Page 370 - Problem-Based Feline Medicine

362 PART 6 CAT WITH WEIGHT LOSS OR CHRONIC ILLNESS

Classical signs—Cont’d Copper- or golden-colored irises have been noted in
some cats with portosystemic shunts.
● Neurological signs – hypersalivation,
seizures, ataxia, blindness and behavioral Heart murmurs have also been noted in some affected cats.
changes. Ascites and signs of primary hepatic disease may be
● Inappetence, vomiting or diarrhea. seen in cats with acquired portosystemic shunts.

See main references on page 588 for details (The Cat
With Salivation).
Diagnosis
Clinical signs Routine hematology and biochemistry may be unre-
markable in cats with congenital portosystemic shunts
Portosystemic shunts are vascular communications however:
between the portal and systemic venous circulation, ● Routine hematology may reveal a mild non-regener-
and may be a congenital anomaly or acquired. ative, microcytic anemia often with poikilocytosis.
● Congenital portosystemic shunts in cats are usu- ● Hypoglycemia, hypoalbuminemia, hypocholes-
ally single extrahepatic shunts resulting from terolemia and decreased blood urea concentra-
developmental anomalies of the vitelline system. tions may indicate hepatic dysfunction.
– Persian and Himalayan cats are predisposed.
Pre- and post-prandial serum bile acids should be
– A predilection for male cats has been suggested,
assessed.
and such cats are often crypt-orchid.
● Pre-prandial bile acid concentrations may be nor-
– Cats with congenital shunts will usually show
mal or elevated.
clinical signs by 6 months of age, however a
● Post-prandial bile acids are typically elevated,
congenital portosytemic shunt should not be
frequently exceeding 100 μmol/L (39.2 mg/L).
excluded on the basis of age alone.
● Multiple extrahepatic acquired portosystemic Hyperammonemia, particularly post prandial is com-
shunts are formed secondary to portal hyperten- monly present.
sion, and are extremely uncommon in the cat.
Abdominal radiographs may demonstrate microhep-
– Acquired shunts usually occur in cats with
atica, but in many cats hepatic size is normal.
chronic, severe, diffuse hepatic disease.
Ammonium biurate crystals may be present on urine
Signs are often vague or non-specific and episodic.
sediment examination.
Cats with congenital shunts may show stunting ● Ammonium urate calculi are often radiolucent.
(smaller than littermates) or weight loss.
Portosystemic shunts may be identified and local-
Clinical signs of hepatic encephalopathy predomi- ized on abdominal ultrasound.
nate in cats with portosystemic shunts.
Other techniques may be required to definitively
● Vague anorexia, depression and weakness.
demonstrate the presence of shunting vessels.
● Ataxia, behavioral changes (bizarre and aggressive
● Transcolonic portal scintigraphy is a non-invasive
behavior), aimless pacing, blindness and seizures
technique but requires specialist equipment.
may occur.
– It may produce false-negative results when the
● Hypersalivation, often profuse, is also common.
shunt connects the gastric vein to the caudal vena
There are often intermittent episodes of vomiting, diar- cava, a common type of shunt in the cat.
rhea and inappetence with normal periods between. ● Venous portography, although requiring sur-
gery, is the definitive method for identifying
Lower urinary tract signs are present in cats with con-
shunts.
current urate urolithiasis.