SA Icterus and Hepatic Encepalopathy Flashcards
What are the 3 forms of icterus?
- Pre-hepatic (conjugation ad uptake of bilirubin -> liver overwhelmed)
- Hepatic (uptake, conjugation and excretion in hepatocytes overwhelmed)
- Post-hepatic (conjugation, excretion and uptake back into liver overwhelmed: CHOLESTASIS)
What IS icterus
Hyperbilirubinaemia
Where does the majority of bilirubin come from?
Senescent erythrocytes
What is newly formed bilirubin bound to? Why? When does it dissociate?
- Albumin
- Insoluble in water until conjugated in liver
- Dissociates before entering hepatocytes
What is bilirubin conjugated with in the liver?
Glucuronic acid
What is the rate limiting step of bile production?
Conjugation of bilirubin with glucuronic acid -> water soluble for excretion in urine
What are the Ddx for pre-hepatic anaemia?
> Haemolysis
- Babesia
- IMHA
- Toxins [Onions, lead, copper]
What history/PE findings indicate liver problems?
> GI - VD+ - Acholic feaces (white, indicates POST-HEPATIC) - Melaena (not sure why but commonly associated) - Ascites (portal hypertension) > Neuro (hepatic encepalopathy) - Personality change - Ptyalism in cats - Head pressing - Disorintation - Seizures - Stupor > Renal/uro - PUPD - Pollakuia (small, freq) - Stranguria (urgency) - Dysuria (difficulty) [ammonium urate crystals] - Billirubinuria > Heamatologic - Pale mms (anaemia due to GI haemorhage/chronic diseas [usually mild]/coagulation disorders/haemolysis)
Why are renal signs seen with liver problems
Build up of ammonium in blood -> formation of ammonium urate stones -> bloackage
What are he Ddx for hepatic icterus in the cat?
> Cat
- Suparative cholangiohepatitis
- Lymphocytic plasmacytic hepatitis
- Hepatic lipidosis (metabolic)
- Feline infectious peritonitis (viral, young cats, systemic disease)
- Toxins (Acetaminophen, aspirin)
- Neoplasiaggyg
What are the Ddx for hepatic icterus in the dog?
> dog
- Acute liver disease (toxins or drugs)
- Leptospirosis (also -> renal failure)
- Chronic hepatitis (may not -> icterus as generally long tem end stage liver failure)
- Neoplasia
What are the Ddx for post-hepatic icterus?
> Dogs and cats
- Pancreatitis -> leakage of enzymes, sever local peritonitis -> blockage of duodenal papilla
- Neoplasia (liver/duodenum/pancreas)
- Cholelithiasis (uncommon, usually 2* to cholangiohepatitis)
How would you differentiate between pre-hepatic and hepatic icterus?
> Bloods
- Pre: PCV low, TP normal
- Hepatic: PCV normal, TP low (if albumen low)
How would you differentiate hepatic and posthepatic icterus?
> Imaging
- Ultrasound/contrast radiographs to rule out post-hepatic
What diagnostics can be used to work up hepatic disease once pre- and post- have been ruled out?
- Heam/biochem/UA
- Liver FUNCTION
- Coagulation tests (esp important prior to biopsy)
- Abdo ultasound
- Aspirate effusion, cytology (ascites)
- Liver FNA
- FNA and culture of bile
- Liver biopsy: histo, culture
What can liver FNA diagnose? What may be needed following this?
- Lymphoma and hepatic lipidosis ONLY
- No other Dx can be made
- Require biopsy
What do raised liver enzymes indicate?
- Damage to liver cells
- Mostly reversible hepatocyte damage
Give 3 liver enzymes that may be used to evaluate liver health. How liver specific are these?
- ALT: liver specific
- AST: also present in muscle, intestine etc.
- AP: Specific to biliary duct cells throughout liver BUT isoenzymes may falsely raise levels (cortisol-induced in dogs, bone, intestine, placenta) -> look to see if AP ^ MORE than other liver enzymes, would indicate biliary duct cells affected.
What findings on routine biochem and heamatology indicate liver failure?
- low albumen
- low cholesterol
- low glucose
- low BUN (blood urea nitrogen)
Which test specifically links to liver function?
Bile acids
- produced in liver from cholesterol and recycled in enterohepatic circulation so SHOULD NOT enter systemic circulation.
- If not re-uptaken into liver hepatocytes, congestion in portal vein -> overflow -> ^ bile acids in systemic circulation
> First measurement fasted, then fed, measured post-prandial.
> indicates liver failure OR pss
Where should bile be present in the GIT?
Released from duodenal papilla
Reuptaken in ileum
What 2 substances are the main causes of hepatic encepalopathy?
- NH3
- Aromatic AAs
> released in digestion of proteins
> neurotoxic
> should be metabolised by liver
> instead shunted to systemic ciculation and able to cross BBB
What are the clinical signs associated with hepatic encepalopathy?
> CNS - Bizarre behaviour - Head pressing - Seizures - Intermitent blindness - Ptyalism in cats > Renal/uro - urate stones -> dysuria, pollakuria, stranguria (^ blood ammonium -> decreased ability to convert uric acid -> allantoin in liver -> more urate excreted in urine)
Give he 4 most common causes of hepatic encepalopthy in cats
- acute liver failure (toxic)
- Hepatic lipidosis
- Neoplasia
- PSS (rare in cats)
