portocaval anastomoses
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PORTOCAVAL ANASTOMOSES
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PORTOCAVAL ANASTOMOSES
Abdominal Veins
Portal Vein
Inferior Caval Vein The Heart
Hepatic Veins
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Blood supply
Liver receives 25% of resting cardiac output
Blood enters via hepatic artery (25%) & portal
vein (75%) carries blood from gut rich in absorbed nutrients portal flow increases after
meals Blood leaves via
hepatic vein Also leaving liver
hepatic ducts carry bile to gall bladder
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Veins to form Portal Vein System
1. Vena Lienalis
2. Vena Mesenterica
superior
3. Vena Mesenterica
inferior
4. V. Gastrica sinistra
5. V. Gastrica dextra
6. V. Cystica
7. V.Parumbilicalis
( Venae of superficial abdominal wall, surrounding the umbilicus )
1
2
3
45
6
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Structures entering PORTA HEPATICA
1. A. Hepatica Propria
2. V. Porta Hepatica
3. Ductus hepaticus communis
3 2 1
Portal Triad
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Within the liver the portal vein divides, first into left and right main branches and then further small branches supply each acinus or lobule. These portal venous blood flows through the hepatic sinusoids and exits the liver through terminal hepatic venules, which join to form the hepatic veins, rejoining the systemic circulation at the inferior vena cava
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PORTALTRIBUTARIES
SYSTEMICTRIBUTARIES
v Gastrica Sinistra V. Oesophagealis
V. Rectalis superior V. Rectalis inferior
V. ParumbilicalisVv. Epgastricae
Vv. Retro peritonealis
Vv.Colicae
PORTOCAVALANASTOMOSES
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V. Rectalis medialis
4
2
3
1
CAVAL SYSTEM = SYSTEMIC SYSTEM
PORTAL SYSTEM
v. Azygos
V. Oesophagica
LIVER
V.Porta Hepatis
V. Gastrica sinistra
V.Lienalis
V.M
esenterica superior
V.Mesenterica inferior
V.Colica
V.C
ava
Infe
rio
r
V.Parumbilicalis
V.Epigastrica superf
V.Rectalis superior
V.Rectalis inferior
Vv.Retroperinealis
V.Hepatica
PORTO-CAVAL ANASTOMOSES
2
1 Varices Oesophagus
Caput Medusae
Hemorrhoids
4
3
Ascites
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- Once again, inflow to the liver involves oxygenated blood via hepatic arteries and absorbed nutrients and compounds from the GI tract via the hepatic portal veins.
- All venous drainage from the GI tract and abdominal visceral organs enters the portal system back to the liver. The overall order is as following: arteries → capillaries → veins → portal vein → hepatic sinusoids → veins → vena cava → heart.
- In contrast, the caval system is as following: arteries → capillaries → veins → vena cava → heart. Obviously, this is the circulatory system within the rest of the body.
- The portal and caval system are not exclusive from each other. There are 4 sites of portocaval anastomoses:- 1) esophageal veins- 2) paraumbilical veins- 3) rectal veins- 4) retroperitoneal veins
- If there is liver damage or cirrhosis – accumulation of fibrous tissue that constricts the sinusoids – there may be portal hypertension. This may lead to varicose veins at the 4 sites of anastomoses.
Resume
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Portal Hypertension Portal hypertension causes splenomegaly. Portosystemic shunting causes varices to form. The blockade in V, oesophagus may result ini Varices Oesophagus.
When it rupture may causing massive, life-threatening gastrointestinal haemorrhage. This usually causes haematemesis.
The rupture of rectal veins may result in Melaena or Haemorrhoid bleeding.
The blockade in Venae parumbilicales may result in the formation of Spider Naevi
Ascites is the accumulation of fluid in the peritoneal space. Portal hypertension increases hydrostatic pressure in intestinal and mesenteric capillaries, causing fluid leakage.
Encephalopathy is caused by shunting of toxins to the systemic circulation, releasing excess amino acids that are broken down to release ammonia, which contributes to the encephalopathy.
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Complications of ALD – Portal hypertension
Increased resistance to flow through the portal system blood forced down alternate channels
Collateral circulation Portosystemic
shunting
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Consequences of portal hypertension
Ascites Hepatic encephalopathy Increased risk of spontaneous
bacterial peritonitis Increased risk of hepatorenal
syndrome Splenomegaly-mild
panyctopenia Portacaval anastomoses
(oesophageal varices, haemorrhoids, caput medusae)
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Complications of CLD – Ascites
Caused by: ↓ albumin Portal hypertension ↓ renal perfusion Na/water retention ↑ aldosterone
Treatment: Diuretics (spironolactone/frusemide) Ascitic taps shunts
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