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Colon: torsion

pequis

Synonym(s): Strangulating colonic displacement, Large colon volvulus (LCV)


Introduction

  • Dorsal and ventral loops of the large colon rotate about a common axis (mesocolon).
  • Cause: large colon is mobile; torsion may be initiated by movement of left dorsal colon, pelvic flexure, and/or left ventral colon.
  • Signs: depend on degree of torsion and vascular and luminal obstruction.
  • Diagnosis: clinical signs, rectal examination and exploratory laparotomy/post-mortem examination.
  • Treatment: surgical correction.
  • Prognosis: good up to 180°, fair 180-270°, guarded to 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, or newly created space in the abdomen (such as the case post-foaling).
  • 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 (though this scenario is uncommon).

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 pressure leading to difficulty ventilating.
  • 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 (based on location).
  • Torsions may comprise up to 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.
  • Gonzalez L M, Baker W T, Hughes F E, Blikslager A T & Fogle C A (2020) Comparison of histomorphometric characteristics of dorsal colon and pelvic flexure biopsy specimens obtained from horses with large colon volvulus that underwent resection. Am J Vet Res 81 (11), 899-903 PubMed.
  • Orr K E, Baker W T, Lynch T M et al (2020) Prognostic value of colonic and peripheral venous lactate measurements in horses with large colon volvulus. Vet Surg 49 (3), 472-479 PubMed.
  • Broyles A H, Hopper S A, Woodie J B & Ruggles A J (2018) Clinical outcomes after colopexy through left ventral paramedian incision in 156 thoroughbred broodmares with large colon disorders (1999-2015). Vet Surg 47 (4), 490-498 PubMed.
  • Leahy E R, Holcombe S J, Hackett E S, Scoggin C F & Embertson R M (2018) Reproductive careers of Thoroughbred broodmares before and after surgical correction of 360 degree large colon volvulus. Equine Vet J 50 (2), 208-212 PubMed.
  • Hackett E S, Embertson R M, Hopper S A, Woodie J B & Ruggles A J (2015) Duration of disease influences survival to discharge of Thoroughbred mares with surgically treated large colon volvulus. Equine Vet J 47 (6), 650-4 PubMed.
  • Fiege J K, Hackett E S, Rao S, Gillette S C & Southwood L L (2015) Current treatment of ascending colon volvulus in horses: a survey of ACVS Diplomates. Vet Surg 44 (3), 398-401 PubMed.
  • Gonzalez L M, Fogle C A, Baker W T et al (2015) Operative factors associated with short-term outcome in horses with large colon volvulus: 47 cases from 2006 to 2013. Equine Vet J 47 (3), 279-84 PubMed.
  • Hurcombe S D, Welch B R, Williams J M, Cooper E S, Russell C & Mudge M C (2014) Dark-field microscopy in the assessment of large colon microperfusion and mucosal injury in naturally occurring surgical disease of the equine large colon. Equine Vet J 46 (6), 674-80 PubMed.
  • Sanchez L C & Robertson S A (2014) Pain control in horses: What do we really know? Equine Vet J 46 (4), 517-523 PubMed.
  • 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.

Other sources of information

  • Southwood L L (2019) Large Colon. In: Equine Surgery. 5th edn. Ed: Auer J & Stick J. Saunders, USA. pp 591-621,

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