Page 872 - Equine Clinical Medicine, Surgery and Reproduction, 2nd Edition

Gastrointestinal system: 4.2 The lower gastrointestinal tr act 847

VetBooks.ir Management is covered under the specific obstruction. Caecal
tympany is often present concurrently.
In the absence of a specific diagnosis, a variety of
treatments can be tried. Diet change may be useful
and nutritional analysis is recommended. Generalised Clinical presentation
dietary recommendations cannot be made because Signs of abdominal pain (rolling, pawing, flank-
of the variability in response but a diet consisting watching, stretching, recumbency, anorexia) will
of mainly, or exclusively, hay or pasture grass can vary with the degree of abdominal distension. Pain
be beneficial; however, some horses will respond to can range from mild and intermittent to continuous
provision of a hay-free diet. Moxidectin (0.4 mg/ and severe. Heart rate is usually elevated consistent
kg p/o once) is often prescribed. Metronidazole (25 with the degree of pain. Gross abdominal disten-
mg/kg p/o q8–12 h for 5 days) is also often used but sion may be present. Distension is usually bilateral
is questionable. Probiotics are widely used, but no (as opposed to caecal tympany) and marked disten-
beneficial effect has yet been demonstrated. Yogurt sion may result in tachypnoea via pressure on the
is unlikely to be effective because it contains low diaphragm. Mucous membranes are usually normal
viable bacteria numbers and does not contain organ- unless severe distension is present. Borborygmi may
isms with any known benefit in horses. Treatment be normal, increased or decreased. High-pitched
for sand enteropathy may be attempted in certain tympanic sounds may be heard during simultaneous
areas. Corticosteroids such as dexamethasone (5–10 auscultation and percussion of the abdomen.
mg/450 kg i/m q24 h for 21 days, then tapering) or
prednisolone (1 mg/kg p/o q24 h for 3 weeks) are Differential diagnosis
often used after other treatments have failed. A variety of signs of colic must be considered, par-
ticularly spasmodic colic, large-colon impaction and
Prognosis large-colon displacement.
In general, the prognosis is fair if diarrhoea is
accompanied by other clinical abnormalities such as Diagnosis
weight loss or hypoproteinaemia. If diarrhoea is the The most important factor in the diagnosis of
only complaint, then the prognosis for survival and colonic tympany is ruling out the presence of sur-
normal function is often good, despite the fact that gical disorders such as large-colon volvulus or dis-
diarrhoea may persist. placement. Distension of the large colon may be
palpable p/r. A thorough examination is required to
COLONIC TYMPANY (GAS COLIC) try to identify a lesion that may be the cause of the
distension. A NG tube must be passed. Gaseous dis-
Definition/overview tension of the stomach may be present concurrently.
Intestinal tympany, also known as gas colic, is a Ultrasonographic examination of the abdomen is
common cause of colic. unremarkable. Peritoneal fluid analysis and haema-
tology should be unremarkable.
Aetiology/pathophysiology
A variety of risk factors have been suggested includ- Management
ing diet change, feeding of highly fermentable Analgesic administration is usually required. Drugs
substrates (grain, lush grass, wilted grass), rapid affecting intestinal motility should be used judi-
eating, electrolyte abnormalities and dental abnor- ciously and only when required. Mineral oil (4 litres
malities. Excessive production of intestinal gas via NG tube) may coat fermentable substrates, but
and/or alterations in colonic motility may result in its efficacy is unclear. Feed should be withheld.
colonic tympany if the rate of gas production exceeds Frequent walking may be useful to simulate intesti-
the rate of elimination. As the intestine distends nal motility. Short periods of more intense exercise
with gas, signs of pain may develop. Colonic tym- such as trotting on a lunge line may also be useful,
pany that develops secondary to obstructive lesions particularly in more severe cases.