Rectal Prolapse - Horse

Description

Rectal prolapse in the horse is associated with conditions causing tenesmus (straining). These may include dystocia, constipation, neoplasia, foreign body obstruction, urethral obstruction or diarrhoea. Occasionally there is no apparent underlying cause.

Rectal prolapse is classified according to the type of tissue involved. Type I (or 'incomplete' prolapse) involves the rectal mucosa and submucosa only, appearing as a large 'doughnut' shaped soft tissue swelling at the rectum. Type II ('complete' prolapse) involves the entire rectal wall. Type III involves complete prolapse of the rectum in addition to intussusception of the peritoneal rectum. Complete intussuseption of the peritoneal rectum beyond the anus occurs with type IV rectal prolapse.

Signalment

Mares are more commonly affected than geldings or stallions.

Diagnosis

A cylindrical soft-tissue mass protruding from the rectum is usually diagnostic for rectal prolapse. In the dystocic mare, a full vaginal and rectal examination should be carried out in order to rule out the possibility of tears. Other diagnostic tests to investigate the underlying cause of the prolapse may include endoscopy of the bladder and lower urinary tract, rectal biopsy and rectal endoscopy.

Treatment

Treatment should be aimed at reducing the prolapse as well as identifying and correcting the underlying cause of tenesmus. Affected horses should be prevented from becoming recumbent before the prolapse has been replaced.

Treatment depends on the type of prolapse. A simple prolapse of the rectum or rectal mucosa may be easily replaced providing minimal soft tissue trauma, contamination or dessication has occurred. In order to reduce any oedema, glycerin or dextrose combined with petroleum jelly may be applied topically. The prolapse may be replaced under epidural anaesthesia and a purse string suture placed in the anus. If the prolapse cannot be manually reduced, surgical amputation or resection of exposed tissue may be required. In the case of Type III and Type IV rectal prolapse, coeliotomy of the intussuscepted segment must be performed.

It is important to provide faecal softeners following reduction of a prolapse to prevent straining and reduce the possibility of recurrence. Other complications following reduction include wound breakdown, infection and uterine or bladder prolapse (in mares).

Prognosis

The prognosis varies depending on the underlyig cause but is generally good for Type I and Type II prolapse, and guarded for Type III and Type IV.

References

• Lavoie, J. P., Hinchcliff, J. W. (2009) Blackwell's Five Minute Veterinary Consult: Equine John Wiley and Sons
• Mair, T. S., Divers, T. J., Ducharme, N. G. (2002) Manual of Equine Gastroenterology Elsevier Health Sciences
• Orsini, J. A., Divers, T. (2007) Equine Emergencies: Treatment and Procedures Elsevier Health Sciences