Category:Intestine - Mechanical Obstruction

• Acute of chronic mechanical obstruction of the intestine can occur in all species.
  • Acute obstruction usually involves the upper or middle small intestine
  • Chronic obstruction typically occurs in the distal small intestine or large intestine.
• Three main categories of causes of obstruciton:
  • Intraluminal
    • E.g. foreign bodies, food impaction.
  • Intramural
    • E.g. neoplasia
  • Extrinsic
    • E.g. adhesions, neoplasia and prostate enlargement.

Intraluminal Obstruction

Foreign Bodies, Intestinal

Impaction

• Impaction of the colon can occur in all species.
  • Dog and cat - main cause is dehydrated faecal material.
  • Horse - faeces, digesta, sand, or fibrous material can all contribute.
    • There are certain predisposing factors:
      • Poor dentition
      • Water deprivation
      • A high roughage diet
      • General debility.
• Antihelminthic administration or large parasite burdens can also lead to impaction.

Extrinsic Obstruction

• Obstruction of the intestine due to external factors such as tumours, abscesses, and fibrous adhesions is a common occurrence.

Inflammatory Adhesions

colonic adhesions in the horse (Courtesy of Elspeth Milne)

• Arise following gut perforation, peritonitis or surgery.
• Consist of fibrous tissue bands that may:
  • Restrict intestinal motility
  • Cause kinks in the mesentery.

Prostatic Enlargement

• In the dog
• Can lead to compression of the rectum

Neoplasia

• Neoplasi in structures adjacent to the intestines can spread and cause external compression.
• Pancreatic tumours in particular can extend and impinge on the duodenum.
• Pedicles of tumours such as lipomas in horses can become wound in loops of intestine leading to obstruction and possible strangulation.

Closeup of a pedunculated lipoma (Courtesy of Elspeth Milne)

• Clinical
  • Occasional vomiting and ntermittent diarrhoea over several weeks.
• Pathogenesis
  • Seen occasionally in cat (rarer in dog)
  • Usually towards end of intestines
    • E.g. at the ileocaecocolic valve.
  • Gut proximal to tumour becomes thickened due to hypertrophy of smooth muscle as a result of trying to force ingesta past progessively narrowing lumen.
  • Produces "hose pipe intestine".
  • Seen with carcinoma, lymphoma, leiomyoma and other tumours.