Page 1382 - Equine Clinical Medicine, Surgery and Reproduction, 2nd Edition

The foal 1357

VetBooks.ir expansion of previously collapsed capillary beds. or defects in other portions of the urinary tract have
a poorer prognosis.
The peritoneal drainage catheter can be left in place
until the defect is corrected surgically. Abdominal
drainage will improve ventilation by decreasing DIARRHOEA
intra-abdominal pressure. Cardiovascular support
should be maintained, because although total body Definition/overview
water will be increased by the presence of urine Diarrhoea is one of the most common conditions
within the peritoneal space, the effective circulating encountered in foals. In one survey, up to 80% of foals
volume is still likely to be significantly decreased. under 6 months of age had one or more episodes of
Acid–base and electrolyte abnormalities should be diarrhoea. Diarrhoea is a clinical sign rather than an
corrected with intravenous fluid therapy (0.9% or actual disease. The severity can vary from a transient
0.45% saline with 5% dextrose can be used; potas- self-limiting episode in an otherwise healthy foal to a
sium-containing fluids should be avoided). In hyper- life-threatening condition as a result of the disease or
kalaemic animals, dextrose-containing fluids, such of secondary complications. Identification of the spe-
as 5% dextrose saline, are indicated (4–8 ml/kg/ cific aetiology in individual cases is difficult because
minute). Hyponatraemia should be corrected slowly. of the extensive list of causes and limited diagnostic
With severe and life-threatening hyperkalaemia (K methods available. Treatment is often supportive in
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>5.5 mmol/l [>5.5 mEq/l]), insulin (0.1–0.5 IU/kg s/c the physiological and non-infectious forms.
or i/v) or sodium bicarbonate (1–2 mEq/kg) may be
used alongside fluid therapy and abdominal drainage Aetiology/pathophysiology
to decrease serum potassium concentrations. These In the young foal, immature colonic function is
therapies facilitate the movement of potassium ions unable to compensate for small intestinal disease and
into cells. Calcium gluconate can be used as a tran- therefore many more causes of diarrhoea are associ-
sient cardioprotective medication to antagonise the ated with small intestinal disorders than are seen in
effects of K on cell membranes. Continuous ECG the adult. The list of possible causes in the foal is
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monitoring is required in cases of severe hyperka- extensive, but it can be split up on the basis of the
laemia because of the risk of bradycardia, cardiac pathophysiology of the individual diseases:
conduction abnormalities, arrhythmias and cardiac
arrest. Broad-spectrum antibiotics are indicated, but • Physiological: Many foals will have a bout of
nephrotoxic drugs such as aminoglycosides should mild and self-limiting diarrhoea at 7–10 days old
be used with caution in these foals. that may last for 1–7 days and is associated with
Once the foal is metabolically stable, surgical repair the initial stages of development of normal large
of the bladder should be performed without delay. bowel function. ‘Foal heat diarrhoea’ is so-called
Umbilical remnants may be surgically removed, and because of its association with this part of the
peritoneal lavage is often carried out prior to surgery mare’s reproductive cycle. It is not related to
to repair the defect. Laparoscopic repair has been milk changes but is associated with development
reported, but many clinicians still prefer a conven- towards normal function of the large colon
tional midline laparotomy approach. Some foals are and establishment of the natural microflora
managed postoperatively with an indwelling urinary of the colon and caecum by coprophagia and
catheter for a short period of time. Damage or prob- exploration of the environment by the foal.
lems elsewhere in the urinary tract are rare and sur- The diarrhoea is profuse and watery, but the foal
gical approaches are decided on a case-by-case basis. remains well and on suck.
• Dietary: Well-known causes include milk
Prognosis overload, inappropriate milk replacer feeding
In uncomplicated cases of bladder or urachal defects, to orphan foals, dietary indiscretion and
the prognosis for recovery is good, providing the lactose intolerance (see p. 818), which can be a
foal is stabilised prior to anaesthesia. Second surger- secondary complication of infectious enteritis
ies are occasionally required. Concomitant infection from rotavirus or Clostridium difficile infection.