Page 879 - Equine Clinical Medicine, Surgery and Reproduction, 2nd Edition

854 CHAPTER 4

VetBooks.ir hypertriglyceridaemia. Analgesics will usually be used. A simple, cheap, balanced electrolyte solu-
tion can be made with 45 ml NaCl and 15 ml KCl
required.
Treatment via NG tube may be useful in horses with-
out gastric reflux. Mineral oil (4 litres) has traditionally (30 ml table salt and 30 ml ‘Lite’ salt) per 8 litres of
water. Fluid administration should be stopped until
been used; however, its efficacy has not been proven. the horse is re-evaluated if signs of colic progress or
Mineral oil can pass around dense impactions without if gastric reflux develops. Intravenous fluid therapy
any beneficial effect and is probably more useful in mild may be required for more severe cases, or those that
impactions. DSS can also be administered orally, but a are refractory to oral therapy, but it is less effective
beneficial effect has not been demonstrated. Repeated at resolving large-colon impactions than repeated
administration of DSS should be avoided because it can enteral fluid administration.
be irritating, and toxicity can develop. Most impactions will resolve with medical treat-
Osmotic cathartics can be more useful with mag- ment, but very large impactions that do not respond
nesium sulphate (1 g/kg q24 h) most commonly used. to medical treatment, or cases with severe intractable
It may be wise not to use high doses of cathartics pain, may require surgical intervention (Fig. 4.171).
when very large, firm and potentially obstructive Rupture of the colon during exteriorisation is a risk
impactions are present because of the potential for of surgery because the intestinal wall can be thin and
the development of marked colonic distension. In friable.
these cases, it might be preferable to attempt to Following resolution of the impaction, it is
soften the impaction with fluid therapy prior to important that feeding be reintroduced gradually.
administration of cathartics. Small volumes of hay, hay cube slurries, grass or
Administration of water via a NG tube is cost- bran mashes should be used initially. Small volumes
effective and can be used successfully. With proper should be offered every few hours, with volume
observation, and having first checked that it is posi- increasing over time so that a normal hay or grass
tioned correctly, a NG tube can be left in place and ration is offered by 24–48 hours. The potential for
water (8 litres up to q30 min–2 h) can be adminis- underlying disease and risk factors for impaction,
tered. Excessive quantities of water (>30 litres per including management and dental disease, should be
day) have been associated with hyponatraemia and evaluated to help prevent recurrence.
accordingly balanced electrolyte solution should be
Prognosis
In general, the prognosis is very good, but worse if
4.171 surgery is required. It is suspected that severe and/
or long-standing impactions may damage stretch
receptors in the intestinal wall, predisposing to
recurrence. Rupture of the large colon during exte-
riorisation is a concern if surgical correction is
needed. Large-colon rupture is invariably fatal.

SAND IMPACTION

Definition/overview
Accumulation of large volumes of sand in the large
colon is a common cause of colic in some geographic
areas.

Aetiology/pathophysiology
Sand may be ingested while grazing on sandy soil,
Fig. 4.171 Pelvic flexure enterotomy. or from ingestion of sand in sandy paddocks, arenas