock   Shock  .
• Abdominal mass.

• Vomiting.
• Anorexia.
• Weight loss.

• Death.

• Dehydration.
• Hypovolemic shock.
• Endotoxic shock.
• Abdominal pain.
• Abdominal mass.

• See abdominal radiography   Radiography: abdomen  , for technique.
• Radiopaque foreign body.
• Gas and fluid accumulation proximal to obstruction.
• Linear foreign bodies; pleated pattern and eccentric gas bubbles   Intestine: foreign body - linear  ,     ,     .
• Intussusception; soft tissue mass   Intussusception  ,     .
• Strangulated obstruction (+hernia); loops of intestine outside peritoneal cavity   Intestine: strangulated obstruction / hernia    Small intestine: neoplasia  .

Hematology

• Typically neutrophilia may be leukopenia in endotoxic shock   Hematology: complete blood count (CBC)  .

Biochemistry

• Electrolyte abnormalities common due to vomiting and fluid pooling in intestine   Blood biochemistry: overview  .
• Monitor sodium   Blood biochemistry: sodium  , potassium   Blood biochemistry: potassium  , chloride   Blood biochemistry: chloride  , acid base balance.

Contrast radiography

• See gastrography   Radiography: gastrography  .
• To visualize radiolucent foreign body (FB) or obstruction     .

• See GI ultrasonography   Ultrasonography: GI system  .
• May be able to visualize multilayered sections of intestine indicative of intussusception     .

Other

• Laparotomy/celiotomy to visualize obstruction   Laparotomy: midline  .

• Other causes of acute vomiting:
  • Infectious, eg panleukopenia   Feline panleucopenia virus disease  .
  • Gastritis   Chronic gastritis  - traumatic, irritant, allergic.
  • Uremia   Uremia  .
  • Poisoning.
• Obstruction due to other cause:
  • Neoplasia   Small intestine: neoplasia  ,   Large intestine: neoplasia  .
  • Intussusception   Intussusception  .

• Fluid therapy to stabilize animal prior to surgery   Fluid therapy: overview  .

• Surgery   Laparotomy: midline    Intestine: linear foreign body removal  .

• Electrolytes.

Monitoring

• Post-operative peritonitis   Peritonitis  , and enterotomy.
• For development of stricture at site of repair.

• Excellent in acute cases with rapid surgical correction.
• Guarded if chronic obstruction, particularly if intestine perforated.
• Cessation of vomiting.
• Breakdown of surgical repair.
• Pre-existing peritonitis.
• Bacteria breach intestine wall   →   endotoxic shock.

Refereed papers

• Recent references from PubMed and VetMedResource.
• Barrs V R, Beatty J A, Tisdall P L et al (1999) Intestinal obstruction by trichobezoars in five cats. J Fel Med Surg 1 (4), 199-207 PubMed.