home Drugs What is portacaval anastomosis of the liver. Portal vein: functions, structure of the portal circulatory system, diseases and diagnosis Video: incomplete thrombosis of the portal vein on ultrasound

What is portacaval anastomosis of the liver. Portal vein: functions, structure of the portal circulatory system, diseases and diagnosis Video: incomplete thrombosis of the portal vein on ultrasound

Rice. 1. Topography of the liver; 1 - hepar; 2 - lig. falciforme hepatis; 3 - ventriculus; 4 - lien; 5 - colon transversum; 6 - lig. hepatogastricum.

The weight of a human liver reaches 1.5 kg, its consistency is soft, its color is reddish-brown, and its shape resembles a large shell. The convex diaphragmatic surface of the liver (facies diaphragmatica) faces upward and posteriorly. Anteriorly and especially to the left, the liver becomes thinner (Fig. 1 and 2). The lower visceral surface (facies visceralis) is concave. The liver occupies the right hypochondrium and extends through the epigastric region into the left hypochondrium. The anterior pointed edge of the liver usually does not extend from under the right costal arch to the outer edge of the right rectus abdominis muscle. Next, the lower border of the liver passes obliquely to the junction of the cartilages of the VII and VIII left ribs. The liver occupies almost the entire dome of the diaphragm. On the left it comes into contact with the stomach, below - with the right kidney, with the transverse colon and duodenum.

Rice. 2. Liver (top): 1 - lis. triangulare deist.; 2 - diaphragm; 3 - lig. coronarium hepatis; 4 - lig. triangulare sin.; 5 - appendix fibrosa hepatis; 6 - lobus sin. hepatis; 7 - lig. falciforme hepatis; 8 - lig. teres hepatis; 9 - incisura lig. teretis; 10 - margo inf.; 11 - vesica fellea (fundus); 12 - lobus dext. hepatis.
Rice. 3. Liver (back): 1 - lig. triangulare sin.; 2 - impressio gastrica; 3 - lig. coronarium hepatis; 4 - impressio oesophagea; 5 - lig. venosum hepatis; 6 - lobus caudatus hepatis; 7 - lig. falciforme hepatis; 8 - v. hepatica; 9 - lobus dext. hepatis; 10 - v. cava inf.; 11 - lig. v. cavae; 12 - facies diaphragmatica; 13 - impressio suprarenalis; 14 - processus caudatus; 13 - collum vesicae felleae; 16 - lig. triangulare dext.; 17 - impressio renalis; 18 - impressio colica; 19 - impressio duodenalis; 20 - vesica fellea; 21 - ductus choledochus; 22 - v. portae; 23 - lobus quadratus; 24 - lig. falciforme hepatis; 26 - a. hepatica propria; 26 - lig. teres hepatis; 27 - porta hepatis; 28 - tuber omentale; 29 - lobus sin.; 30 - appendix fibrosa hepatis.

The liver, with the exception of the upper-posterior surface attached to the diaphragm, is covered with peritoneum. The transition of the peritoneum from the diaphragm to the liver along the frontal plane is designated as the coronary ligament (lig. coronarium hepatis), the transition along the sagittal plane is designated as the falciform ligament (lig. falciforme hepatis), dividing the diaphragmatic surface of the liver into the right and left lobes (lobus hepatis dexter et sinister ). The visceral surface is divided into right, left, caudate (lobus caudatus) and square (lobus quadratus) lobes by two longitudinal grooves and one transverse one (porta of the liver). The gallbladder (see) is placed in the recess of the right longitudinal groove in front, and the inferior vena cava in the back. The left longitudinal groove includes the round ligament of the liver (lig. teres hepatis), formed from the neglected umbilical vein. Here it passes into the venous ligament (lig. venosum) - the remnant of the overgrown ductus venosus. Under the peritoneum on top of the liver there is a connective tissue capsule.

The portal vein (see) and the hepatic artery entering the gate of the liver and the lymphatic vessels and bile duct exiting the gate (Fig. 3) are covered with layers of peritoneum that make up the hepatoduodenal ligament (lig. hepatoduodenal). Its continuation is the hepatogastric ligament (lig. hepatogastricum) - the lesser omentum. A sheet of peritoneum stretches down to the right kidney from the liver - the hepatorenal ligament (lig. hepatorenale). Between the liver and the diaphragm on the sides of the falciform ligament, the right and left hepatic bursae (bursa hepatica dext. et sin.) are distinguished; between the liver and the stomach behind the lesser omentum is the omental bursa (bursa omentalis). Liver segments are shown in Fig.

The main segments of the liver: I - anterior segment: II - posterior segment; III - medial segment; IV - lateral segment. 1 - ductus cholcdoclius; 2 - v. portae; 3 - a. hepatica.

Rice. 4. Scheme of the structure of the lymphatic vessels of the liver: 1 - retrosternal lymph nodes; 2 - anterior group of diaphragmatic nodes; 3 - posterior group of diaphragmatic nodes; 4 - inferior vena cava; 5 - inferior phrenic artery; b - thoracic aorta; 7 - celiac lymph nodes; 8 - hepatic veins; 9 - hepatic lymph nodes; 10 - deep lymphatic vessels; 11 - superficial lymphatic vessels; 12 - diaphragm.

