PORTOCAVAL ANASTOMOSES

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

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 )

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Structures entering PORTA HEPATICA

1. A. Hepatica Propria

2. V. Porta Hepatica

3. Ductus hepaticus communis

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Portal Triad

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

PORTALTRIBUTARIES

SYSTEMICTRIBUTARIES

v Gastrica Sinistra V. Oesophagealis

V. Rectalis superior V. Rectalis inferior

V. ParumbilicalisVv. Epgastricae

Vv. Retro peritonealis

Vv.Colicae

PORTOCAVALANASTOMOSES

V. Rectalis medialis

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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

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1 Varices Oesophagus

Caput Medusae

Hemorrhoids

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Ascites

- 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

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.

Complications of ALD – Portal hypertension

Increased resistance to flow through the portal system blood forced down alternate channels

Collateral circulation Portosystemic

shunting

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)

Complications of CLD – Ascites

Caused by: ↓ albumin Portal hypertension ↓ renal perfusion Na/water retention ↑ aldosterone

Treatment: Diuretics (spironolactone/frusemide) Ascitic taps shunts