Sand Impaction - Horse

unfinished See Colic Diagnosis in Horses

Medical Treatment of Colic in Horses

Description

Sand impaction of the large colon is seen in horses with limited access to drinking water or those grazing bare pastures. Occasionally sand may be consumed when included with hay. The ingested sand may act as an inflammatory stimulus leading to a foreign body enteritis, commonly known as 'sand colic'. Alternatively it may accumulate and form a sediment within the right dorsal colon, pelvic flexure and transverse colon leading to an impaction.

Sand impactions are particularly common in dry sandy regions of the world and are far less common in the UK and rest of Europe. Although all horses may be affected, indiscriminate feeders and young horses that may consume sand voluntarily are more commonly affected. Horses fed on low-roughage diets are more prone to developing the condition.

Clinical signs

Ingestion of sand without impaction may lead to clinical signs associated with a physical colitis due the abrasive nature of sand. These include diarrhoea and signs of endotoxaemia, such as congested mucous membranes and a prolonged capillary refill time. If sufficient sand has been ingested to cause an impaction, the clinical signs are generally dependent on the anatomical site affected. Horses affected by a pelvic flexure impaction often present with signs of mild abdominal pain and generally respond well to conservative treatment. Impaction of the transverse colon is often associated with more severe abdominal pain due to the build up of gas in the the colon proximal to the obstruction.

Diagnosis

Affected horses may have a history of living in a sandy environment, grazing in dry weather or a reduction in water intake. Auscultation of the abdomen may reveal gritty-sounding 'rubs' heard as the sand moves through the colon. Definitive diagnosis of an impaction is made via rectal palpation or transrectal ultrasonography. In many cases however the impacted segment is located in the cranial gastrointestinal tract and is therefore out of reach. Sand also may be seen in the faeces by mixing faecal material with water in a plastic rectal examination sleeve and allowing the sand to fall to the bottom. If performed, abdominocentesis should be carried out with extreme caution in order to avoid inadvertent laceration of the sand-impacted colon. Abdominal radiography may be useful in assessing the volume and location of sand impactions in foals, minature horses and small ponies.

Treatment

Bulk laxatives such as Psyllium are widely used to assist in the movement of sand. A mixture of Psyllium mucilloid and water is administered directly into the stomach via a nasogastric tube. This treatment is continued for up to a week until all sand is fully removed from the colon. Intravenous fluid therapy may be beneficial in increasing the fluid content of the impacted ingesta.

If the impaction is large or non-responsive to medical treatment or analgesia, surgery may be indicated. A ventral midline exploratory coeliotomy is peformed and the sand is removed via a pelvic flexure enterotomy. Post-operative complications such as ileus, peritonitis and endotoxaemia are relatively common due to damage to the colonic wall.

Prevention of recurrence is important; horses should be fed from buckets to prevent further ingestion of sand. Water should be freely available and plentiful. Horses should not be allowed access to over-grazed pasture. High fibre diets such as hay are recommended. Psyllium may be administered every four to twelve months to horses that are chronically affected.

Prognosis

For cases that are not resolved by conservative treatment, the prognosis is good if surgery is performed early and the colon has not become necrotic or ruptured. The overall mortality rate for horses requiring surgery is reported to be 40%.

References

Hammock, P. D., Freeman, D. E., Baker, G. J. (1998) Failure of Psyllium Mucilloid to Facilitate the Evacuation of Sand from the Equine Large Intestine AAEP Proceedings 9 Vol. 44 pp 246-247

Mair, T. S., Divers, T. J., Ducharme, N. G. (2002) Manual of Equine Gastroenterology 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