The bloodstream of the liver consists of the intraorgan part of the venous portal system, the drainage system of the hepatic veins and the system of hepatic arteries. Arterial blood supply to the liver is carried out by the hepatic artery (from the celiac artery system), which, entering the portal of the liver, is divided into right and left branches. Often there are accessory hepatic arteries coming from the branches of the celiac artery and from the superior mesenteric artery. The portal vein brings the bulk of blood to the liver. It is divided into lobar veins, from which segmental veins originate. Continuing to divide, the branches of the portal vein first become interlobular, and then thin septal venules, turning into capillaries - sinusoids of the lobule. The septal arterioles also open here, completing the branching of the segmental intrahepatic arteries. Thus, mixed blood flows through the sinusoids. Sinusoids are equipped with devices to regulate blood flow. As a result of the fusion of sinusoids, the central veins of the lobules are formed, from which blood flows first into the sublobular, and then into the collecting veins and, finally, into 3-4 hepatic veins. The latter open into the inferior vena cava. The lymphatic system of the liver (Fig. 4) begins with perilobular and superficial networks of capillaries, folding into superficial and deep lymphatic vessels, through which lymph flows either to the lymph nodes at the porta hepatis, or to the subphrenic nodes around the inferior vena cava. The vagus nerves and branches of the solar plexus take part in the innervation of the liver, thanks to which autonomic and afferent innervation is provided.

Blood supply to the liver

The blood supply to the liver is carried out by a system of arteries and veins, which are connected to each other and to the vessels of other organs. This organ performs a huge number of functions, including the detoxification of toxins, the synthesis of proteins and bile, and the storage of many compounds. Under conditions of normal blood circulation, it does its job, which has a positive effect on the condition of the whole organism.

How do blood circulation processes occur in the liver?

The liver is a parenchymal organ, that is, it does not have a cavity. Its structural unit is a lobule, which is formed by specific cells, or hepatocytes. The lobule has the shape of a prism, and neighboring lobules are combined into lobes of the liver. The blood supply to each structural unit is carried out using the hepatic triad, which consists of three structures:

Main arteries of the liver

Arterial blood enters the liver from vessels that originate from the abdominal aorta. The main artery of the organ is the hepatic one. Along its length, it gives blood to the stomach and gall bladder, and before entering the gate of the liver or directly in this area, it is divided into 2 branches:

the left hepatic artery, which carries blood to the left, quadrate and caudal lobes of the organ;
the right hepatic artery, which supplies blood to the right lobe of the organ and also gives off a branch to the gallbladder.

The arterial system of the liver has collaterals, that is, areas where neighboring vessels are united through collaterals. These may be extrahepatic or intraorgan associations.

Large and small veins and arteries take part in the blood circulation of the liver

Veins of the liver

The veins of the liver are usually divided into afferent and efferent. Along the afferent tract, blood moves to the organ, and along the efferent tract, it moves away from it and carries away the final products of metabolism. Several main vessels are associated with this organ:

portal vein - an afferent vessel that is formed from the splenic and superior mesenteric veins;
hepatic veins are a system of drainage tracts.

The portal vein carries blood from the organs of the digestive tract (stomach, intestines, spleen and pancreas). It is saturated with toxic metabolic products, and their neutralization occurs in the liver cells. After these processes, the blood leaves the organ through the hepatic veins, and then participates in the systemic circulation.

Diagram of blood circulation in the liver lobules

The topography of the liver is represented by small lobules, which are surrounded by a network of small vessels. They have structural features that help cleanse the blood of toxic substances. When entering the portal of the liver, the main afferent vessels are divided into small branches:

equity,
segmental,
interlobular,
intralobular capillaries.

These vessels have a very thin muscle layer to facilitate blood filtration. At the very center of each lobule, the capillaries merge into a central vein, which is devoid of muscle tissue. It flows into the interlobular vessels, and they, accordingly, into the segmental and lobar collecting vessels. Leaving the organ, the blood is distributed through 3 or 4 hepatic veins. These structures already have a full muscle layer and carry blood into the inferior vena cava, from where it enters the right atrium.

Portal vein anastomoses

The blood supply to the liver is adapted to ensure that the blood from the digestive tract is cleared of metabolic products, poisons and toxins. For this reason, stagnation of venous blood is dangerous for the body - if it collects in the lumen of blood vessels, toxic substances will poison the person.

Anastomoses are bypass routes for venous blood. The portal vein is connected to the vessels of some organs:

If for some reason the fluid cannot enter the liver (due to thrombosis or inflammatory diseases of the hepatobiliary tract), it does not accumulate in the vessels, but continues to move along bypass routes. However, this condition is also dangerous because the blood does not have the opportunity to get rid of toxins and flows into the heart in an unclean form. Portal vein anastomoses begin to function fully only in pathological conditions. For example, with cirrhosis of the liver, one of the symptoms is the filling of the veins of the anterior abdominal wall near the navel.

