Icterus/HE in small animals

Question 1

In what form in newly formed unconjugated bilirubin?

Answer 1

insoluble in water, bound to albumin, dissociates from this before entering liver cell

Question 2

What happens to bilirubin in the liver cell?

Answer 2

Conjugation with glucoronic acid making it water-soluble for excretion in urine (rate limiting step in hepatocyte)

Question 3

What do bacteria in the lower urinary tract do?

Answer 3

convert bilirubin into urobilinogen –> enterohepatic circulation

Question 4

Define pre-hepatic icterus

Answer 4

conjugation and uptake of bilirubin into liver overwhelmed

Question 5

Define hepatic icterus

Answer 5

uptake, conjugation and excretion of bilirubin in hepatocytes overwhelmed

Question 6

Define post-hepatic icterus

Answer 6

conjugation, excretion and uptake back into liver overwhelmed

Question 7

What signs might show clinical signs of icterus? 4

Answer 7

• GIT
• neurologic
• renal/urinary
• haematologic

Question 8

GIT signs 4

Answer 8

• vomiting and diarrhoea (common)
• acholic faeces (i.e. white)
• melaena
• ascites

Question 9

Neuo signs of HE 6

Answer 9

• personality change
• ptyalism (drooling, cats)
• head pressing
• disorientation
• seizures
• stupor

Question 10

Renal signs 6

Answer 10

Pu/PD (insufficient urea to concentrate)
pollakiuria
stranguria
dysuria
bilirubinuria

Question 11

Define pollakiuria

Answer 11

excessively high daytime frequency of urination

Question 12

Define stranguria

Answer 12

slow, painful urination caused by mm spasms of the urethra and bladder

Question 13

Define dysuria

Answer 13

painful micturition

Question 14

Haematologic signs 6

Answer 14

• yellow animal
• pale MM
• anaemia from GIT haemorrhage
• anaemia of chronic disease
• coagulation disorder
• haemolysis

Question 15

DDx for pre-hepatic icterus

Answer 15

Haemolysis (IMHA, babesia infection, toxins - onions, lead , copper)

Question 16

DDx for hepatic icterus - CAT 6 (in order of likelihood)

Answer 16

• suppurative cholangiohepatitis
• lymphoplasmacytic hepatitis
• hepatic lipidosis
• FIP
• toxins (acetaminophen=paracetamol, aspirin)
• neoplasia

Question 17

DDx for hepatic icterus - DOG 4 (in order of likelihood)

Answer 17

• acute liver disease
• leptospirosis
• chronic hepatitis
• neoplasia

Question 18

DDx for post-hepatic icterus (both dogs and cats) 3

Answer 18

• pancreatitis
• neoplasia (liver, duodenum, pancreas - i.e. close anatomic proximity)
• cholelithiasis (uncommon in cats/dogs)

Question 19

How do you differentiate pre-hepatic and hepatic icterus? 2

Answer 19

PCV and TS (Prehepatic: PCV is low, TS normal. Hepatic - PCV usually normal, TS can be low if albumin is low)

Question 20

How do you differentiate hepatic and post-hepatic icterus?

Answer 20

Imaging (what the bile duct looks like, what’s blocking it perhaps, pancreatitis etc.)

Question 21

Describe the workup for hepatic diseases - 8

Answer 21

• haematology, chemistry profile, UA
• liver function tests
• coagulation tests
• abdominal ultrasound
• aspirate effusion, cytology
• liver fine needle aspirate
• fine needle aspirate and culture of bile
• liver biopsy (histology, culture)

Question 22

What is the most specific liver enzyme?

Answer 22

ALT (increased means increased numbers of hepatocytes are dying)

Question 23

Where is AST present?

Answer 23

Liver but also the mm and intestines

Question 24

What is AP and where is it found?

Answer 24

Alkaline phosphatase. Found in biliary duct cells (which are throughout the liver). Isoenzymes of this are cortisol-induced (dogs only) in bone, intestines, liver, placenta etc

Question 25

Indications for liver failure on biochemistry - 4

Answer 25

-Low albumin -Low cholesterol -low glucose -low BUN (be sure to run a bile acid test as well)

Question 26

Where are bile acids produced? From what?

Answer 26

in liver from cholesterol

Question 27

How do bile acids return to the liver after secretion into small intestine?

Answer 27

enterohepatic circulation

Question 28

How do you measure bile acids? When do levels of this change?

Answer 28

Take two measurements: 1st = fasted Give food then take 2nd measurement The rate limiting step ins the re-uptake of bile acids from the blood into hepatocytes. Levels are elevated in liver failure and PSS.

Question 29

What is HE

Answer 29

ammonia and aromatic AA go directly into blood without passing through liver first means the CNS is exposed to shunted gut-derived toxins

Question 30

Neurologic signs of HE - 5

Answer 30

- bizarre behaviour - head pressing - seizures - intermittent blindness - ptyalism (cats)

Question 31

Signs of urate stone formation 3

Answer 31

dysuria, stranguria and haematuria

Question 32

Clinical sign of HE

Answer 32

urate stone formation

Question 33

Pathogenesis of urate stone formation

Answer 33

increased ammonium concentration in blood, decreased ability to convert uric acid to allantoin in the liver --> more urate excreted in urine

Question 34

Most important diseases causing HE in CATS - 4

Answer 34

acute liver failure (toxic) hepatic lipidosis neoplasia PSS (v rare in cats)

Question 35

Most important diseases causing HE in DOGS - 3

Answer 35

``` PSS liver failure (acute) - toxic, infectious liver failure (chronic) - cirrhosis ```

Question 36

In hepatic acidosis, how can FFA and Tg be processed by liver? When doesn't this work? Treatment?

Answer 36

- B oxidation - redistribution to other organs via lipoproteins (especially VLDLs) - doesn't work if diet is protein-deficient. Treatment therefore requires force-feeding (stomach tube) diet which is high in protein.

Question 37

How do you test for liver function?

Answer 37

bile acids (remember 2 readings). Not liver enzymes as these won't tell you if the whole liver is working.

Question 38

What are classic biochemistry signs for HE? 3

Answer 38

low glucose and urea, high bile acids (latter confirms hepatic dysfunction)

Question 39

DDx for seizures/strong reaction to normal diazepam dose, decreased mentation, lethargy, weakness, inappetence?

Answer 39

INTRACRANIAL: - anomaly (hydrocephalus, lissencephaly) - infection (distemper, toxoplasma, parasites) - idiopathic epilepsy - trauma METABOLIC: - EXOGENOUS - toxic - medications - ENDOGENOUS - HE because PSS, uraemia, electrolyte disturbances, hypoglycaemia