ISSN 2398-2969      

Megacolon: acquired

icanis
Contributor(s):

Ken Harkin

James Simpson


Introduction

  • Distended, hypomotile colon leading to severe constipation.
  • Cause:
    • Loss of motor function to colon - atonic.
    • Secondary to obstruction to passage of feces.
    • Idiopathic.
    • Congenital.
  • Signs: lethargy, anorexia, constipation, ptyalism, vomiting, tenesmus.
  • Diagnosis: abdominal palpation, confirmed by abdominal radiographs.
  • Treatment: initially - fluid therapy, remove cause, laxatives and enemas; long-term - by dietary modification and laxative; rarely successful so require surgical correction.
  • Prognosis: guarded depending on stage of disease and choice of treatment.

Pathogenesis

Etiology

  • Often idiopathic - dysfunction of colonic smooth muscle, progressive post-receptor defect in excitation-contraction coupling.
  • Secondary to colonic obstruction:
    • Extraluminal compression, eg pelvic fracture.
    • Intraluminal masses or strictures.
    • Functional disorders, eg neuromuscular disease.
    • Congenital anomalies.
    • Metabolic disorders.

Specific

  • Colonic neoplasia, eg adenocarcinoma/lymphosarcoma.
  • Foreign bodies.
  • Extramural colonic compression.
  • Strictures.

Pathophysiology

  • Failure of motor function or obstruction to passage of feces → loss of colonic motor activity → normal defecation prevented over prolonged period → colon distends → further muscle degeneration → colon flaccid and filled with dry, hard fecal material → further damage to myenteric neural plexus → hypomotility.
  • Idiopathic.

Timecourse

  • Variable.

Diagnosis

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Treatment

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Outcomes

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Further Reading

Publications

Refereed papers

Other sources of information

  • Williams J (1996)Surgical management of conditions of the gastrointestinal tract and associated glands.In:Manual of canine and feline gastroenterology.BSAVApp 221-253.
  • Brightet al(1986)Bilateral colectomy.In:Treatment of acquired megacolon in the dog and cat.JAVMA188, 1412-1416.

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