The most important processes occur at the level of liver lobules and hepatocytes

Regulation of blood circulation processes in the liver

The movement of fluid through the vessels occurs due to the pressure difference. The liver constantly contains at least 1.5 liters of blood, which moves through large and small arteries and veins. The essence of blood circulation regulation is to maintain a constant amount of fluid and ensure its flow through the vessels.

Mechanisms of myogenic regulation

Myogenic (muscular) regulation is possible due to the presence of valves in the muscular wall of blood vessels. When muscles contract, the lumen of the blood vessels narrows and fluid pressure increases. When they relax, the opposite effect occurs. This mechanism plays a major role in the regulation of blood circulation and is used to maintain constant pressure in different conditions: during rest and physical activity, in heat and cold, with increases and decreases in atmospheric pressure and in other situations.

Humoral regulation

Humoral regulation is the effect of hormones on the condition of the walls of blood vessels. Some of the biological fluids can affect veins and arteries, expanding or narrowing their lumen:

adrenaline - binds to adrenergic receptors in the muscular wall of intrahepatic vessels, relaxes them and provokes a decrease in blood pressure;
norepinephrine, angiotensin - act on veins and arteries, increasing fluid pressure in their lumen;
acetylcholine, products of metabolic processes and tissue hormones - simultaneously dilates arteries and constricts veins;
some other hormones (thyroxine, insulin, steroids) - provoke an acceleration of blood circulation and at the same time a slowdown in blood flow through the arteries.

Hormonal regulation underlies the response to many environmental factors. The secretion of these substances is carried out by endocrine organs.

Nervous regulation

Mechanisms of nervous regulation are possible due to the peculiarities of the innervation of the liver, but they play a secondary role. The only way to influence the condition of the hepatic vessels through the nerves is to irritate the branches of the celiac nerve plexus. As a result, the lumen of the vessels narrows, the amount of blood flow decreases.

Blood circulation in the liver differs from the usual pattern that is typical for other organs. The inflow of fluid is carried out by veins and arteries, and the outflow is carried out by the hepatic veins. During circulation in the liver, the fluid is cleared of toxins and harmful metabolites, after which it enters the heart and further participates in blood circulation.

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Blood supply to the liver diagram

The liver has a dual blood supply: approximately 70% of the blood comes from the portal vein, the rest from the hepatic artery. The branches of the hepatic vein drain blood into the inferior vena cava. The functioning of the liver is based on the complex interaction of these vessels.

Depending on the course of the vessels, the liver is divided into eight segments, which is of great importance from a surgical point of view, since when choosing the type of surgical intervention, preference is often given to segmentectomy rather than lobectomy.

Segment 1 (caudal lobe) is autonomous, since it is supplied with blood from both the left and right branches of the portal vein and from the hepatic artery, while the venous outflow from this segment is carried out directly into the inferior vena cava. In Budd-Chiari syndrome, thrombosis of the main hepatic vein leads to the fact that the outflow of blood from the liver occurs entirely through the caudate lobe, which is significantly hypertrophied.

The liver is clearly visible on a plain abdominal radiograph. An appendage of the right lobe is often found, directed towards the region of the right iliac fossa - the so-called Riedel's lobe.

View of the liver from the front and bottom, showing the division into 8 segments. Segment 1 - caudate lobe. Computed tomography of the liver. An axial view through the superior fornix of the liver allows one to see the division of the hepatic parenchyma into segments.

The posterior segment of the right lobe is rarely viewed at this level, since the bulk of this segment lies below the anterior segment of the right lobe:

1 - medial segment of the left lobe of the liver; 2 - left hepatic vein; 3 - lateral segment of the left lobe of the liver;

4 - median hepatic vein; 5 - anterior segment of the right lobe of the liver; 6 - posterior segment of the right lobe of the liver;

7 - right hepatic vein; 8 - aorta; 9 - esophagus;

10 - stomach; 11 - spleen. Budd-Chiari syndrome: decreased absorption of colloid in the liver in the caudate lobe of the liver and increased absorption in the bones and spleen.

Scintigraphy using technetium. Normal abdominal radiograph showing Riedel's lobe in the right hypochondrium

The hepatic artery, portal vein and common hepatic duct are located nearby at the porta hepatis. The hepatic artery is normally a branch of the celiac trunk, while the gallbladder is supplied with blood from the cystic artery; Anatomical features of the structure of these vessels are often encountered.

There are several ways to contrast the portal vein, which forms at the confluence of the splenic and superior mesenteric veins behind the head of the pancreas.

1 - portal vein; 2 - hepatic artery; 3 - celiac trunk;

4 - aorta; 5 - splenic vein; 6 - gastroduodenal artery;

7 - superior mesenteric vein; 8 - common bile duct; 9 - gallbladder;

10 - cystic artery; 11 - hepatic ducts

The method of direct percutaneous injection into the splenic pulp (splenovenography) used to be common, but is now rarely used, even with an enlarged spleen and signs of portal hypertension. In infants with an open umbilical vein, direct catheterization with contrast of the left portal vein system is possible. Currently, selective angiography is more often used, when the portal system is visualized during catheterization of the splenic artery and subsequent observation of the venous return phase after the passage of contrast through the spleen.

