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WSV18-0224
TIPS FROM THE EXPERTS FOR THE MANAGEMENT OF...
HIGH LIVER ENZYMES
N. Prakash1
1Mount Pleasant Veterinary Centre, Small Animal Medicine, Singapore, Singapore
TIPS FROM THE EXPERTS FOR THE APPROACH AND MANAGEMENT OF
HIGH LIVER ENZYMES
Nathalee Prakash BSc BVMS (Hons) FANZCVS (Canine Medicine)
Mount Pleasant Veterinary Centre samedicine@mountpleasant.com.sg Liver Enzymes vs Liver Function Tests
Liver test abnormalities can be categorised loosely into markers of hepatocellular injury, cholestasis, or impaired liver function.
Transaminases ALT and AST
ALT is a cytoplasmic enzyme of hepatocytes that is more specific than AST. ALT has a half-life of 6 hours in a cat and 48-60 hours in a dog, making it a good indicator
of continued liver injury.1AST is a mitochondrial-bound enzyme found in high concentrations in hepatocytes. Consequently, its increase indicates cell death. However, AST is also found in myocytes and red blood cells. The half-life is 77 minutes in a cat and 22 hours in a dog.1
Indicators of Cholestasis
ALKP and GGT typically increase with cholestatic disease or drug induction. Cholestasis increases the surface tension of the bile canaliculi and ductules, inducing enzyme production. ALKP has a half-life of 66- 70 hours in dogs and 6 hours in cats.1Apart from being hepatobiliary in origin, increased bone isoenzyme may occur in young animals or those with lytic or neoplastic bone lesions. In dogs, ALKP increase is also seen with endogenous or exogenous corticosteroids and anti- epileptic drugs (AEDs), whereas GGT does not increase with bone activity and AEDs.
Liver Function
Liver failure can manifest as decreased synthetic capacity, decreased uptake and excretion of bile acids, and decreased conversion of ammonia to urea. For example, laboratory evidence of decreased synthetic capacity can occur when 70-75% of the hepatic functional mass is lost. Hepatic dysfunction may manifest as decreased albumin, glucose, cholesterol and BUN. Production of coagulation factors, fibrinogen, as well as coagulation inhibitors (e.g. protein C and anti-thrombin) are also affected.
43RD WORLD SMALL ANIMAL VETERINARY ASSOCIATION CONGRESS AND 9TH FASAVA CONGRESS
25-28 September, 2018 | Singapore
use of the canine assay is considered reasonable.
A low total T4 and high TSH should be interpreted
as indicating hypothyroidism and managed by decreasing the antithyroid drug dosage or implementing L-thyroxine supplementation. Reference interval total
T4 concentrations with high TSH may also represent reduced thyroid function and should be carefully monitored particularly if azotaemic.
References
1. Vaske HH, Schermerhorn T, Grauer GF. Effects of feline hyperthyroidism on kidney function: a review. J Fel Med Surg; 2015; do1: 10.1177/1098612X15575385.
2. Williams TL, Peak KJ, Brodbelt D et al. Survival and the development of azotemia after treatment of hyperthyroid cats. J Vet Intern Med; 2010; 24; 863- 869.
3. Peterson ME, Guterl JN, Nichols R, et al. Evaluation of serum thyroid-stimulating hormone concentrations as a diagnostic test fro hyperthyroidism in cats. J Vet Inter Med; 2015; 29; 1327-1334.
4. Williams TL, Elliott J, Syme HM Association of iatrogenic hypothyroidism with azotemia and reduced survival in cats treated for hyperthyroidism. J Vet Intern Med 2010; 24; 1086-1092.
5. Boretti FS, Sieber-Ruckstuhl NS, Schafer S et al. Duration of T4 suppression in hyperthyroid cats treated once and twice daily with transdermal methimazole. J Vet Intern Med; 2013; 27, 377-381.
6. Daminet S, Kooistra HS, Fracassi F et al. Best practice for the pharmacological management of hyperthyroid cats with antithyroid drugs. J Small Anim Pract; 2014; 55, 4-13.
7. Boretti FS, Sieber-Ruckstuhl NS, Schafer S, et al. Transdermal application of methimazole in hyperthyroid cats: a long-term follow-up study. J Fel Med Surg; 2013; 16; 491-498.
8. Peterson ME, Broome MR, Rishniw M. Prevalence and degree of thyroid pathology in hyperthyroid cats increases with disease duration: a cross-sectional analysis of 2096 cats referred for radioiodine therapy. J Fel Med Surg; 2015; doi: 10.1177/1098612X15572416.
9. Hui TY, Bruyette DS, Moore GE, Scott-Moncrieff JC. Effect of feeding an iodine- restricted diet in cats with spontaneous hyperthyroidism. J Vet Intern Med; 2015; 29, 1063-1068.
10. Peterson ME, Nichols R, Rishniw M Serum thyroxine and thyroid-stimulating hormone concentration in hyperthyroid cats that develop azotaemia after
radioactive iodine therapy. J Small Anim Pract; 2017; doi:10.1111/jsap.12695































































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