Intestinal Obstruction

Signalment

Can affect any breed or sex.

Description

Intestinal obstruction can be classified as acute or chronic, partial or complete, simple or incarcerated. The cause of the obstruction can be intraluminal, extraluminal or intramural. Most common causes of intestinal obstruction include intussusception, neoplasia and foreign body. Intussusception is more likely in young animals with a history of gastroenteritis or intestinal surgery. Cats frequently present with linear foreign bodies. Other less common causes include intestinal torsion/volvulus and incarcerated intestinal obstruction. Neoplasia is more commonly present in middle-aged to older animals.

Diagnosis

Clinical Signs

The clinical presentation depends on cause, severity, and site of obstruction. Upper small intestinal obstruction causes a net fluid secretion whereas lower small intestinal obstruction causes a net fluid resoption. Antibiotic responsive diarrhoea is more likely in distal small intestinal obstruction.

Simple obstruction

Vomiting; the further the obstruction is towards the mouth, the more frequent and the more volume the vomiting is
Moribund or in septic shock; if part of the intestine becomes devitalised, resulting in septic peritonitis
Abdominal foreign body, mass or obstructive ileus may be palpable

Incarcerated intestinal obstruction

Acute vomiting
Abdominal pain
Depression
Endotoxic shock with toxic mucous membranes and tachycardia

Intestinal torsion/volvulus

Acute and severe onset of:

nausea
retching
vomiting ± bloody diarrhoea
acute abdomen
abdominal fluid accumulation
depression

Linear foreign body

Vomiting; food, bile and/or phlegm
Anorexia, depression

Laboratory Tests

Haematology

Mild dehydration to septic shock

Biochemistry

Hypochloraemia and hypokalaemia acid-base derangement is common in animals with intestinal obstruction.
Metabolic alkalosis ± aciduria may occur with upper duodenal obstruction.

Diagnostic Imaging

Radiography

Plain abdominal radiography may be all that is needed to reveal the cause of the obstruction. Gas and fluid accumulation may be visible due to intestinal dilation. Decreased serosal detail indicates peritoneal fluid accumulation and free gas in the abdomen suggests perforated intestines. Gravel sign due to food particle accumulation amay be present. Displacement, bunching or plication may also be seen.
Contrast radiography may be needed if ileus and obstruction cannot easily be distinguished. However, this may not always be feasible in an emergency situation

Ultrasonography

Most of the time, this is a more sensitive technique in revealing the cause of the obstruction compared to radiography. Dilation and thickening of the wall of the intestine may be visible.

Histopathology

Fine needle aspirate may be warranted before surgery if a mass is suspected, such as lymphoma.

Treatment

Stabilisation

Fluid balance, electrolyte and acid-base derangements are common in a vomiting animal. These need to be addressed prior to anaesthesia.

Antimicrbial

Broad spectrum antimicrobials, such as a ampicillin or cephalosporin combined with metronidazole, are usually given prophylactically prior to surgery. This is vital if there are signs of sepsis or intestinal compromise.

Surgery

Once stabilised, the animal can be taken to surgery. Removal or resection of the obstruction is required.

Prognosis

This depends on type and severity of obstruction. A simple obstruction with no signs of septic peritonitis has a good prognosis. A better prognosis in cases where there is no large resection of the intestines. On the other hand, the prognosis is grave if there are signs of metastatic neoplasia.

References

Ettinger, S.J. and Feldman, E. C. (2000) Textbook of Veterinary Internal Medicine Diseases of the Dog and Cat Volume 2 (Fifth Edition) W.B. Saunders Company.
Hall, E.J, Simpson, J.W. and Williams, D.A. (2005) BSAVA Manual of Canine and Feline Gastroenterology (2nd Edition) BSAVA
Nelson, R.W. and Couto, C.G. (2009) Small Animal Internal Medicine (Fourth Edition) Mosby Elsevier.