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Associated Lectures
Moderators
Room
Hall 715
Date
07/16/19, Tuesday
Time
03:10 PM - 04:00 PM
Presentation Type
Level 1: Requires little or no prior knowledge or experience of the areas covered
Session Description
Session Sponsored by Merck

Approach to elevated liver enzymes in cats

Lecture Time
03:10 PM - 04:00 PM
Authors
Room
Hall 715
Date
07/16/19, Tuesday
Time
03:10 PM - 04:00 PM

Abstract

Abstract Body

APPROACH TO ELEVATED LIVER ENZYMES IN CATS

Susan Little, DVM, DABVP (Feline)

Bytown Cat Hospital, Ottawa, Ontario, Canada

catvet@vin.com

@catvetsusan

Liver function tests

-Serum bilirubin, especially when >51 µmol/L (3 mg/dL)

-Biomarkers that change late in disease include glucose, cholesterol, blood urea nitrogen, albumin

-Aminotransferase enzymes

-ALT: half-life in cats is 3-6 hours (vs 60 hours in dogs); hemolysis & lipemia will cause false elevations

-AST: Liver, skeletal & cardiac muscle; half-life in cats is ~1 hour (vs 12 hours in dogs)

-Cholestatic enzymes

-ALP: bone, kidney, intestine, liver; half-life in cats is 6 hours (vs 66 hours in dogs)

-GGT: kidney, pancreas, intestine, liver; half-life probably <1 hour

-Induction of liver enzyme increases secondary to drugs (corticosteroids, phenobarbital) rare in cats compared to dogs

Diagnostic approach

-Most common liver diseases in cats are cholangitis syndrome, hepatic lipidosis, neoplasia; other causes include parasites, FIP, abscess, amyloidosis, cystic disease, acute toxic insult, etc.

-Minimum database (complete blood count, serum chemistry panel, total T4, urinalysis, FeLV/FIV): necessary to determine if elevations are hepatic or non-hepatic in origin.

-Gastrointestinal function tests: cobalamin, folate, fTLI, fPLI

-Hepatobiliary causes of increases in ALT, AST include drugs, infection, inflammatory disease, inherited disease, neoplasia, portosystemic shunt, toxins, trauma

-Non-hepatic causes of increases in liver enzymes include

-Common: diabetes mellitus, hyperthyroidism, pancreatitis, inflammatory bowel disease, systemic infections (e.g., dental disease)

-Uncommon: congestive heart failure, severe hemolytic anemia, abdominal trauma, neoplasia

-Serum bile acids can be used to confirm hepatobiliary disease is present (don’t perform if serum bilirubin is elevated); fasting (12 hours) + post-prandial (2 hours); does not give information on diagnosis or disease severity.

-Urine bile acids:creatinine ratio: single random urine sample (2 mL, no hematuria); ratio >4.4 is evidence of hepatic disease.

-Other diagnostic tests may be necessary to rule in/out hepatobiliary disease: imaging (radiographs, ultrasound), biopsy (percutaneous ultrasound-guided, laparoscopic, surgical laparotomy).

-Liver biopsy options:

-At least 6 portal areas necessary to diagnose inflammatory disease (~15 mg tissue)

-Consider evaluation of coagulation, administration of vitamin K1 before biopsy

-Fine needle aspirate: inexpensive, easy to perform; low risk, may only require sedation; small sample size (3-5 mg); only ~50% agreement with histopathology; best for diffuse lesions such as lipidosis, lymphoma, fungal disease

-Ultrasound-guided percutaneous needle core biopsy: requires general anesthesia; higher risk of liver trauma, fracture than with FNA, surgery, laparoscopy; use only manual or semi-automatic biopsy devices; good sample size, collect 2-3 samples from different lobes

-Surgical or laparoscopic biopsy: best visualization but most invasive, largest sample size, multiple sites and organs can be biopsied; best ability to monitor sites for bleeding

-Optimizing liver biopsy: collect multiple samples, collect bile for culture & cytology, give the pathologist a complete history.

-Contraindications for liver biopsy: platelets <80,000/mL, prolonged buccal mucosal bleeding time (>150 seconds), PT or APTT >2 times upper normal limit, infectious disease that could be disseminated, ascites.

-Post-biopsy patient care: monitor carefully for 6-12 hours (attitude, mucous membrane colour, capillary refill time, blood pressure, hematocrit), provide analgesia

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Non-specific treatments

-S-adenosyl-l-methionine (SAMe): ‘supernutrient’ for the liver, essential part of 3 major biochemical pathways, helps increase hepatic glutathione, no known contraindications, appears to be safe

-Silymarin: anti-oxidant, free radical scavenger, inhibits effects of tumour necrosis factor, helps increase hepatic glutathione, no known contraindications, appears to be safe

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