equine liver

what is an important clinical question

whether the horse has an acute liver injury with the potential for recover

or chronic liver disease that has acutely decompensated

what are liver function tests

direct bilirubin, bile acids, blood ammonia, Pt/PTT

When do liver function tests become abnormal

when 70-80% of the hepatic function has been lost

what two types of injury do liver specific enzymes help to characterize

hepatocellular vs biliary

does the magnitude of liver specific enzyme elevation correlate with hepatic function?

no they detect injury but do not assess function, and they should not be interpreted in isolation

what are unique findings of horses with severe liver disease

-increased hematocrit

-serum iron concentration

-transferrin saturation that persists despite rehydration

special consideration for anorexic of fasted horses

fasting induced hyperbilirubenaemia and mild icterus is common

fasting for 2-3 days can also increase serum bile concentrations

special considerations for racehorses

increased GGT activity has been associated with poor performance and maladaptation to training

with GGT lowering during periods of rest

special considerations for foals

GGT is present only in low concentrations in equine oclostrum

therefore increased GGT activity reflects endogenous productions rather than from colostrum

serum ALP is increased bc of growth for first year of life

serum bile acid concentrations are higher than adults for first 6 months

what are the three liver specific enzymes tested in horses

GGT

GLDH

SDH

what are the liver specific hepatocellular enzymes

GLDH and SDH

ALT

How do GLDH and SDH differ

SDH has a shorter half life making it useful for monitoring progress or resolution. common in US

GLDH more common in NZ

what enzyme assess biliary disease

GGT

what are the non liver specific enzymes

ALP and AST

what can affect AST

hepatocellular, muscle or erythrocyte

what affects ALP

liver, bone, corticosteroid

what is the most common metabolic cause of liver failure in horses

hepatic lipidosis and hyperlipemia

when does hepatic lipidosis occur

when a negative energy balance activate hormone sensitive lipase in adipose tissue, resulting in excessive mobilization of NEFAs. the liver becomes overwhelmed by the influx of fat, leading to triglyceride accumulation within hepatocytes and increased circulating triglyceride concentration

what animals are at risk of hepatic lipidosis and hyerpliparmia

Shetland and welsh mountain ponies, mini horses, donkeys, obese animals, horses with EMS or PPID, pregnant or lactating mares, horses experiencing stress

when can hyperlipemia occur as a primary disease

in ponies and donkeys

why is hyperlipemia not a primary disease in horses

usually secondary to an underlying disorder causing negative energy balance

what are the clinical signs of hyperlipemia, and hepatic lipidosis

-progress rapidly from anorexia, lethargy, weakness → ataxia, head pressing, recumbency, seizures, and death

-ventral edema, icterus, and reduced gastrointestinal motility may also be present

-without treatment death often occurs within 6-10 days of onset

how do you diagnose hyperlipemia and hepatic lipidosis

hypertriglyceridaemia (>5mm/L)accompanied by compatible clinical signs is diagnostic

gross lipemia of centrifuged plasma provides a useful stall side clue

liver enzyme activités (GGT, GLDH, SDH) are variably increased

what does lipemia describe

the appearance of serum

will all horses with hypertriglyceridaemia have hyperlipemia

no

but all horses that have hyperlipemia will have severe hypertriglyceridaemia

Treatment of hyperlipaemia and hepatic lipidosis

is challenging and often requires referral for hospitalisation for intensive nutritional support, including enteral or parenteral nutrition and insulin therapy.

careful monitoring of blood glucose is essential to avoid hypoglycemia

identifying the underlying and correcting the identifying cause of the negative energy balance

prognosis of hyperlipaemia and hepatic lipidosis

poor

reported mortality of 57-85%

animals with serum triglyceride concentrations <5mmol/L have substantially greater prognosis

what can be added to treatment for a PPID associated hyperlipemia

pergolide in addition to supportive care

prevention of hyperlipemia

identify at risk animals and manage obesity

recognize and manage endocrine disease

avoid prolonged negative energy balance

monitor serum triglyceride concentrations

a mini horse develops hyperlipemia following several days of anorexia. the primary goal of treatment is to:

increase endogenous insulin secretion to suppress hormone sensitive lipase

how does liver disease often present

subtle, non specific signs such as weightloss, mild colic, icterus, and occasional fever

clinical examination and clinicopathological testing help identify hepatic involvement

what body systems can present with the trait of colic, pyrexia, and icterus

1. hepatic system (most likely)

2. GI (severe enteritis or colitis)

3. respiratory system (pleuritis or pleuropneumonia)

4. haemopoietic system (IMHA) but colic not typical

what is the most common clinically significant biliary disease in horses

cholangiohepatitis caused by ascending bacterial infection from the duodenum

what does cholangiohepatitis predispose to and why

calcium bilirubinate cholelithiasis

1. bacterial infection causes bilirubin deconjugation

2. calcium bilirubinate crystals form

3. biliary sludge develops

4. choleliths form around a glycoprotein matrix

clinical signs of cholangiohepatitis

fever, icterus, recurrent (often mild colic), and weightloss

diagnosis of cholangiohepatitis

marked increases in GGT and ALP

conjugated biliruben of >25% of total bilirubin supports biliary obstruction

ultrasound of sludge, dilated bile ducts or choleliths

liver biopsy and culture provide definitive diagnosis

treatment of cholangiohepatitis

prolonged antimicrobial therapy ideally guided by culture

ursodiol may improve bile flow and reduced inflammation

continue treatment until GGT and ALP remain normal for 2-4 weeks

surgery is reserved for complete biliary obstruction or selected cases with accessible choleliths

prognosis of cholangiohepatitis

good if there is clinical improvement within 7-10 days and minimal hepatic fibrosis

and that it has successfully been distinguished from cholelithiasis as these carry a much more guarded prognosis

what is chronic active hepatitis

a progressive peri portal inflammatory liver disease of uncertain cause

clinical signs of chronic active hepatitis

often subtle and intermittent, and may include fever

moist exfoliative dermatitis of the coronary bands can occur and may reflect immune mediated vasculitis or photosensitization

hepatic encephalopathy can develop

clinicopathological findings of chronic active hepatitis

cholestatic liver disease,

evidence of inflammation (leukocytosis left shift and monocytosis)

liver biopsy is essential for diagnosis and prognosis

histopathology of chronic active hepatitis

peri portal fibrosis with neutrophilic or lymphocytic inflammation

concurrent cholangiohepatitis is common and may be either a cause or consequence of the disease

treatment of chronic active hepatitis

corticosteroids (effective but 50% relapse)

antibiotics if concurrent cholangiohepatitis is present

colchicine and zinc if progressive fibrosis is identified

ursodiol for cholestasis

what is equine hepacivirus

a close relative to human hepatitis C, is a recognized cause of acute and chronic hepatitis in horses

what is the expected histopathology of equine hepacivirus

fibrosis, lymphocytic inflammation, hepatocellular necrosis, and ductular reaction

what is the treatment and prognosis of equine hepacivirus

no treatment shown to consistently eliminate infection

guarded prognosis

what are the most common primary hepatic tumors

cholangiocarcinoma

hepatoblastoma

the liver is a frequent site of metastasis for what cancers

lymphoma

SCC

melanoma

what is unique of ascites in relation to the liver in horses

it is uncommon in equine liver failure

its presence should raise suspicion for neoplasia or concurrent peritonitis

is hemorrhage a risk of liver biopsy?

there is no significant association between abnormal coagulation tests and post biopsy complications

what kind of bacteria are equine hepatobiliary infections caused by

enteric gram negative and anaerobic bacteria