40. Hepato-encephalopathy, Portosystemic shunt – causes, diagnostic, therapy

What is hepatic encephalopathy (HE)?

A metabolic disease affecting the CNS that occurs as a result of severe liver disease and increased ammonia in the blood

What are some aetiologies of HE?

1. Portosystemic shunting (most commonly)

2. Hepatic failure

3. Cirrhosis

What is the pathogenesis of HE?

Due to liver failure, the liver cannot remove toxins from the blood. Ammonium and glutamate accumulate in the blood, cross the blood-brain barrier, damage brain astrocytes, and cause brain oedema

What are some clinical signs of HE?

Mental abnormalities (head pressing, circling, apathy, seizures), restlessness, coma, vomiting, PU/PD, diarrhoea, and ascites

How is HE diagnosed?

1. Haematology (microcytic anaemia, increased blood ammonia, prolonged clotting time)

2. Biochemistry (decreased urea, creatinine, glucose, cholesterol, albumin; increased liver enzymes, ammonia, bile acids)

3. Urinalysis (low urine specific gravity, presence of ammonium urate crystals)

4. Imaging methods (radiography, ultrasound, FNA, biopsy, abdominocentesis)

How is HE treated?

1. Antibiotics (neomycin, amoxicillin, metronidazole)

2. Lactulose, enema, gastric lavage (removal of neurotoxins in GIT)

3. Zinc

4. Mannitol

5. Fluid therapy

6. Vitamin K

7. Decreased protein diet.

Prognosis is often poor

What is a portosystemic shunt (PSS)?

A portosystemic vascular anomaly—a venous malformation where abnormal vessels connect the portal and systemic circulation, allowing portal blood to bypass the liver

What are the two main types of PSS?

Congenital and acquired

What are the two types of congenital PSS?

Intrahepatic and extrahepatic

Which breeds are predisposed to intrahepatic congenital PSS?

Large breeds like Irish Wolfhounds and English Sheepdogs

Which breeds are predisposed to extrahepatic congenital PSS?

Small breeds like Yorkshire Terriers, Maltese, Tibetan Terriers, and cats

What causes acquired PSS?

1. Secondary to primary liver disease (hepatic cirrhosis)

2. Portal hypertension (fibrosis, cirrhosis, obstruction of bile ducts)

What is the pathogenesis of PSS?

1. Reduced blood flow to the liver (causing ischaemia and nutrient depletion)

2. Reduced detoxification and function of hepatocytes (leading to increased ammonia and hypoalbuminaemia, potentially causing ascites)

3. Alternative pathways through the oesophageal vein (which can rupture due to thin walls)

What are some clinical signs of PSS?

Normal appearance, stunted stature ("mini Yorkshire"), microencephalopathy, and hepatic encephalopathy

How is PSS diagnosed?

1. Anamnesis and history (episodes of HE starting at weaning (congenital), retarded growth, weakness, behaviour changes, vomiting, diarrhoea, PU/PD, dysuria, seizures, GIT ulcers, and lower urinary tract obstruction)

2. Haematology (non-regenerative anaemia)

3. Biochemistry

4. Urinalysis

5. Imaging

What key biochemical findings are associated with PSS?

1. Increased fasting serum bile acids (FSBA) and increased ammonia

2. ALP and ALT may be normal (if congenital and no secondary damage)

3. Low urea, creatinine, cholesterol, glucose, and albumin

What urinalysis findings are associated with PSS?

Blood, pus, protein, and ammonium biurate crystals

What imaging techniques are used to diagnose PSS?

Ultrasound (Doppler), FNA, biopsy, and abdominocentesis

How is PSS treated?

Supportive care, a low-protein diet, treatment of HE, and surgery (if congenital)

What is important on the bloods apart from normal liver parameters?

Ammonia

What breeds are predisposed for portosystemic shunts?

Yorkshire terrier and other small breeds

What is a specific test for hepatobiliary disease (HE/PSS)?

• Fasting serum bile acid (FSBA): after fasting for 12 hours

• Post-prandial serum bile acid (PSBA): 2 hours after meal

Bile acids go up