Intestinal Arterial Thromboembolism

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  • Non-strangulation infarction.
  • There is often a functional obstruction at point of infarction.
  • Relatively rare as the bowel has a good anastomosing blood supply.
Thrombosis of cranial mesenteric artery caused by Strongylus vulgaris larvae (Courtesy of Bristol BioMed Image Archive)

Horses

  • E.g. Strongylus vulgaris larvae migrating in cranial mesenteric artery in horse
    • Cause arteritis with thickening of wall
      • Due to fibrin and debris deposition and hypersensitivity reaction
    • Leads to vasoconstriction
      • May occlude lumen and encourage thromboemboli.
    • Can cause ischaemic necrosis of a segment of small intestine
    • Is less common now that Strongylus vulgaris infections are declining.
  • E.g. equine salmonellosis.
Infarction of the small bowel (Courtesy of Bristol BioMed Image Archive)

Verminous endarteritis

  • Caused by larvae of S. vulgaris within the cranial mesenteric artery
  • Also called "verminous aneurism" (misnomer as aneurism = dilatation/thinning of blood vessel wall; also, aneurisms are rare)
  • Wall of artery grossly thickened (organising thrombi, inflammatory responses)
  • Can be detected on rectal palpation
  • Many cases asymptomatic
  • May get embolism → infarction of areas of intestinal wall → colic or chronic ulceration (note: generally good collateral circulation; therefore colic is not inevitable)
  • Aberrant larvae may cause thrombosis in other arteries; e.g. iliac, cerebral, coronary
  • Avermectin/milbemycins or fenbendazole are used to control migrating S. vulgaris larvae


Small Animals

  • Especially dogs
  • Road traffic accidents produce and infact in the gut.
  • Renal disease also causes infarction.
    • Particularly nephrotic syndrome.
    • Anticoagulant proteins are lost in the urine, leading to a prothrombic state in the ciruclation.

Pathology

  • Similar to that caused by venous congestion.
  • See sharply delineated dark areas in bowel that are flaccid with loss of tone.
    • These become necrotic followed later by peritonitis.