24. Vascular liver diseases, portosystemic shunt in dogs and cats. Hepatic encephalopathy Flashcards
Normal blood pressure in the portal system
5-10mmHg
Definition of portal hypertension
When the portal blood pressure is 5mmHg higher than the BP in the inferior vena cava
Composition of the portal system
Portal vein
superior mesenteric vein
inferior mesenteric vein
splenic vein
left gastric vein
umbilical vein
Aetiology of Portal Hypertension
when the blood flowing from portal system to inferior vena cava meets resistance
3 Causes of Portal Hypertension
Pre-hepatic
Intra- hepatic
Post - hepatic
Prehepatic Causes of Portal Hypertension
Occurs before blood arrives to liver
- Portal vein thrombosis
- Splenic vein thrombosis
- Arteriovenous malformation
- Splenomegaly
Intrahepatic Causes of Portal Hypertension
Occurs due to causes affecting the liver specifically
- Cirrhosis by viral hepatitis; metabolic disease; (alcohol)
- Primary sclerosing hepatitis
- Schistosomiasis
- Nodular regenerative hyperplasia
Post hepatic Causes of Portal Hypertension
due to problems involving the vena cava
- Inferior vena cava obstruction
- RS-HF
- Hepatic vein thrombosis
Clinical signs of Portal Hypertension
May be asymptomatic, usually related to underlying disease
- Hepatosplenomegaly
- Fatigue
- Nitric oxide release
- Pruritis
- Swollen capillaries
- Oedema
- Caput medusae
- Ascites
- Palmar erythema
- Jaundice
Portosystemic Shunt definition
Abnormal vascular communication between the portal and systemic venous system
Causes of PSS
acquired / congenital
Intrahepatic / extrahepatic
Consequences of PSS
Increased toxins in systemic circulation
decreased hepatic blood flow —> atrophy
Congenital PSS
75% of cases
can be intrahepatic or extra hepatic
young > old
cause of congenital PSS
abnormal embryonal blood vessels
Intra hepatic congenital PSS
solitary
persisten embryonal ductus venous
large > small dogs - wolfhound, settler, retriever, lab
extrahepatic congenital PSS
solitary
anatomically abnormal communication btw portal system and v. cava caudalis / azygous
small & toy dogs
cats, yorkies
Acquired PSS
multiplex, collateral vessels, narrowing and twisting
Protective compensatory response to portal hypertension
old > young
Hepatic Microvascular Dysplasia
congenital hypoplasia to portal vein
formation of intralobular microvascular shunts
Predisposition to Hepatic Microvascular Dysplasia
Small > large
cairn terrier, yorkie
Clinical signs of Hepatic Microvascular Dysplasia
mild / none
Diagnosis of Hepatic Microvascular Dysplasia
Increased ; BA
US
Biopsy
Treatment of Hepatic Microvascular Dysplasia
Diet
lactulose
Arterioportal fistula
connection forms between a. hepatica & v. portae
what does Arterioportal fistula lead to
Portal hypertension
ascites
acquired pss
gi oedema
clinical signs of Arterioportal fistula
continuous murmur
gi oedema
ascites
diagnosis of Arterioportal fistula
hepatic AV fistula - distended, echo loose portal branch within liver lobe
hepatofungal blood flow above liver lobe
Treatment of Arterioportal fistula
Lobectomy
treat hypertension
Hepatic venous outflow obstruction
abnormal development of vessels before differentiation into veins & arteries
diagnosis of Hepatic venous outflow obstruction
colour doppler
ex lap
celiac arteriogrphay
Lab D of Hepatic venous outflow obstruction
mild anaemia
Leucocytosis
Hypoproteinaemia
Normal liver enzymes
increased ; BA
Hepatic Encephalopathy definition
metabolic dysfunction of brain due to liver dysfunction
Hepatic Encephalopathy in younger animals
caused mostly by shunts
Hepatic Encephalopathy in older animals
caused mostly by neoplasia or cirrhosis
Acute Hepatic Encephalopathy
Rare
<10% of cases
Cause of Hepatic Encephalopathy
Liver necrosis
Clinical signs of Hepatic Encephalopathy
Seizures
semi - coma, com
increased intracranial pressure
Lab D of acute Hepatic Encephalopathy
increased ; NH3
Chronic Hepatic Encephalopathy
More common
PSS and decreased liver function
Pathophys of Chronic Hepatic Encephalopathy
PSE —> Chronic Hepatic Encephalopathy —> portosystemic vascular anastomosis —> HE
Chronic Hepatic Encephalopathy in dogs
high reserve capacity
Chronic Hepatic Encephalopathy in cats
lower reserve capacity
arginine isnt synthesized in liver –> inadequate NH3 detoxification
Final consequence of Chronic Hepatic Encephalopathy
Deranged neurotransmitter systems
Clinical signs of Hepatic Encephalopathy
graded 1- 4
cns signs due to deranged neurotransmitter systems , brain oedema, hypoglycaemia
Grade 1 of Hepatic Encephalopathy
Lethargy
Apathy
Depression
Personality Changed
Anorexia
PU
Grade 2 of Hepatic Encephalopathy
Ataxia
Disorientation
Compulsive pacing
Head pressing
Apparent blindness
Personality changes
Salivation
PU
Grade 3 of Hepatic Encephalopathy
Stupor
Severe salivation
seizures
Grade 4 of Hepatic Encephalopathy
Coma
Non responsive
Other clinical signs of Hepatic Encephalopathy
- Anorexia
- Vomiting
Weight loss - Ptyalism
- Diarrhoea
- PU/PD
- Urolithiasis
- Cystitis
- Stranguria
- Dysuria
- Haematuria
- Pollakiuria
- Crystalluria
Haematology of HE
Non regen microcytic anaemia
acanthocytes
poikilocytosis
Biochem of HE
increased ; ALP, ALT, AST, GGT, Br, BA, NH3
Decreased ; BUN, Urea, Chol, Albumin, glucose
Coagulopathy
Urinalysis of HE
Decreased ; USG
PU/PD
Ammonium biurate crystals
Urolithiasis
haematuria
proteinuria
pyuria
Liver function tests of HE
Ammonia tolerance test
Post prandial ammonia tolerance test
Fasting BA, post prandial BA
Decreased protein C
US of HE
Doppler
smaller liver
decreased size of intrahepatic veins
blood flow direction
enlarged kidneys
Angiography of HE
used to locate anatomical location of PSS
surgical catheterisation
Treatment of acute HE
treat seizures - propofol –> levetiracetam
Treat brain oedema - mannitol
fluids, electrolytes, acid - base control
to decrease NH3 and toxins - enema, lactulose
PO AB - metronidazole, amox
Gi protectants
Treatment of chronic HE
AB
Lactulose
Dont alter dietary protein intake
regular small meals
