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

• Foreign bodies of all types can be found in the intestines.
• While some may pass through posing no problems, others can cause acute obstruction,
• Quite common in dogs
  • Rare in other species - tend to lodge in the oesophagus or in one of the ruminant stomachs.)
  • Enteroliths can be seen in horses greater than 4 years of age.
    • Are stones consisting of magnesium ammonium phosphate around a central nidus (often a metallic foreign body)
    • Typically lodge at the pelvic flexure or the transverse colon.
• Clinical
  • Obstruction at pylorus produces repeated vomiting.
  • Obstrustion lower down gives less dramatic effect.
    • Is still a problem if in the middle of the small intestines.
    • May be vague signs; some vomiting and off food.
• Diagnosis
  • May not show up well radiographically (unless radio-opaque) for several days.
    • May also be objects that are semi solid or soft, e.g.
      • String
      • Plastic bags
      • Stringy things, like pieces of material- particularly in puppies.
  • Make all of intestines have knotted appearance.
  • May be seen in horses with baler twine.
• Pathogenesis
  • Smooth, round objects, such as golf balls, lodge especially near the pylorus or lower down.
  • Occasionally in cattle (piece of rope or piece of tarpaulin) produces a tangled mass in rumen.
  • Cause pressure necrosis and eventually perforation.
  • Foreign bodies can also be chronic, remaining for long periods of time without causing disturbance.

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.