Sand Impaction - Horse

See Colic Diagnosis in Horses

Medical Treatment of Colic in Horses

Description

Impaction of the large colon is seen in horses with limited access to drinking water or those grazing bare pastures. Horses fed on a low-roughage diet are more prone to developing the condition. The ingested sand may act as an inflammatory stimulus, causing a foreign body enteritis. 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.

Clinical signs

Ingestion of sand without impaction may lead to clinical signs pertaining to a physical colitis due to the abrasive nature of sand. These may include diarrhoea, 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 is made via rectal palpation or transrectal ultrasonography with identification of sand in the colon. An impaction may also be detected per rectum, but in many cases the impacted segment is located in the cranial gastrointestinal tract and therefore out of reach. Transrectal ultrasonography may assist in identifying the presence of sand. 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.

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. Psyllium is administered directly into the stomach via a nasogastric tube and the sand becomes incorporated into the laxative. Some authors however have described no benefical effects of Psyllium and adovate restriction to access to sand as the main component of treatment. This treament is continued for up to a week until all sand is fully removed from the colon.

If the impaction is large or non-responsive to medical treatment, surgery may be indicated.

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.

Prognosis

For cases that are not resolved by conservative treatment, the prognosis is good if surgery is performed early. The overall mortalitiy 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