Page 801 - Problem-Based Feline Medicine

35 – THE CONSTIPATED OR STRAINING CAT 793

Loss of autonomic control to the eye and heart result in to a normal position in a cat with dysautonomia,
dilated fixed pupils and a fixed heart rate. but will have no effect on a normal cat.
– This results from the phenomenon of denerva-
Tenesmus is attributable to constipation and/or
tion hypersensitivity in the dysautonomic cat,
dysuria.
causing an enhanced response to direct-acting
agents.
Clinical signs ● By contrast, topical physostigmine is an indirect-
acting parasympathomimetic agent, which acts by
Dysautonomia is primarily seen in young cats (< 3 years
inhibiting cholinesterase to prevent local degrada-
old).
tion of acetylcholine, causing rapid miosis in
Outbreaks in multicat households and single isolated a normal cat, but no response in a cat with
cases have been reported. dysautonomia.
Signs often develop acutely over 48 h, with nearly all Determination of plasma and urinary catecholamine
cats showing depression and anorexia. In some cats, concentrations may also be useful. Plasma epinephrine
signs develop over several weeks, and weight loss may and norepinephrine concentrations and urinary cate-
be evident. cholamine levels are reduced in cats with dysautono-
mia compared to normal cats.
Regurgitation associated with megaesophagus, vom-
iting, constipation, weakness and dry mucous mem-
branes of the mouth, nose and eye, are the most Differential diagnosis
commonly reported clinical signs.
The clinical features of classical feline dysautonomia
Pupils are dilated and fixed, but the cat is visual. make most other diseases unlikely.
There is protrusion of the third eyelids in more than
Atypical cats may present with constipation or obstipa-
90% of affected cats, and the eyes appear dry.
tion as the major sign. Careful physical examination,
Braycardia of 90–120 beats per minute occurs in and an index of suspicion for dysautonomia are
about 60% of cats. required to make a diagnosis in these cats.
Loss of anal tone and fecal incontinence may be evident.
Treatment
Dysuria and a distended bladder are less common
signs. Urinary incontinence may also occur. Treatment is supportive but palliative in most
instances. Approximately 20–40% recover with sup-
Occasionally constipation or obstipation is the major
portive therapy. Recovery is over 2–12 months, and
presenting sign, and the other signs are less obvious.
may not be complete.
Diagnosis Correct dehydration if present.
A presumptive diagnosis is usually made based on the Prolonged nutritional support should be provided via
characteristic clinical presentation. parenteral or enteral means if there is persistent vomit-
ing or regurgitation.
Survey and/or contrast radiography demonstrate
megaesophagus, delayed gastrointestinal transit Parasympathomimetic drugs may be administered to
and/or bladder distention. improve oronasal secretion, and treat the ocular mani-
festations of the condition, especially decreased
Confirmation of abnormal autonomic function tests
lacrimation.
may be pursued if indicated. Ocular (pupillary)
● Pilocarpine drops (0.25–1% solution 1 drop q
response tests to 0.1% pilocarpine and 0.25%
6–8 h).
physostigmine may be performed.
● Physostigmine drops (0.5% 1 drop q 12 h).
● Pilocarpine is a direct-acting parasympath-
omimetic agent, which when applied topically will Metoclopramide (Reglan, 0.2–0.4 mg/kg PO or SC q
result in miosis and retraction of the third eyelid 8 h) enhances gastrointestinal motility. The aim is