Large Colon Torsion - Horse

Large Colon Torsion is also known as Large colon Volvulus

Description

Large Colon Torsion results from the rotation of the organ about its axis. The degree of torsion dictates the severity of clinical signs and the speed at which the condition progresses. Volvulus can occur at any point along the colon; the most common site is the junction between the caecum and the right ventral colon, and most twist in a clockwise direction, when looking at the horse from behind.

The condition can be described as strangulating if the rotation is greater than 360°, causing vascular as well as luminal obstruction to the intestine. This form of torsion is more serious and acute in presentation, resulting in endotaemia and death within hours if treatment is not prompt.

Signalment

Post parturient mares, large breed horses and those with a history of dietary change or grazing on lush pasture are predisposed to the condition.

Diagnosis

Clinical Signs

• Signs of Colic
• Tachycardia
• Poor periferal pulse quality
• tachypnoea
• Abdominal distension

On rectal examination the colon is distented and tympanic, the mesentry is palpably oedematous and the colonic bands may be felt in a transverse orientation. See Colic Diagnosis in Horses

Laboratory Tests

Haemotology and Biochemistry reveal haemoconcebtration, changes in acid-base status and electrolyte abnormalities.

Ultrasound

Abdominal ultrasound reveals a distended large colon with thickened, oedematous walls. Peritoneal fluid should be sampled under ultrasound guidance, typical changes include an increase in protein and cellular content.

Treatment

Mild non-strangulating torsions can be managed conservatively but for more severe torsions and all strangulating torsions surgery is vital. Rapid referral for surgical correction is imperitive to maximise the chances of a good outcome.

In conjunction with surgical treatment, IV fluids will be needed to replace plamsa volume, and electrolyte abnormalities corrected. Antibiotic drugs, Polymixin B and NSAIDs with anti-endotoxic effects are indicated to minimise the damage from ischaemic intestine. See Medical Treatment of Colic in Horses

Prognosis

Prognosis depends on the degree of volvulous and the speed of diagnosis and treatment. Torsions of less than 270° have a good prognosis, for more severe torsions, those that are stragulating, or in cases where surgery has been delayed, the prognosis is poor.

References

• Mair, T.S, Divers, T.J, Ducharme, N.G (2002) Manual of Equine Gastroenterology, WB Saunders.
• Mair, T., Love, S., Schumacher, J. and Watson, E. (1998) Equine Medicine, Surgery and Reproduction WB Saunders Company Ltd
• Merck & Co (2008) The Merck Veterinary Manual (Eighth Edition) Merial
• Robinson, N.E., Sprayberry, K.A. (2009) Current Therapy in Equine Medicine (Sixth Edition) Saunders Elsevier
• White, N.A., Edwards, G.B. (1999) Handbook of Equine Colic Reed Educational and Professional Publishing Ltd