Liver disease is associated with a wide range of coagulation abnormalities in dogs, cats, and humans. The liver is crucial in the regulation of platelet production, the generation of clotting factors and anticoagulant factors, and the proception of fibrinolytic enzymes. As such, animals with severe liver disease may have both thrombotic (clot-forming) and coagulopathic (bleeding) tendencies. Cats commonly experience cholestatic liver diseases, such as cholangitis and hepatic lipidosis. Traditional coagulation testing (platelet count, PT, PTT) is able to detect animals at increased risk of bleeding, but is not useful for evaluating thrombotic potential. While individual studies have looked at more specific factors (i.e. fibrinogen, D-dimer) there is a lack of data on global coagulation function in cats with cholestatic disease. Clinically, cats with liver disease have been reported to experience increased bleeding as well as thrombosis.
Thromboelastography (TEG) is a technology that is able to evaluate the entire coagulation process, including formation of the clot, maximal strength, and fibrinolysis. As such it allows a more comprehensive overview of the coagulation process and may be useful in cats with liver disease.
The purpose of this study was to describe TEG patterns in cats with cholestatic liver disease (CLD). It was designed as a prospective observational study of cats presenting to a university teaching hospital over an 18 month period. Cats were recruited if they presented with an elevated bilirubin and elevated ALT and/or ALP. They were excluded if PCV was <28%, if sedation was required for venipuncture, if they were receiving drugs known to alter coagulation (i.e. corticosteroids, anticoagulants), or if they had concurrent diseases known to alter coagulation (i.e. HCM, PLE). The cause of CLE was determined by expert analysis based on clinical signs, lab results, ultrasound, liver/bile cytology and culture, and/or histopathology.
All cats were pre-treated with vitamin K to eliminate the possibility of vitamin K induced hypocoagulability. Kaolin-0 activated TEG was run by a single operator using a standard protocol. R, K, angle, MA, G, and LY60 values were determined. PT and PTT values were also measured.
Eighteen cats fulfilled inclusion criteria and were recruited, with a median age of 9 years, 11 F/S and 7 M/N. TEG was performed on all cats. Coagulation abnormalities were present in 72% of cats based on TEG, and only 17% of cats with standard testing.
G values were used to stratify cats into one of three coagulation categories. 50% of cats were found to be hypercoaguable, 28% normocoaguable, and 22% hypocoaguable. All cats with biliary obstruction were hypercoaguable, however no other correlation with disease process was seen. 28% of cats were hyperfibrinolytic based on LY60 values.
G value was negatively correlated with ALP (suggesting animals with higher ALPs are less coagulable), and positively correlated with TS (higher proteins are more coaguable).
Three of the four hypocoaguable cats had elevated PT values, while one had an elevated PTT. Three of these cats were also considered hyperfibrinolytic, suggesting that elevated PT may be an indicator of hyperfibrinolysis in this species.
While well designed, the sample size in this study was quite small and recruited from a single, tertiary referral center. A further limitation of this study was the fairly broad exclusion criteria. Though understandable, the presence of anemia, use of concurrent medications (especially steroids) and presence of concurrent disease are common in cats presenting to veterinarians with liver disease, and as such the data shown here may not reflect a typical population. As cats were all pre-treated with Vitamin K, it is likely that the prevalence of hypocoagulability in this population is underestimated. Further studies with larger numbers of cats are needed.
The data in this study suggests that TEG may be a better test for coagulation abnormalities in cats with liver disease than standard testing (PT/PTT). While animals with higher TS and elevated PT are likely to be hypocoaguable, TEG is more sensitive for hypercoaguability and hyperfibrinolysis. Though TEG is not widely available in many practices, its use in cats with cholestatic liver disease may be useful in assessing the risk of bleeding or embolus. (MRK)