In patients with portal hypertension, image quality may be poor due to hemodilution and decreased contrast agent concentrations, which can be corrected by digital subtraction angiography. Once the catheter has passed through the right atrium and ventricle, it can be inserted into the hepatic veins. In this case, it is easy to evaluate the X-ray image and measure venous pressure, for which the value of free hepatic venous pressure in the lumen of the vessel is first recorded, then the catheter is carefully immersed in the hepatic parenchyma.

The tip of the balloon expands, and the measured value (fixed hepatic venous pressure) practically corresponds to the pressure in the portal vein, which allows the gradient of this parameter to be calculated. It is easiest to pass the catheter through the right internal jugular vein, since this provides almost straight-line access. A similar access technique is used for transvenous liver biopsy.

Using ultrasound of a normal liver, its size and consistency, filling defects, anatomy of the bile duct system and portal vein are assessed. The hepatic parenchyma and surrounding tissues can also be examined using computed tomography.

Ultrasound examination of anatomical structures at the porta hepatis.

The hepatic artery is located between the dilated common hepatic duct and the portal vein.

For magnetic resonance cholangiopancreatography, T1 and T2 relaxation times of the medium are used. The fluid signal has very low density (producing a dark color) on T2 images and high density (producing a light color) on T2 images. With this research method, T2 images are used to obtain cholangiograms and pancreatograms. The sensitivity and specificity of the technique vary depending on the technique and indication.

If the suspicion of pathology is small, it is better to perform magnetic resonance cholangio- and pancreatography, and if there is a high probability of surgical intervention, prefer endoscopic retrograde cholangiography. In addition, periampullary formations often go undetected due to artifacts caused by the accumulation of air in the duodenum. Unfortunately, magnetic resonance imaging is not sensitive enough for early diagnosis of bile duct pathology, for example in the case of subtle lesions often found in primary sclerosing cholangitis. The TESLA scanning method is rarely used to visualize the bile ducts.

Computer or MRI are the best methods for studying liver pathology. Thanks to contrast and imaging in the arterial and venous phases, it is possible to diagnose both benign and malignant formations. 3D computer and MRI provide images of blood vessels. With the additional use of MRC or TESLA images, biliary tract cancer can be diagnosed.

a - Magnetic resonance imaging showing a normal portal vein system. The superior mesenteric vein (shown by a short arrow) and its main branches are visible.

The portal vein (long arrow) passes further into the liver. The right lobe of the liver (R) has been identified.

b,c - On the magnetic resonance imaging (b) in the middle sagittal projection, the aorta (shown by a long arrow), the celiac trunk (short arrow) and the root of the superior mesenteric artery (arrowhead) are identified.

Contributed by Dr. Drew Torigian. TESLA scanning (c) also serves as a non-invasive method for studying the anatomy of the biliary tract:

RHD - right hepatic duct; LHD - left hepatic duct; CHD - common hepatic duct; 1 - “cystic duct” - cystic duct.

Computer or MRI can be used as the only research methods to detect tumors, describe vascular anatomy and determine the extent of bile duct damage.

Isotope scanning of the liver and spleen using 99mTc (a). HIDA scan showing normal absorption and excretion of the compound into the bile duct (b).

The study can be performed in conjunction with cholecystokinin stimulation to assess gallbladder or sphincter of Oddi dysfunction.

1 - surface markers of the chest; 2 - liver; 3 - spleen

The radioisotope method for studying the liver is currently used much less frequently. This research method determines the concentration of technetium in reticuloendotheliocytes (Kupffer cells) administered intravenously.

The laparoscopic method is rarely used for direct visual examination of the liver, but it allows biopsy to be performed under visual control, since in this case the lower surface of the organ is clearly visible.

Educational video segmental structure of the liver in the diagram

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How is the blood supply to the liver structures?

The liver plays one of the main roles in metabolism. The ability to perform its functions, in particular neutralization, directly depends on how blood flows through it.

The peculiarity of the blood supply to the liver, unlike other internal organs, is that in addition to arterial blood saturated with oxygen, it also receives venous blood rich in valuable substances.

The structural unit of the liver is a lobe, which has the shape of a faceted prism, in which hepatocytes are located in rows. Each lobule is approached by a vascular triad of interlobular vein, artery and bile duct, which are also accompanied by lymphatic vessels. The blood supply to the lobules is divided into 3 channels:

Influx to the lobules.
Circulation inside the lobules.
Outflow from the hepatic lobules.

Blood sources

Arterial (about 30%) comes from the abdominal aorta via the hepatic artery. It is necessary for the normal functioning of the liver and to perform complex functions.

At the porta hepatis, the artery divides into two branches: the one going to the left supplies the left lobe, and the one going to the right supplies the right lobe.

From the right one, which is larger, a branch goes to the gall bladder. Sometimes a branch extends from the hepatic artery to the quadrate lobe.

Venous (about 70%) enters through the portal vein, which is collected from the small intestine, colon, rectum, stomach, pancreas, and spleen. This explains the biological role of the liver for humans: hazardous substances, poisons, medications, and processed products come from the intestines for neutralization and decontamination.

What is the blood supply algorithm?

Both sources of venous and arterial blood enter the organ through the gates of the liver, then they branch greatly, dividing into:

All these vessels have a thin muscle layer.

