Hepatic Circulation - Functions, Dysfunction, Causes, and Treatment

Introduction:

Hepatic circulation is a unique system that has a double blood supply. It receives oxygenated blood from the hepatic artery and deoxygenated (oxygen deficit blood) blood from the portal vein. The dysfunction of hepatic blood flow can be obstruction of the hepatic inflow, obstruction to blood flow through the liver, and obstruction to hepatic vascular outflow. It can be due to a block by a blood clot or due to an underlying disease like cirrhosis (scarring of liver cells).

What Is A Liver?

The liver is an internal organ and is larger than any other organ in the body. It is located in the right upper region above the stomach. The liver is also called a gland because it produces chemicals (like bile) needed for the body. The liver produces a dark green-yellowish-brown fluid called bile. This bile is released by the liver into the gallbladder for storage. Bile contains cholesterol, water, salts like potassium and sodium, metals like copper, bile salts, and bilirubin (a yellow pigment produced as a result of red blood cell breakdown). Bile helps in the digestion of food by breaking down fats into fatty acids. It is then carried to the digestive tract to help in further digestion. The liver is the only organ in the human body that can regrow from its remaining part after surgery or damage to the liver. The diseases of the liver are called hepatic diseases, and the problems in the liver due to any external or internal factor are called hepatic disorders.

What Is Hepatic Circulation?

Hepatic circulation or liver blood flow is a vascular system that supplies blood to the liver. The liver unlike other organs has two blood supplies. One from the hepatic artery and the other from the portal vein.

What Is Hepatic Artery?

The hepatic artery is a blood vessel that supplies nutrients and oxygenated blood (pure or oxygen-rich blood) to the liver, pancreas, and the duodenum (first part of the small intestine). The hepatic artery enters the liver at the hilum along with the portal vein and efferent autonomic nerves (supply motor impulse to the heart muscle, smooth muscle, and glandular epithelium). A motor impulse is a physical response to a stimulus. The liver is a rough triangle in shape and has four parts or lobes, the right larger lobe, the left lobe, the small caudate lobe, and the quadrate lobe. The quadrate lobe and caudate are separated by porta hepatis or liver hilus. The hepatic artery has two branches, the right and left branches.

What Are Hepatic Artery Dysfunctions?

• Hepatic Artery Aneurysm: Hepatic aneurysm is a bulge in the wall of the blood vessel that is filled with blood.

• Hepatic Artery Stenosis: Hepatic artery stenosis commonly occurs after a liver transplant. Hepatic artery stenosis is the narrowing of the hepatic artery.

• Hepatic Infarction: Hepatic infarct is the death of tissue due to loss of blood supply. But this scenario is rare as the liver has two blood supplies.

What Is A Portal Vein?

A portal vein is the main blood vessel that carries blood from the pancreas, spleen, gastrointestinal tract, and gallbladder to the liver. The portal vein accesses the hilum and inserts into the liver. The portal vein separates from the right and left veins before entering the liver. The blood from other parts is brought here, and the liver removes toxic or harmful substances and processes the nutrients that are easy for the body to absorb. Then this purified blood is distributed into the circulation.

What Are Portal Vein Dysfunction?

• Portal Vein Thrombosis: It is narrowing or blockage in the portal vein due to a blood clot.

• Portal Vein Hypertension: Portal hypertension is the increase in the pressure inside the portal vein.

Why Is Hepatic Circulation Important?

The hepatic circulation is important because it plays an important role in digestion and absorption. The blood from the digestive tract and spleen comes to the liver, and the liver processes the nutrients from the food for the body for easy absorption.

What Are the Symptoms of Hepatic Circulation Disorder?

• Yellowish discoloration of the skin and eyes.

• Enlarged stomach due to excess fluid accumulation.

• Weakness and feeling tired.

• Visibly enlarged veins in the stomach.

• Enlarged liver and spleen.

• Vomiting.

What Is Hepatic Circulation Dysfunction?

• Obstruction to Hepatic Vascular Inflow: This obstruction includes,

  • Portal Vein Thrombosis: It is the narrowing or block in the hepatic artery by a block.

  • Hepatic Artery Thrombosis: It is the blood clot in the hepatic artery.

