Category:Obstruction, Intestinal

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Obstruction, Intestinal

Intestinal obstruction can be the sequel to either mechanical or functional causes. Mechanical obstruction occurs due to physical blockage of the intestinal lumen whereas functional obstruction results from a decrease or inhibition of intestinal motility due to loss of smooth muscle contraction (Brown et. al, 2007).


Category:Intestine - Mechanical Obstruction

Functional Obstruction

Paralytic Ileus

  • A common condition.
  • Occurs following trauma or abdominal surgery.
  • Stasis of gut flow due to failure of peristalsis.
    • Leads to distension with gas and fluid, as well as a flaccid intestinal wall.
Causes
  • Anything which stops peristalsis, e.g.
    • Damage to nerve supply to intestine (autonomic nervous system)
    • Pain
    • Abnormal metabolism
    • Toxaemia
    • Electrolyte imbalance such as hypocalcaemia, hypomagnesaemia, and hypokalaemia.
  • Also in
    • Diabetes mellitus
    • Uraemia
    • Tetanus
    • Lead poisoning.
Pathology
  • loss of smooth muscle tone leads to a flaccid bowel.
  • Bowel is distended with fluid.
Pathogenesis
  • Intestine susceptible to neurogenic damage during an operation.
  • Peristalsis fades away over a few days producing paralytic (adynamic) ileus.
  • Particularly occurs if bowel handled roughly, or if serosa gets cold and dry at surgery.
  • Very difficult to start peristalsis again but will sometimes respond to pharmacological or electrical stimulation.
  • The horse is very susceptible, and the dog is somewhat suscpeitble.

Dysautonomia

  • Most notably affects horses and cats.
Equine dysautonomia, or grass sickness
  • Most prevalent in the UK and western Europe.
    • Common in wetter areas, e.g. the South West.
  • Seen in horses out at pasture in late summer and autumn.
  • Usually affects young adults.
    • 6-7 years old.
  • Clinical
    • Acute oneset:
      • Muscular tremors
      • Abdominal pain
      • Does not eat
      • Constipation
      • Become severly tympanic in acute cases
      • Dull and restless
      • Avoid swallowing
      • Salivate excessively
    • Degenerative lesions are seen in the autonomic nerve ganglia, including enteric plexuses
    • May either:
      • Progress rapidly to death
      • Take a slower clinical course.
        • Eat a bit, but food drops out of mouth
        • Go on to die slowly.
    • Some horses recover
      • This is very unlikely, and the condition is usually fatal.
    • Clinically difficult to diagnose - signs are confined to the gut.
      • Easy to diagnose on post mortem
  • Pathology
  • Pathogenesis
    • Due to functional obstruction at ileocaecal valve and a degree of paralytic ileus of the small intestine.
    • The exact cause is unknown, but a type of bacterial or fungal toxin which may damage autonomic nervous system ganglia may be involved.
  • A similar condition seen in hares
    • Certain yeares almost seem to have outbreaks.
  • Certain pastures at certain times of year produce grass sickness quite often.
    • A definitive diagnosis must be made - if the condition is due to the grazing we need to know.
      • E.g. if on livery or stud grazing, may put people off going there.
  • 'Diagnosis
    • At post mortem look for degenerative changes in coeliaco-mesenteric ganglia - need to examine histologically.
      • Ganglia are peanut sized and found in perirenal fat between adrenal gland and the aorta.
Feline dysautonomia, or Key-Gaskell Syndrome
Histological section of degenerate neuron in feline dysautonomia(Courtesy of Susan Rhind)
  • Occurs mostly in the UK and continental Europe.
  • Is also of unknown aetiology. Suggested causative factors include:
    • Environmental toxins
    • Infectious agents
    • Botulinum toxins .
  • Clinical signs:
    • Anorexia
    • Depression
    • Bradycardia
    • Decreased lacrimation,
    • Altered pupillary dilataion,
    • Megaoesophagus
    • Constipation.
  • Degenerative lesions of autonomic nerve ganglia can be seen.
  • Also occurs in the oesophagus.

Subcategories

This category has the following 2 subcategories, out of 2 total.