Penetrating into the lobule, the interlobular artery and vein merge into a single capillary network running along the hepatocytes to the central part of the lobule. In the center of the lobule, the capillaries gather into the central vein (it is devoid of a muscle layer). The central vein then flows into the interlobular, segmental, and lobar collecting vessels, forming 3–4 hepatic veins at the outlet at the hilum. They already have a good muscle layer, flow into the inferior vena cava, and it, in turn, enters the right atrium.

In general, the blood supply in the hepatic lobule can be displayed as follows:

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B→ K → Cv A→, where B and A are the interlobular artery and vein, K is the capillary, Cv is the central vein of the lobule.

Anastomoses

The portal vein has numerous connections (anastomoses) with other organs. This is necessary for extreme necessity: if there are disturbances in the liver, and due to high pressure resistance, blood cannot flow there, through anastomoses it goes into the venous bed of these organs and thus does not stagnate, but enters the heart, although it never purified.

The portal vein has anastomoses with:

Stomach.
The anterior wall of the abdomen and the veins located near the navel.
Esophagus.
Veins of the rectum.
Inferior vena cava.

Therefore, if a clear venous pattern in the form of a jellyfish appears on the abdomen, dilated veins are found during examination of the esophagus and rectum, we can safely say that the anastomoses are working in an enhanced mode, and in the portal vein the increased pressure prevents the passage of blood.

Blood pressure increases with cirrhosis and other diseases; this condition is called portal hypertension.

Regulation of blood supply

The liver normally contains about half a liter of blood. Its advancement is carried out due to the pressure difference: it comes from the arteries under a pressure of at least 110 mm. rt. st, which in the capillary network is reduced to 10 mm. rt. Art., in the portal veins it is within 5, and in the collecting venules it can even be 0.

Normal functioning of the organ requires constant maintenance of blood volume. To do this, the body has 3 types of regulation, which work thanks to the valve system of veins.

Myogenic regulation

Muscular regulation is most important because it is automatic. When muscles contract, they narrow the lumen of the vessel, and when they relax, they expand.

The structure of the walls of blood vessels

Thus, they regulate the constancy of blood supply under the influence of various factors: physical activity, during rest, pressure fluctuations, and diseases.

Humoral regulation

Carried out with the help of hormones:

Adrenalin. Produced during stress, it enters the blood and acts on the alpha-adrenergic receptors of the portal vein, causing its narrowing.

In small arterial vessels of the parenchyma, it acts on beta-adrenergic receptors and dilates intrahepatic vessels.

Norepinephrine and angiotensin. They affect both the venous and arterial systems equally, leading to a narrowing of all vessels, resulting in a decrease in the amount of blood supplied to the liver.

Acetylcholine. Dilates arterial vessels, which means improves blood supply to the liver. But it narrows the venules, i.e. prevents blood from flowing out of the organ. As a result, the blood is deposited in the liver.

Other hormones, such as thyroxine, glucocorticoids, insulin and glucagon, increase metabolic processes, which increases blood flow. Metabolites produced in tissues (histamine, prostaglandin, carbon dioxide) reduce portal inflow, but increase arterial blood flow.

Nervous regulation

It is slightly expressed, therefore it plays a minor role in the regulation of blood circulation.

Sympathetic innervation. Carried out by branches from the celiac plexus. Causes vasoconstriction, which reduces blood flow.
Parasympathetic. Comes from the vagus nerve (X pair). Has no effect.

An important indicator of impaired hepatic circulation is congested veins of the anastomoses.
Liver recovery occurs extremely slowly, and poor circulation only aggravates the situation.
The altered hormonal background of a person with diabetes mellitus, diseases of the thyroid gland and adrenal glands can make changes in the portal circulation.

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Features of blood supply to the liver

Features of the liver circulatory system

The liver plays a major role in metabolic processes occurring in the body. The quality of an organ’s functions depends on its blood supply. The liver tissues are enriched with blood from the artery, which is saturated with oxygen and nutrients. Valuable fluid enters the parenchyma from the celiac trunk. Venous blood, saturated with carbon dioxide and coming from the spleen and intestines, leaves the liver through the portal vessel.

The anatomy of the liver includes two structural units called lobules, which are similar to a faceted prism (the edges are created by rows of hepatocytes). Each lobule has a developed vascular network, consisting of an interlobular vein, artery, bile duct, and lymphatic vessels. The structure of each lobule suggests the presence of 3 blood streams:

for the flow of blood serum to the lobules;
for microcirculation inside the structural unit;
to drain blood from the liver.

25-30% of the blood volume circulates through the arterial network under pressure up to 120 mmHg. Art., in the portal vessel - 70-75% (10-12 mm Hg). In sinusoids, the pressure does not exceed 3-5 mm Hg. Art., in the veins - 2-3 mm Hg. Art. If pressure increases, excess blood is released into the anastomoses between the vessels. After processing, arterial blood is directed into the capillary network, and then sequentially enters the hepatic vein system and accumulates in the lower hollow vessel.

The blood circulation rate in the liver is 100 ml/min, but with pathological dilatation of blood vessels due to their atony, this value can increase to 5000 ml/min. (about 3 times).

