Equis ISSN 2398-2977

Gastrointestinal: fecalith / bezoar

Contributor(s): Peter Rakestraw

Introduction

  • Fecaliths and phytobezoars are masses that build up in the intestinal system, particularly the right dorsal colon.
  • Cause: usually form as concretions around foreign bodies or food material.
  • Signs: include colic, although they may be non-pathogenic, they can cause partial obstructions, particularly at the entrance to the transverse colon, and within the small colon if they move.
  • Diagnosis: rectal palpation, or at laparotomy.
  • Treatment: surgical removal.
  • Prognosis: good, provided prompt treatment is carried out when necessary.

Pathogenesis

Etiology

  • They usually have a foreign body nidus such as a nail/piece of wire.
  • They are slow growing, but can reach large sizes.

Predisposing factors

General
  • Breed - miniature horses.
  • Intestinal foreign bodies.
  • Diet high in alfalfa, which allows intestinal pH to rise, thereby promoting the formation of fecoliths.

Pathophysiology

  • Masses develop in the intestines, particularly the right dorsal colon.
  • They rarely cause problems there, though they may cause low-grade intermittent, chronic colic due to progressive partial obstruction of the gut lumen.
  • They may move into the entrance to the transverse colon and cause colic due to partial obstruction in this situation.
  • They may move into the narrower small colon and cause complete obstruction.
  • Complete obstruction results in the development of signs of severe colic that requires surgery.
  • Partial intermittent obstruction of the colonic lumen results in blockage of the intestinal transit. Mild pain can result due to stretching of the bowel.
  • In cases involving complete obstruction of the colonic lumen, the pathologic mechanisms are as follows:
    • Stasis of intestinal fluid proximal to the obstruction results in the multiplication of intestinal bacteria and the release of gas.
    • Increased pressure within the bowel due to fluid and gas build up causes distension, which results in an increase in pain, as well as a decrease in peristalsis.
    • The result is progressive filling and swelling of the gut, and atonia of the gut wall.
    • Without treatment, progressive damage to the intestinal wall occurs, with degeneration, cell sloughing, and vascular compromise.
    • Endotoxins and bacteria leak into the bloodstream and peritoneal cavity, causing damage to epithelial cells and platelets.
    • Platelets release thromboxane and serotonin causing vasoconstriction.
    • Endothelial cell damage causes the stimulation of neutrophils.
    • Endotoxemia may result, and this can cause further sensitization of the pain receptors.
    • Electrolyte and fluid sequestration contribute to the development of circulatory collapse.
    • Hypovolemia, endotoxic shock, electrolyte and acid/base abnormalities develop.
    • Pain due to the stretching of proximal bowel wall, as well as to gut and vascular compromise at the site of the lesion is generally continuous, and shows no, or only temporary response to analgesics.
    • Cardiovascular compromise is reflected by tachycardia, a decrease in pulse quality, mucous membrane congestion or cyanosis, and an increase in capillary refill time. Secondary increases in packed cell volume (PCV) and plasma proteins (TPP) are seen, and metabolic acidosis causes tachypnoea.
  • In cases that involve colonic rather than small intestinal obstruction, the development of clinical signs is gradual, and the resulting pain is usually mild, until severe bowel wall compromise is present.

Timecourse

  • Even when complete bowel obstruction occurs, it may take several hours for severe signs to develop.

Diagnosis

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Treatment

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Outcomes

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Further Reading

Publications

Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Cummings C A, Copedge K E & Confer A W (1997)Equine gastric impaction, ulceration and perforation due to persimmon (Diospyros virginiana) ingestion.J Vet Disgn Invest9(3), 311-313 PubMed.
  • Edwards G B (1997)Diseases and surgery of the small colon.Vet Clin North Am Equine Pract13(2), 359-375 PubMed.
  • Yvorchuk-St Jean K Eet al(1993)Trichophytobezoar as a cause of transverse colon obstruction in a horse.JAVMA198(2), 295-296 PubMed.
  • Bohanon T C (1988)Duodenal impaction in a horse.JAVMA192(3), 365-366 PubMed.


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