Intussusception - Horse

Description

An intussusception is an invagination or 'telescoping' of a length of intestine (the intussusceptum) into an adjacent, more distal segment (the intussuscipiens). The small intestine is the most common site for this to occur and the affected segment may range in length from a few centimeters up to a metre. Intussuception in the horse most commonly involves the ileum (ileo-caecal or ileo-ileal). Jejuno-jejunal intussusceptions also occur in the horse but they are considerably less common.

The aetiology of the condition is not fully understood, but is thought to be due to underlying disorders of gut motility. This may be due to one of several conditions including parasitism, enteritis, use of anthelmintics and surgical trauma.

Signalment

Small intestinal intussusceptions can occur in horses of all ages but those aged between six months to three years are most commonly affected. There is no breed or sex predilection.

Clinical signs

Clinical signs are dependent on whether the obstruction caused by the intussusception is partial or complete. Complete obstructions are characterised by acute onset, severe abdominal pain. Vascular impairment is a feature of complete obstructions and strangulation usually occurs, leading to clinical signs of tachycardia, tachypnoea, prolonged capillary refill time and congested mucous membranes. Borborygmi are often absent or significantly reduced. Large volumes of gastric reflux may be obtained and loops of distended small intestine may be palpated on rectal examination.

Partial obstructions are associated with more chronic clinical signs. Abdominal pain may be mild and intermittent, often co-inciding with feeding. Other clinical signs may include weight loss and reduced faecal output. Signs may occur over a period of weeks, during which time muscular hypertrophy of the intestine proximal to the partial obstruction occurs which is often recognisable at laparotomy.

Diagnosis

Diagnosis of intussusception in the horse may be difficult as abdominocentesis rarely reveals any abnormalities. This is due to the strangulated portion of gut being contained within the intussuscipiens. In the case of jejuno-jejunal intussusceptions, rectal examination may reveal a sausage-shaped, tubular structure in the mid abdomen of the horse. The presence of melaena is a significant finding and may raise clinical suspicion of intussusception. Abdominal ultrasonography may reveal a characteristic target or 'bulls-eye' lesion on transverse section. Peristalsis in the affected segment is reduced or absent. Oedema and thickening (>3mm) of the intestinal wall are often seen with a distended, fluid-filled region proximal to the intussusception.

Definitive diagnosis, however, is often based on findings at laparotomy.

See also Colic Diagnosis in Horses

Treatment

Treatment is surgical reduction of the affected region of intestine followed by resection and anastamosis. Although reduction alone without resection has been reported, this technique is not recommended due to the high possibility of recurrence.

See also Medical Treatment of Colic in Horses

Prognosis

The prognosis is good if surgery is performed before the intussusception has become irreducible. The prognosis is poorer if reduction is not possible due to the increased rate of post-operative complications including ileus, adhesions, peritonitis and endotoxaemia.

References

• Knottenbelt, D. C., Pascoe, R. R. (2003) Diseases and Disorders of the Horse Elsevier Health Sciences

• McIlwraith, C. W., Turner, Robertson, J. T. (1998) McIlwraith & Turner's Equine Surgery: advanced techniques Wiley-Blackwell

• Orsini, J. A., Divers, T. (2007) Equine Emergencies: Treatment and Procedures Elsevier Health Sciences

• Radostits, O. M., Arundel, J. H., Gay, C. C. (2000) Veterinary Medicine: A textbook of the diseases of cattle, sheep, pigs, goats and horses Elsevier Health Sciences

• White, N. A., Edwards, B (1999) Handbook of Equine Colic Butterworth Heinemann