39. Icterus – differential diagnosis & diagnostic approach, management

What is icterus/jaundice?

Yellowish discoloration of the skin, mucous membranes, and sclera, caused by elevated levels of bilirubin in the blood (hyperbilirubinaemia, >17 mmol/L)

What is bilirubin?

An orange bile pigment produced by the breakdown of haem

What are the three types of icterus?

Pre-hepatic, hepatic, and post-hepatic

What is pre-hepatic icterus?

Increased production of bilirubin due to massive haemolysis

What are some causes of pre-hepatic icterus?

Autoimmune haemolytic anaemia, blood transfusion reactions, blood parasites (Babesia, Dirofilaria), infections (Leptospirosis), and intoxications (onions, paracetamol, plant poisons)

What is the pathogenesis of pre-hepatic icterus?

Excessive RBC damage causes haemolysis and excessive release of haemoglobin into the blood. Haemoglobin is transformed into bilirubin, and the excessive amount of bilirubin cannot be excreted by the liver, leading to a build-up in the blood, faeces, and urine

What are some clinical signs of pre-hepatic icterus?

Yellow mucous membranes, weakness, dyspnoea, dark faeces, and dark urine

What is hepatic icterus?

Damage to liver cells resulting in failure to take up, conjugate, or excrete bilirubin

What are some causes of hepatic icterus?

1. Inherited conditions (Gilbert's disease)

2. Acute damage to liver cells: infection, inflammatory disease (hepatitis, cholangiohepatitis), tumours, toxins (chemical, plant, metabolic), and parasites (migrating larvae, Toxoplasma)

What is the pathogenesis of hepatic icterus?

Bilirubin enters and accumulates in the blood, faeces, and urine

What are some clinical signs of hepatic icterus?

Fever, vomiting, anorexia, diarrhoea, icterus of mucous membranes, haemorrhages, and pale and foul-smelling faeces

What is post-hepatic icterus?

Icterus occurring secondary to reduced or blocked drainage of bile into the duodenum

What are some causes of post-hepatic icterus?

Inflammation of bile ducts, thrombosis, sclerosis, compression (mass, abscess), and obstruction (stones, parasites, mass)

What are examples of parasites causing post-hepatic icterus?

1. Plastynosomum fastosum

2. Opisthorchis

What is the pathogenesis of post-hepatic icterus?

Bilirubin accumulates in the liver and refluxes into the blood

What are some clinical signs of post-hepatic icterus?

Similar to hepatic icterus. Fever, vomiting, anorexia, diarrhoea, icterus of MM, haemorrhages, pale & stinky faeces.

What is the diagnostic approach to icterus?

1. History and anamnesis, physical examination

2. Laboratory examination, biopsy

3. Imaging methods

What are examples of laboratory testes used in the diagnostic approach to icterus?

1. CBC

2. Biochemistry

3. Van den Bergh test

4. Urinalysis

What complete blood count findings are associated with icterus?

Regenerative anaemia (pre-hepatic) and non-regenerative anaemia (hepatic)

What biochemical findings are associated with icterus?

Increased liver enzymes (ALP, ALT, GGT), albumin, glucose, and cholesterol

What is the significance of high levels of GGT in the blood?

It is one of the first signs of liver disease or damage to the bile ducts

What is the Van den Bergh test used for?

To differentiate conjugated from unconjugated bilirubin in serum. Non-conjugated (pre-hepatic), both (hepatic), and conjugated (post-hepatic)

What urinalysis finding is associated with icterus?

Bilirubinuria (may be physiological in dogs)

What imaging methods are used to investigate icterus?

Radiography (liver enlargement) and ultrasound (neoplasia, lipidosis (hyperechoic), congestion (hypoechoic), cholelithiasis)

How is icterus managed?

1. Stabilisation (fluid therapy, correction of CNS signs (propofol, NOT benzodiazepines) and hypoglycaemia)

2. Antibiotics (ampicillin)

3. Low-protein diet

4. Treatment of the underlying cause

How is pre-hepatic icterus due to autoimmune anaemia treated?

Glucocorticoids and cyclosporine

How is pre-hepatic icterus due to infectious agents treated?

Tetracycline (Leptospirosis) and imidocarb (Babesia)

How is hepatic icterus due to infectious agents treated?

Antibiotics and supportive care

How is hepatic icterus due to intoxicants treated?

Antidotes

How is hepatic icterus due to autoimmune causes treated?

Corticosteroids

What supportive care is given for hepatic icterus?

Antioxidants (ursodiol, adenosyl, vitamin E, silymarin), Hepacyl, and hepatic diets

What is the treatment for post-hepatic icterus?

Usually need surgery to remove blockage or repair rupture

What are examples of systemic antibiotics used?

1. Beta-lactams: penicillins, cephalosporins

2. Aminoglycosides: streptomycin, amikacin, gentamycin

3. Enrofloxacin

4. Clindamycin

What antibiotics are used in the case of hepatic encephalopathy?

1. Neomycin

2. Metronidazole