Page 812 - Equine Clinical Medicine, Surgery and Reproduction, 2nd Edition

Gastrointestinal system: 4.2 The lower gastrointestinal tr act 787

VetBooks.ir endotoxaemia, pain and general anaesthesia can also very important to characterise intestinal size, wall
thickness and motility.
have a deleterious effect on motility. Vascular or
obstructive intestinal injuries such as torsion, entrap-
ment and strangulation will cause an obstructive ileus. Management
The extrinsic nervous system and local enteric Supportive therapy, including i/v fluid therapy, with-
nervous system control GI motility. In the extrin- holding of feed and water and frequent gastric decom-
sic nervous system, intestinal motility is stimulated pression is critical. This may be achieved by passage
by parasympathetic activity (acetylcholine), while of a NG tube or by the use of an indwelling NG
sympathetic stimulation (norepinephrine) has an tube. Fluid rates should be calculated based on the
inhibitory effect. An imbalance between these two initial fluid deficit, maintenance requirements and
components results in ileus. ongoing losses. Urine output is an effective and easy
means of measuring ongoing hydration. Electrolyte
Clinical presentation imbalances should also be corrected because of the
Ileus is often secondary and clinical findings of negative effect of hypokalaemia, hypomagnesaemia
the primary disease may predominate. In general, and hypocalcaemia on motility.
adynamic ileus is associated with depression, mild Analgesia is often required. Drugs with inhibitory
to severe abdominal pain, anorexia and decreased effects on intestinal motility should be avoided if
faecal output. Borborygmi are usually absent or possible, but they are sometimes necessary. Multiple
reduced. Heart rate and respiratory rate are often prokinetic drugs have been used, but none have
elevated. Signs associated with hypovolaemia can proven completely satisfactory due to undesirable
also be present due to intestinal sequestration of flu- side-effects or an inconsistent response (Table 4.3).
ids. Accumulation of fluid in the stomach because In cases of large-colon stasis, enhanced motility
of a lack of progressive motility can result in severe may result when laxatives are administered by NG
pain or gastric rupture. In cases of obstructive ileus, tube via the gastrocolic reflex. Historical recom-
the clinical signs are usually more severe and endo- mendations include mineral oil (10 ml/kg), sodium
toxaemia can be present. sulphate (0.15–0.5 g/kg) or magnesium sulphate
(0.5–1.0 g/kg) in 4 litres of warm water, or dioctyl
Differential diagnosis sodium succinate (DSS) (10–30 mg/kg of a 10% solu-
Adynamic ileus should be differentiated from obstruc- tion). More recently the frequent (q1-2 h) adminis-
tive diseases that require surgical intervention. tration of 10–20 ml/kg balanced electrolyte solution
via NG tube has been shown to be superior to tradi-
Diagnosis tional laxative therapy.
Distended small intestinal loops are often palpable If ileus persists or an underlying obstructive cause
p/r. In cases of ileus involving the large intestine, is suspected, an exploratory laparotomy should be
caecal or large-intestinal distension can be pal- performed to decompress the intestine or correct the
pated. Passage of a NG tube is a vital diagnostic primary problem.
and therapeutic procedure. The volume of reflux
should be recorded. The PCV is often increased Prognosis
and total protein levels may be increased or In cases of obstructive ileus, the prognosis will
decreased depending on the degree of intestinal depend on the underlying cause. In the case of ady-
protein loss and haemoconcentration. Leucopenia namic ileus, the prognosis is good to fair.
may be present if ileus is associated with an acute
inflammatory response. Sequestration of fluid INTESTINAL STRICTURE
in the intestines may result in hypokalaemia,
hypocalcaemia, hypochloraemia and hyponatrae- Definition/overview
mia. Peritoneal fluid is usually normal in non- A stricture is a reduction of the intestinal lumen that
surgical cases. Ultrasonographic examination is typically occurs following local trauma.