Portal vein circulation

Eva Rudolf-Müller is a freelance writer in the medical team. She studied human medicine and newspaper sciences and has repeatedly worked in both areas - as a doctor in the clinic, as a reviewer, and as a medical journalist for various specialist journals. She is currently working in online journalism, where a wide range of medicine is offered to everyone.

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The venous circulation of the stomach, intestines, spleen and pancreas is called the portal vein circulation. The blood from these organs is first conducted to the liver via the portal vein (vena portae) and then fed to the right atrium via the inferior vena cava (inferior vena cava). Read everything you need to know about the portal circulation!

What is the portal vein circuit?

The portal vein circuit is part of the great bloodstream. All nutrients that are absorbed (reabsorbed) into the blood in the course of digestion in the small intestine and the upper part of the large intestine do not reach the heart directly via the veins of the great circulatory system, but are first supplied to the heart via the portal vein system (a vein that is located in Capillary areas) into the liver and only then into the inferior vena cava and further into the right atrium. The reason is that the liver is the central metabolic organ: When the blood flows through the capillary network of the liver, the substances absorbed in the intestine can be used immediately - they are stored, converted or broken down as required.

The liver also has an important detoxification function: toxins, alcohol and toxic metabolic products ingested with food are filtered out of the blood by the liver and rendered harmless. The liver also takes care of degradation substances from the spleen, which are also transported via the portal vein (such as bilirubin, the degradation product of the red blood pigment).

After their absorption in the digestive tract, various drugs are first brought into the liver via the portal vein circulation. Some of the active ingredients are metabolized here and only the rest of them pass through the bloodstream and can be distributed in the body and develop its effect (first-pass effect). In order to bypass the portal vein circulation and thus this first-pass effect, some drugs are therefore introduced directly into the bloodstream (as an infusion or injection).

The portal vein circulation also uses the bile produced in the liver: It reaches the gallbladder (storage location) via the bile ducts and continues into the intestine, where it supports fat digestion. A large part of the bile is later absorbed into the blood again via the intestinal wall and brought back to the liver via the portal vein (enterohepatic circulation).

Problems in the area of ​​the portal circulation

An increased pressure in the portal vein circulation caused by blood backlog is referred to as portal hypertension. The reason for the congestion can be in front of the liver (pre-hepatic), in the liver (intrahepatic) or after the liver (posthepatic). A prehepatic cause would be a portal vein thrombosis, i.e. the formation of a blood clot in the portal vein. Possible intrahepatic causes include acute or chronic inflammation of the liver (hepatitis), liver cirrhosis, liver tumors and sarcoid. The posthepatic causes of blood backlog and thus an increase in pressure in the portal vein circulation include heart diseases such as right heart failure or the "armored heart" (pericarditis constrictiva).

As a result of the disturbed blood flow in portal vein hypertension, a bypass circuit can develop: the blood in the portal vein then has to find its way through other veins to the inferior vena cava and back to the heart. The corresponding alternative veins can "wear out" and expand due to the additional load. For example, varicose veins can develop in the esophagus (esophageal varices) if the "diversion" takes place via the veins of the stomach and esophagus. Hemorrhoids are also in some cases the result of congestion in the portal vein circulation.

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