Rectal Tear - Horse

Description

Rectal tears are serious injuries in the horse, most commonly occurring as a result of rectal examination by a veterinarian. Other less common causes of tears include dystocia, ruptured haematomas, spinal fractures, strictures and thromboembolism. Most rectal tears are located dorsally, 25-30 cm from the anus at the junction of the rectum and the small colon. Rectal tears may occur in horses of all ages although nervous or young horses are more often affected. Arabaians and small horses are also more prone to developing tears.

Rectal tears are classified according to the layers of the bowel wall.

• Grade 1) Involves the mucosa only.
• Grade 2) Mucosal and submucosal tears
• Grade 3) Tears involving the muscularis. Only the serosa is intact
• Grade 4) Complete tear with leakage of faecal material into the abdomen

Clinical signs

Many rectal tears occur unknown to the examiner. The first indication that a tear has occurred may be the presence of fresh blood on the rectal sleeve following rectal examination. The veterinarian may be aware of a sudden release in pressure or increase in space when performing rectal examination. If the tear is complete, abdominal viscera may be easily palpable. Other clinical signs indicative of a rectal tear may include passage of haemorrhagic faeces, straining to defecate and signs of colic.

Diagnosis

If a rectal tear is suspected, it is important to establish its extent as this dictates the treatment required and the prognosis for recovery. The horse should be sedated before further examination is carried out and an epidural should be performed in order to prevent straining. Careful rectal examination and endoscopy should be performed to locate and assess the tear in order to select appropriate management and treatment.

Treatment

Grade 1 and 2 tears are best managed conservatively with a combination of non-steroidal anti-inflammatory drugs, broad-spectrum antibiotics and laxatives such as mineral oil. A moist diet such as bran mash or grass should be provided in order to aid defecation. The horse should be closely monitored for signs of colic, haematochezia, dyschezia, pyrexia and tenesmus. Repeated rectal examination should be avoided unless unavoidable. Tears less that two to three centimetres in length usually heal without causing further problems and rarely require treatment.

Grade 3 and 4 tears are acute, life-threatening emergencies and should be referred to a surgical facility. Before transportation it is essential that appropriate emergency care is provided and measures are taken to prevent faecal contamination. Epidural anaesthesia should be performed using either xyalzine alone or xylazine in combination with lidocaine or mepivicaine. The rectum should be packed with an antiseptic tampon positioned cranially to the tear and extending to the anus. A length of stocking filled with betadine-soaked cotton has been recommended for this. Following this a purse-string suture should be placed in the rectum to prevent expulsion of the tampon. Broad-spectrum antibiotics, flunixin meglumine and appropriate tetanus prophylaxis should also be administered.

At the referral facility, abdominocentesis is performed to check for peritonitis. A number of surgical techniques have been described for the repair of Grade 3 and Grade 4 tears. These include suturing the tear closed via a rectal or ventral midline approach, or the use of a faecal diversion technique such as temporary colostomy to eliminate the passage of faeces throught the rectum. Surgical repair of rectal tears is associated with a high failure rate and consideration to the finance and the animal's welfare should be given before surgery is carried out.

Prognosis

The prognosis for rectal tears depends on the size, location and grade of the tear and the length of time between occurrence and treatment. Grade 1 and Grade 2 tears generally have a good prognosis and usually heal without complication. Grade 3 and Grade 4 tears are associated with a poor prognosis. If peritonitis is present the prognosis is grave and euthanasia is usually required.

References

• England, G. C. W. (2005) Fertility and Obsetrics in the Horse Wiley-Blackwell'
• Knottenbelt, D. C., Pascoe, R. R. (2003) Diseases and Disorders of the Horse Elsevier Health Sciences
• Robinson, N. E., Sprayberry, K. A. (2009) Current Therapy in Equine Medicine Elsevier Health Sciences
• Rose, R. J., Hodgson, D. R. (2000) Manual of Equine Practice Elsevier Health Sciences