The interdependence of arteries and veins in the liver determines the stability of blood flow. When blood flow in the portal vein increases (for example, against the background of functional hyperemia of the gastrointestinal tract during digestion), the rate of movement of red liquid through the artery decreases. And, conversely, when the blood circulation rate in the vein decreases, perfusion in the artery increases.

The histology of the liver circulatory system suggests the presence of the following structural units:

main vessels: hepatic artery (with oxygenated blood) and portal vein (with blood from unpaired peritoneal organs);
an extensive network of vessels that flow into each other through lobar, segmental, interlobular, perilobular, capillary structures with a connection at the end into an intralobular sinusoidal capillary;
efferent vessel - collecting vein, which contains mixed blood from the sinusoidal capillary and directs it to the sublobular vein;
vena cava, designed to collect purified venous blood.

If for some reason blood cannot move at normal speed through the portal vein or artery, it is redirected to the anastomoses. A special feature of the structure of these structural elements is the ability to communicate with the blood supply system of the liver with other organs. True, in this case, the regulation of blood flow and redistribution of the red liquid is carried out without purifying it, so it, without lingering in the liver, immediately enters the heart.

The portal vein has anastomoses with the following organs:

stomach;
the anterior wall of the peritoneum through the periumbilical veins;
esophagus;
rectal section;
the lower part of the liver itself through the vena cava.

Consequently, if a distinct venous pattern appears on the abdomen, resembling the head of a jellyfish, varicose veins of the esophagus and rectum are detected, it should be stated that the anastomoses are working in an enhanced mode, and in the portal vein there is a strong excess of pressure that prevents the passage of blood.

Regulation of blood supply to the liver

The normal amount of blood in the liver is considered to be 1.5 liters. Blood circulation is carried out due to the difference in pressure in the arterial and venous group of vessels. To ensure stable blood supply to the organ and its proper functioning, there is a special system for regulating blood flow. To do this, there are 3 types of regulation of blood supply, working through a special valve system of veins.

Myogenic

This regulatory system is responsible for muscular contraction of the vascular walls. Due to muscle tone, the lumen of blood vessels, when they contract, narrows, and when they relax, they expand. With the help of this process, the pressure and speed of blood flow increases or decreases, that is, the stability of the blood supply is regulated under the influence of:

Excessive physical activity and pressure fluctuations negatively affect the tone of liver tissue.

exogenous factors such as physical activity, rest;
endogenous factors, for example, during pressure fluctuations, the development of various diseases.

Features of myogenic regulation:

ensuring a high degree of autoregulation of hepatic blood flow;
maintaining constant pressure in the sinusoids.

Humoral

Regulation of this type occurs through hormones, such as:

Hormonal imbalances can negatively impact liver function and integrity.

Adrenalin. It is produced during stress and affects the α-adrenergic receptors of the portal vessel, causing relaxation of the smooth muscles of the intrahepatic vascular walls and a decrease in pressure in the blood flow system.
Norepinephrine and angiotensin. They have the same effect on the venous and arterial systems, causing a narrowing of the lumen of their vessels, which leads to a decrease in the amount of blood entering the organ. The process is started by increasing vascular resistance in both channels (venous and arterial).
Acetylcholine. The hormone helps to expand the lumen of arterial vessels, which means it improves blood supply to the organ. But at the same time, a narrowing of the venules occurs, therefore, the outflow of blood from the liver is disrupted, which provokes the deposition of blood into the hepatic parenchyma and a jump in portal pressure.
Metabolic products and tissue hormones. Substances dilate arterioles and narrow portal venules. There is a decrease in venous circulation against the background of an increase in the flow rate of arterial blood with an increase in its total volume.
Other hormones - thyroxine, glucocorticoids, insulin, glucagon. The substances cause an increase in metabolic processes, while blood flow increases against the background of a decrease in portal inflow and an increase in arterial blood supply. There is a theory that adrenaline and tissue metabolites influence these hormones.

Nervous

The influence of this form of regulation is secondary. There are two types of regulation:

Sympathetic innervation, in which the process is controlled by the branches of the celiac plexus. The system leads to a narrowing of the lumen of blood vessels and a decrease in the amount of incoming blood.
Parasympathetic innervation, in which nerve impulses come from the vagus nerve. But these signals have no effect on the blood supply to the organ.

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Table of contents of the topic "Topographic anatomy of the liver.":

Portal vein, v. portae, also brings blood to the liver. It collects blood from all unpaired abdominal organs. Portal vein formed from the fusion of the superior mesenteric, v. mesenterica superior, and splenic, v. splenica (lienalis), veins. The place of their confluence, that is, the place of formation of v. portae. located behind the head of the pancreas.

They drain into the portal vein v. pancreaticoduodenalis superior, v. prepylorica and right and left gastric veins, vv. gastricae dextra et sinistra. The latter often flows into the splenic vein. Inferior mesenteric vein, v. mesenterica inferior, as a rule, flows into the splenic vein, less often into the superior mesenteric vein.

From under the head of the pancreas portal vein goes up behind the duodenum and enters the space between the layers of the hepatoduodenal ligament. There it is located behind the hepatic artery and common bile duct. The length of the portal vein ranges from 2 to 8 cm.

