Page 902 - Equine Clinical Medicine, Surgery and Reproduction, 2nd Edition

Liver disease 877

VetBooks.ir to a subclinical hepatopathy. In reality, this binary 5.6
distinction of hepatic functional failure versus sub-
clinical liver disease may not be so clear cut. Further
clinical signs may be seen in cases of hepatic insuf-
ficiency that do not have an obvious basis in loss of
known specific liver functions such as colic, diar-
rhoea and constipation. Additionally, horses are also
seen where clinical signs are present in the absence
of apparent hepatic failure. Commonly such signs
may be non-specific and include subdued appetite
and demeanour or loss of performance or enthusi-
asm for exercise. However, photodermatitis cases are
also seen in association with liver disease where other 5.7
diagnostic data do not suggest hepatic insufficiency.
Where non-specific clinical signs are observed in
horses with liver disease, but no apparent functional
failure is present, it should also be considered that the
liver disease may be coincidental, and that the clinical
signs might actually be attributable to another non-
hepatic disease. Experience indicates that subclinical
liver disease is remarkably common in apparently
healthy equids, so such a coincidence is not unlikely.
Hepatic encephalopathy (HE) results from hepatic
insufficiency or portosystemic bypass and is one of
the most common causes of clinical signs of cerebral
disease in the horse. It may present with obtunda-
tion, behavioural changes, yawning (Fig. 5.6),
disorientation, compulsive walking, ataxia, circling, 5.8
blindness, head-pressing, ptyalism (Fig. 5.7), sei-
zure and coma. Cases may be seen after becoming
entangled in fencing or hedges, for example, and are
easily misdiagnosed as demonstrating neurological
signs due to head trauma unless HE is considered.
Other clinical signs of HE also recognised that may
be related to peripheral nerve dysfunction are foot
stamping, pruritus, dysphagia, gastric impaction and
bilateral laryngeal paralysis (Fig. 5.8). The latter is
sometimes seen as a sole presenting sign of hepatic
insufficiency with acute-onset respiratory distress,
inspiratory dyspnoea and loud stridor and is again
easily misunderstood unless the clinician is aware of
the association with HE. Respiratory obstruction
can be relieved by placing a temporary tracheostomy
tube while medical treatment is implemented to
control HE (see later for treatment options). Horses Figs. 5.6–5.8 Images demonstrating signs of hepatic
with signs of HE have a poorer prognosis than those encephalopathy including: (5.6) somnolence and
with liver disease without HE although attempted head-pressing; (5.7) ptyalism; (5.8) respiratory distress
treatment of the condition is justifiable. associated with bilateral laryngeal paralysis.