ISSN 2398-2977      

Colon: torsion

pequis

Synonym(s): Strangulating colonic displacement


Introduction

  • Dorsal and ventral loops of the large colon rotate about a common axis.
  • Cause: large colon is mobile; torsion may be initiated by movement of left dorsal colon.
  • Signs: depend on degree of torsion and vascular and luminal obstruction.
  • Diagnosis: clinical signs, rectal examination and exploratory laparotomy/post-mortem examination.
  • Treatment: some resolve spontaneously (up to 180°), others require surgery.
  • Prognosis: good up to 180°, fair 180-270°, poor with greater degree of torsion. In the case of strangulating torsions, prognosis is maximized by prompt surgical treatment.

Pathogenesis

Etiology

  • Large colon is relatively mobile.
  • Twisting of the colon may be initiated by presence of impacted material or excessive intraluminal gas.
  • Torsion may occur in either hypomotile or hypermotile states.
  • Torsion may be clockwise (more common) or anticlockwise.
  • Undesirable fermentation processes   →   gas accumulation may cause colon to "float".
  • Colonic volvulus has been reported in association with mesenteric defects or abnormal anatomical structures.

Predisposing factors

General

Specific

  • Brood mares in late gestation/early postpartum period (complete torsion common):
    • Large feed intake during winter expands colon.
    • Potential space in abdomen following pregnancy.
  • Hypomotile intestine.
  • Hypermotile intestine.
  • Gas accumulation.

Pathophysiology

  • Dorsal and ventral loops of colon rotate about a common axis   →   effects vary depending on degree of torsion.
  • Degree of torsion varies from <90° to >360°. The latter are strangulating torsions   →   rapid ischemic necrosis.
  • Length of strangulated loop varies: left dorsal and left ventral only   →   usually non-strangulating ("partial") torsions; complete (often strangulating) torsions occur either at origin of large intestine and may or may not involve the cecum.
  • Circulatory impairment depends on degree of torsion and distension with food and gas   →   tympany   →   severe respiratory compromise and pressure on great vessels   →   diaphragmatic rupture in some cases.
  • Occlusion of veins but not arteries   →   congestive hyperemia and extravasation into intestinal wall and abdominal cavity   →   edema of gut wall and mesocolon   →   mucosal necrosis and bleeding into lumen   →   fluid loss of 60-80 l into extracellular space in 4-6 h   →   endotoxemia   →   death usually occurs before colonic rupture.

Timecourse

  • Strangulating torsion usually fatal in 6-12 h.

Epidemiology

  • Incidence of torsions 11-17% of surgical colic cases.
  • Torsions comprise nearly 40% of surgical colics involving large colon.
  • Relatively common in brood mares during post-partum period.

Diagnosis

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Treatment

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Prevention

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Outcomes

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Further Reading

Publications

Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Knowles E J & Mair T S (2009) Colonic volvulus with defects of the mesenteric attachments in a yearling Friesian colt. Equine Vet Educ 21 (8), 396-400 VetMedResource.
  • Groover E S, Woolums A R, Cole D J & LeRoy B E (2006) Risk factors associated with renal insufficiency in horses with primary gastrointestinal disease: 26 cases (2000-2003). JAVMA 228 (4), 572-577 PubMed.
  • Proudman C J, Edwards G B, Barnes J & French N P (2005) Modeling long-term survival of horses following surgery for large intestinal disease. Equine Vet J 37 (4), 366-370 PubMed.
  • Pease A P, Scrivani P V, Erb H N & Cook V L (2004) Accuracy of increased large-intestinal wall thickness during ultrasonography for diagnosing large colon torsion in 42 horses. Vet Radiol Ultrasound 45 (3), 220-224 PubMed.
  • Southwood L L (2004) Post-operative management of the large colon volvulus patient. Vet Clin North Am Equine Pract 20, 167-197 PubMed.
  • Schumacher J (2001) Treatment of a horse following rupture of the colon during surgery. Equine Vet Educ 13 (1), 13-16 VetMedResource.
  • Darien B J, Stone W C, Dubielzig R R & Clayton M K (1995) Morphologic changes of the ascending colon during experimental ischemia and reperfusion in ponies. Vet Pathol 32 (3), 280-288 PubMed.
  • Mair T S & Lucke V M (1992) Chyloperitoneum associated with torsion of the large colon in a horse. Vet Rec 131 (18), 421 VetMedResource.
  • Ross M W & Bayha R (1992) Volvulus of the cecum and large colon caused by multiple mesenteric defects in a horse. JAVMA 200 (2), 203-204 PubMed.

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