At a distance of 1.0-1.5 cm from porta hepatis or at the gate it divides into right and left branches, r. dexter et r. sinister.

Tumors of the pancreas, especially its head, can compress the pancreas lying posterior to the head portal vein, resulting in portal hypertension, that is, an increase in venous pressure in the portal vein system.

Outflow through the portal vein is also impaired in liver cirrhosis. A compensatory mechanism for impaired outflow becomes collateral blood flow through anastomoses with branches of the vena cava ( portocaval anastomoses).

Portocaval anastomoses are:
1) anastomoses between the veins of the stomach (system v. portae) and the veins of the esophagus (system v. cava superior);
2) anastomoses between the upper (v. portae) and middle (v. cava inferior) veins of the rectum;
3) between the umbilical veins (v. portae) and the veins of the anterior abdominal wall (v. cava superior and inferior);
4) anastomoses of the superior and inferior mesenteric, splenic veins (v. portae) with veins of the retroperitoneal space (renal, adrenal, testicular or ovarian veins and others flowing into v. cava inferior).

Hepatic veins

Hepatic veins,vv. hepaticae, drain blood from the liver. In most cases, there are three constantly occurring venous trunks: the right, intermediate and left hepatic veins. They flow into the inferior vena cava immediately below foramen v. cavae in the tendon part of the diaphragm. On the pars nuda of the posterior surface of the liver, a groove of the inferior vena cava, sulcus venae cavae, is formed.

The hepatic artery is a branch of the celiac trunk. It passes along the upper edge of the pancreas to the initial part of the duodenum, then goes up between the leaves of the lesser omentum, located in front of the portal vein and medial to the common bile duct, and at the porta hepatis it divides into right and left branches. Its branches also include the right gastric and gastroduodenal arteries. Additional branches are often found. Topographic anatomy has been carefully studied on donor livers. With abdominal trauma or catheterization of the hepatic artery, its dissection is possible. Embolization of the hepatic artery sometimes leads to the development of gangrenous cholecystitis.

Clinical manifestations

The diagnosis is rarely made while the patient is alive; There are few works describing the clinical picture. Clinical manifestations are associated with an underlying disease, for example, bacterial endocarditis, periarteritis nodosa, or are determined by the severity of upper abdominal surgery. Pain in the epigastric region on the right occurs suddenly and is accompanied by shock and hypotension. There is pain on palpation of the right upper quadrant of the abdomen and the edge of the liver. Jaundice increases rapidly. Typically, leukocytosis, fever, and biochemical blood tests reveal signs of cytolytic syndrome. Prothrombin time increases sharply, bleeding appears. When large branches of the artery are occluded, a coma develops and the patient dies within 10 days.

It is necessary to carry out hepatic arteriography. It can be used to detect hepatic artery obstruction. Intrahepatic collaterals develop in the portal and subcapsular areas. Extrahepatic collaterals with neighboring organs are formed in the ligamentous apparatus of the liver [3].

Scanning.Infarctions are usually round or oval, occasionally wedge-shaped, located in the center of the organ. In the early period, they are detected as hypoechoic foci during ultrasound examination (ultrasound) or poorly demarcated areas of reduced density on computed tomograms that do not change with the introduction of a contrast agent. Later, heart attacks look like confluent foci with clear boundaries. Magnetic resonance imaging (MRI) allows you to identify infarcts as areas with low signal intensity on T1-weighted images and with high intensity on T2-weighted images. With large infarcts, the formation of “lake” of bile, sometimes containing gas, is possible.

Treatment should be aimed at eliminating the cause of the damage. To prevent secondary infection during liver hypoxia, antibiotics are used. The main goal is the treatment of acute hepatocellular failure. In case of arterial injury, percutaneous embolization is used.

Damage to the hepatic artery during liver transplantation

When the bile ducts are damaged due to ischemia, they speak of ischemic cholangitis.It develops in patients who have undergone liver transplantation due to thrombosis or stenosis of the hepatic artery or occlusion of the paraductal arteries |8[. Diagnosis is complicated by the fact that the picture when examining biopsy specimens may indicate obstruction of the bile ducts without signs of ischemia.

After liver transplantation, hepatic artery thrombosis is detected using arteriography. Doppler examination does not always reveal changes; moreover, correct assessment of its results is difficult [b]. The high reliability of spiral CT has been shown.

Hepatic artery aneurysms

Hepatic artery aneurysms are rare and account for one fifth of all visceral vessel aneurysms. They may be a complication of bacterial endocarditis, periarteritis nodosa, or arteriosclerosis. Among the causes, the role of mechanical damage is increasing, for example due to road traffic accidents or medical interventions such as biliary tract surgery, liver biopsy and invasive X-ray examinations. False aneurysms occur in patients with chronic pancreatitis and pseudocyst formation. Hemobilia is often associated with false aneurysms. Aneurysms are congenital, intra- and extrahepatic, ranging in size from the head of a pin to a grapefruit. Aneurysms are identified by angiography or discovered incidentally during surgery or autopsy.

