Vascular liver diseases in cats
7.6.2.1 Congenital portosystemic shunt
In contrast to dogs, which are affected by multiple vascular liver diseases, the only vascular anomaly of significance in cats is congenital portosystemic vascular anomaly, also known as congenital portosystemic shunt (CPSS).87,91
Cats are affected by a wide variety of shunts, which are usually localized outside the hepatic parenchyma.
Such extrahepatic shunts can be located between the liver and the diaphragm, but also as far back as the pelvic canal. However, as in dogs, CPSS can sometimes also be intrahepatic.87 There is no breed or sex predisposition for CPSS in cats and the incidence of CPSS is much lower in cats than it is in dogs. In cats, it is not only important to monitor the serum blood glucose concentration during and following surgical correction of the shunts, but also the clinician should be aware of the risk of an insufficient intake of essential amino acids. Supplementation of these amino acids may be administered intravenously or orally. Congenital shunts are the only condition in cats that is associated with microhepatica.A diagnosis of CPSS in cats can be confirmed by ultrasonography, transcolonic or splenic portal scintigraphy, or contrast portal venography. The liver size in affected cats is usually smaller than normal. A hepatic biopsy specimen should always be obtained to ensure that the hepatic histological changes that are characteristic of CPSS are present: lobular hepatocellular atrophy, inconspicuous portal vein tributaries, arteriolar duplication, and, occasionally, mild lipidosis and vacuolar changes. In Persian cats, the co-existence of cystic kidney and liver disease that is associated with hepatic fibrosis is a contraindication for surgery.
Treatment
The definitive treatment for CPSS in cats is the surgical ligation of the anomalous vessel, assuming there is adequate intra- hepatic portal venous vasculature to accept the redirected blood flow.
This surgical procedure is best performed at referral centers or veterinary colleges. Older cats (>5 years of age) or cats with pre-existing neurological signs may be at greater risk of a poor outcome following surgical treatment of CPSS. The author recommends to treat cats that undergo surgery for CPSS symptomatically (i.e., diet, lactulose) before surgery, and to continue treatment for 1 month after surgery.The success rate of surgery for CPSS in cats is lower than that in dogs and only 40-50% of cats recover. Cerebrocortical necrosis is a relatively frequent postoperative complication in cats and causes irreversible brain damage.
Symptoms
Obvious behavioral and neurological abnormalities (e. g., dementia, ataxia) are commonly seen in cats with CPSS. Also, intermittent ptyalism is a much more frequent manifestation of HE in cats than it is in dogs.
Diagnosis
It is the author’s opinion that, as in dogs, the most accurate modality to diagnose portosystemic shunting is by measuring the plasma ammonia concentration. In cases where a single plasma ammonia concentration does not provide a definitive answer, an ammonia tolerance test may be diagnostic. Serum bile acids concentrations may also be indicative of a portosystemic shunt, but they are nonspecific. As in dogs with PSS, hypoalbuminemia and ammonium biurate crystalluria may also be present in affected cats.
7.6.3