ALT Elevation in Healthy Dogs

In the Literature

Adams J. Long-term clinical outcomes of healthy dogs with increased alanine aminotransferase. J Small Anim Pract. 2024;65(12):857-866. doi:10.1111/jsap.13777

The Research …

Elevated ALT may be documented during wellness screening. ALT is mainly located in canine hepatocytes, and elevation can indicate hepatocellular disease; however, this enzyme can also be found in smaller amounts in other organs, may be elevated due to extrahepatic conditions, can fluctuate, and does not indicate reversibility of hepatocellular damage, making ALT a nonspecific marker for primary hepatic disease.^1,2

This retrospective study reviewed records of clinically healthy dogs of various ages and breeds to help define an ALT reference interval that warrants more extensive diagnostics in clinically healthy dogs, as well as to longitudinally follow clinical health and ALT after initial elevation on wellness screening. A total of 315 dogs underwent blood tests during the study, and 125 were used to establish the reference interval for the laboratory used in the study.

Of the 315 dogs, 19 had elevated ALT on ≥1 test during the study and underwent ≥1 follow-up test when clinically healthy. A majority of these dogs (13/19) had transient or fluctuating ALT elevations <2 times the upper limit of the reference interval that did not progress to clinically significant liver disease during the study. A smaller group (6/19) had persistently increased ALT. Four of these dogs had elevations <4 times the upper limit of the reference interval and did not die or develop clinical signs attributable to liver disease during the study. Two dogs had elevations >4 times the upper limit of the reference interval; diagnostics indicated chronic active hepatitis and a congenital portosystemic shunt with cholangiocystitis and likely primary hepatopathy.

… The Takeaways

Key pearls to put into practice:

• In healthy patients with ALT <2 times the upper limit of the reference interval, a recheck of the liver panel after 3 to 4 weeks is reasonable prior to extensive diagnostic evaluation as long as patients remain clinically normal; ALT elevation from an acute hepatic insult usually resolves within this time frame.¹

• This study supports recommendations for further diagnostics in healthy patients with ALT ≥4 times the upper limit of the reference interval for >12 weeks.³ Abdominal ultrasonography can help guide further recommendations in these cases.

• ALT elevation is a common biochemical change in dogs with chronic hepatitis. Early diagnosis and treatment of chronic hepatitis can lead to successful management. Definitive diagnosis requires abdominal ultrasonography followed by a liver biopsy for histopathology with histochemical staining and copper quantification.²

• ALT increases of lesser magnitude and shorter duration (ie, <4 times the upper limit of the reference interval and <12 weeks duration) warrant further investigation in breeds that have shown strong evidence of increased prevalence of primary hepatopathies (eg, copper-associated hepatitis, chronic active hepatitis) in >2 studies, including Labrador retrievers, Bedlington terriers, Doberman pinschers, American and English cocker spaniels, dalmatians, West Highland white terriers, and English springer spaniels.

• At a minimum, abdominal ultrasonography should be recommended for patients with elevated ALT in combination with abnormal clinical signs, abnormalities in liver function parameters on serum chemistry profile, and/or abnormal bile acid testing results.²