Clinical manifestations varied. Only a third of patients have the classic triad: jaundice |24|, abdominal pain and hemobilia. A common symptom is abdominal pain; the period from their appearance to the rupture of the aneurysm can reach 5 months.

In 60-80% of patients, the reason for the initial visit to the doctor is the rupture of a modified vessel with the leakage of blood into the abdominal cavity, biliary tract or gastrointestinal tract and the development of hemoperitoneum, hemobilia or hematemesis.

Ultrasound allows you to make a preliminary diagnosis; it is confirmed using hepatic arteriography and contrast-enhanced CT (see Fig. 11-2). Pulsed Doppler ultrasound can detect turbulence of blood flow in the aneurysm.

Treatment. For intrahepatic aneurysms, vessel embolization is used under angiography control (see Fig. 11-3 and 11-4). In patients with aneurysms of the common hepatic artery, surgical intervention is necessary. In this case, the artery is ligated above and below the site of the aneurysm.

Hepatic arteriovenous fistulas

Common causes of arteriovenous fistulas are blunt trauma to the abdomen, liver biopsy or tumors, usually primary liver cancer. Patients with hereditary hemorrhagic telangiectasia (Randu-Weber-Osler disease) have multiple fistulas, which can lead to congestive heart failure.

If the fistula is large, a murmur can be heard over the right upper quadrant of the abdomen. Hepatic arteriography can confirm the diagnosis. Embolization with gelatin foam is usually used as a therapeutic measure.

The enrichment of liver tissue occurs through two vessels: the artery and portal vein, which are branched in the left and right lobes of the organ. Both vessels enter the gland through the “gate” located at the bottom of the right lobe. The blood supply to the liver is distributed in the following percentage: 75% of the blood passes through the portal vein, and 25% through the artery. involves the passage of 1.5 liters of valuable fluid every 60 seconds. when the pressure in the portal vessel is up to 10-12 mm Hg. Art., in the artery - up to 120 mm Hg. Art.

The liver suffers greatly from a lack of blood supply, and with this, the entire human body.

Features of the liver circulatory system

for the flow of blood serum to the lobules;
for microcirculation inside the structural unit;
to drain blood from the liver.

25-30% of the blood volume circulates through the arterial network under pressure up to 120 mmHg. Art., in the portal vessel - 70-75% (10-12 mm Hg. Art.). In sinusoids, the pressure does not exceed 3-5 mm Hg. Art., in the veins - 2-3 mm Hg. Art. If pressure increases, excess blood is released into the anastomoses between the vessels. After processing, arterial blood is directed into the capillary network, and then sequentially enters the hepatic vein system and accumulates in the lower hollow vessel.

The blood circulation rate in the liver is 100 ml/min, but with pathological dilatation of blood vessels due to their atony, this value can increase to 5000 ml/min. (about 3 times).

The histology of the liver circulatory system suggests the presence of the following structural units:

main vessels: hepatic artery (with oxygenated blood) and portal vein (with blood from unpaired peritoneal organs);
an extensive network of vessels that flow into each other through lobar, segmental, interlobular, perilobular, capillary structures with a connection at the end into an intralobular sinusoidal capillary;
efferent vessel - collecting vein, which contains mixed blood from the sinusoidal capillary and directs it to the sublobular vein;
vena cava, designed to collect purified venous blood.

The portal vein has anastomoses with the following organs:

stomach;
the anterior wall of the peritoneum through the periumbilical veins;
esophagus;
rectal section;
the lower part of the liver itself through the vena cava.

Regulation of blood supply to the liver

Myogenic

Excessive physical activity and pressure fluctuations negatively affect the tone of liver tissue.

exogenous factors such as physical activity, rest;
endogenous factors, for example, during pressure fluctuations, the development of various diseases.

Features of myogenic regulation:

ensuring a high degree of autoregulation of hepatic blood flow;
maintaining constant pressure in the sinusoids.

Humoral

Regulation of this type occurs through hormones, such as:

Hormonal imbalances can negatively impact liver function and integrity.

Adrenalin. It is produced during stress and affects the α-adrenergic receptors of the portal vessel, causing relaxation of the smooth muscles of the intrahepatic vascular walls and a decrease in pressure in the blood flow system.
Norepinephrine and angiotensin. They have the same effect on the venous and arterial systems, causing a narrowing of the lumen of their vessels, which leads to a decrease in the amount of blood entering the organ. The process is started by increasing vascular resistance in both channels (venous and arterial).
Acetylcholine. The hormone helps to expand the lumen of arterial vessels, which means it improves blood supply to the organ. But at the same time, a narrowing of the venules occurs, therefore, the outflow of blood from the liver is disrupted, which provokes the deposition of blood into the hepatic parenchyma and a jump in portal pressure.
Metabolic products and tissue hormones. Substances dilate arterioles and narrow portal venules. There is a decrease in venous circulation against the background of an increase in the flow rate of arterial blood with an increase in its total volume.
Other hormones - thyroxine, glucocorticoids, insulin, glucagon. The substances cause an increase in metabolic processes, while blood flow increases against the background of a decrease in portal inflow and an increase in arterial blood supply. There is a theory that adrenaline and tissue metabolites influence these hormones.