  • Presinusoidal Causes of Vascular Obstruction: It is the pathological increase in the blood pressure in the portal vein.

    • Sinusoids are irregular tubular structures for blood circulation. These act as blood capillaries in the liver. Presinusoidal is in front of the sinusoid.

• Obstruction to Blood Flow Through the Liver: This type includes,

  • Sickle Cell Disease: It is an inherited (runs in the family) blood disorder of red blood cells. Red blood cells are a component of the blood that transports oxygen to all other parts. The red blood cells are usually round, but in sickle cell disease, the red blood cells are hardened, become sticky, and are “C” shaped or take the shape of a tool called “sickle.” Hence the name sickle cell disease.

  • Disseminated Intravascular Coagulation: In this condition, the protein called fibrinogen which controls blood clotting becomes overactive. This results in abnormal thick blood clot formation inside the blood vessels.

  • Tumor: A bone marrow malignancy (cancerous tumor) also obstructs blood flow through the liver.

  • Infection: Bacterial or viral infections can obstruct blood flow.

• Obstruction to Hepatic Vascular Outflow: This type includes,

  • Macroscopic Hepatic Venous Thrombosis: It is usually caused by hepatocellular carcinoma (cancerous tumor in the liver).

  • Thrombosis of the Retrohepatic Inferior Vena Cava: A block in the inferior vena cava (it is a large blood vessel that carries deoxygenated blood from the abdomen and lower limbs to the heart).

  • Veno Occlusive Disease: It is a clinical syndrome that causes enlargement of the liver, enlargement of the stomach due to excess fluid accumulation, weight gain, and jaundice. It is caused due to stem cell transplantation.

How Are Hepatic Circulation Disorders Found?

• Physical Examination: Physical examination is done by the physician to check for ascites and look for dilated veins in the abdomen and anus.

• X-Rays: High-energy electromagnetic radiation is used to capture images of the internal tissues, bones, and organs.

• Doppler Ultrasound: A Doppler ultrasound uses high-frequency sound waves, and a small device called a transducer to detect the blood flow in blood vessels. A normal ultrasound does not show the blood flow in veins.

• CT Angiography: A CT angiography uses a combination of a CT scan and a special dye injected into the veins to detect the blood flow in a vein.

• Magnetic Resonance Angiography: Magnetic resonance angiography uses a combination of high-frequency radio waves in a magnetic field to capture images of the blood flow through the blood vessels.

• Endoscopy: Endoscopy is a procedure where a flexible tube with a light and camera is inserted through the mouth into the abdominal cavity to view the internal structures that display on a monitor.

How Is Hepatic Circulation Dysfunction Treated?

The treatment depends on the causes of the obstruction.

1. Surgery: Surgical removal if the blockage is due to a tumor or a large blood clot.

2. Medications: Medications like blood thinners if the block is due to a blood clot.

3. Diet: A low-sodium diet will be recommended.

4. Shunting: This procedure involves placing a stent to open the narrowed blood vessel and improve blood flow.

5. Liver Transplant: In liver failure cases, a liver transplant will be considered.

What Are the Complications of Hepatic Circulation Dysfunction?

• Ascites (excess fluid accumulation in the stomach).

• Variceal bleeding (varices are enlargement of blood vessels).

• Encephalopathy (damage to brain cells that results in various symptoms like confusion, disorientation, and altered mental state).

• Liver failure (the liver does not function properly, like not removing harmful substances from the blood or does not absorb essential nutrients from the blood).

Conclusion:

The hepatic circulation is an important system as it plays an important role in digestion and removal of toxic wastes from our body. The liver has two blood supplies, one from the hepatic artery and another from the portal vein. The hepatic artery transports blood to the liver, pancreas, and duodenum (the first part of the small intestine). The portal vein transfers blood from the gastrointestinal tract, pancreas, gallbladders, and spleen into the liver for purification. The liver removes the toxic wastes that result from processing medications and medications. The liver absorbs nutrients from the hepatic arterial supply. Any abnormality in the arterial or venous system can result in liver dysfunction. If the defect is not detected or treated early, liver failure may occur. Since hepatic circulation is important, having a healthy lifestyle and regular check-ups with the doctor can help detect the defect early, and with appropriate treatment, the lifespan can be increased.