Portal hypertension - Diagnosis

Visualization of the portal venous system

Non-invasive methods

Non-invasive methods of examination allow to determine the diameter of the portal vein, the presence and severity of collateral circulation. It is necessary to pay attention to the presence of any volumetric formations. The examination begins with the simplest methods - ultrasound and/or CT. Then, if necessary, resort to more complex methods of vascular visualization.

1. Ultrasound examination

It is necessary to examine the liver longitudinally, along the costal arch, and transversely, in the epigastric region. Normally, it is always possible to see the portal and superior mesenteric veins. It is more difficult to see the splenic vein.

If the portal vein is enlarged, portal hypertension may be suspected, but this is not a diagnostic sign. Detection of collaterals confirms the diagnosis of portal hypertension. Ultrasound allows for reliable diagnosis of portal vein thrombosis; in its lumen, areas of increased echogenicity caused by the presence of thrombi can sometimes be detected.

The advantage of ultrasound over CT is the ability to obtain any section of an organ.

Doppler ultrasound examination

Doppler ultrasound can reveal the structure of the portal vein and hepatic artery. The results of the study depend on careful analysis of image details, technical skills and experience. Difficulties arise when examining a small cirrhotic liver, as well as in obese individuals. The quality of visualization is improved by color Doppler mapping. Correctly performed Doppler ultrasound can diagnose portal vein obstruction as reliably as angiography.

Clinical significance of Doppler ultrasound

Portal vein

• Passability
• Hepatofugal blood flow
• Anatomical anomalies
• Patency of portosystemic shunts
• Acute circulatory disorders

Hepatic artery

• Patency (after transplantation)
• Anatomical anomalies

Hepatic veins

• Detection of Budd-Chiari syndrome

In 8.3% of cases of liver cirrhosis, Doppler ultrasound reveals hepatofugal blood flow through the portal, splenic and superior mesenteric veins. It corresponds to the severity of liver cirrhosis and the presence of signs of encephalopathy. Bleeding from varicose veins most often develops with hepatopetal blood flow.

Doppler ultrasound can detect abnormalities of the intrahepatic branches of the portal vein, which is important when planning surgical intervention.

Color Doppler mapping is useful for identifying portosystemic shunts, including those after transjugular intrahepatic portosystemic shunting with stents (TIPS), and the direction of blood flow through them. It can also identify natural intrahepatic portosystemic shunts|.

Color Doppler mapping is effective in diagnosing Budd-Chiari syndrome.

The hepatic artery is more difficult to detect than the hepatic vein due to its smaller diameter and length. However, duplex ultrasound is the main method for assessing the patency of the hepatic artery after liver transplantation.

Duplex ultrasound is used to determine portal blood flow. The average linear velocity of blood flow in the portal vein is multiplied by its cross-sectional area. Blood flow values obtained by different operators may differ. This method is more applicable to determining acute, significant changes in blood flow than to monitoring chronic changes in portal hemodynamics.

The portal vein blood flow velocity correlates with the presence of esophageal varices and their size. In cirrhosis, the portal vein blood flow velocity usually decreases; if its value is below 16 cm/s, the probability of portal hypertension development increases significantly. The portal vein diameter usually increases; in this case, the congestion index can be calculated, i.e. the ratio of the cross-sectional area of the portal vein to the average blood flow velocity through it. This index is increased in varicose veins and correlates with liver function.

Ultrasound signs of portal hypertension:

• an increase in the diameter of the portal and splenic veins and insufficient expansion of the portal vein during inhalation. The diameter of the portal vein on exhalation normally does not exceed 10 mm, on inhalation - 12 mm. If the diameter of the portal vein is more than 12 mm on exhalation and almost does not respond with an increase in diameter on inhalation - this is an undoubted sign of portal hypertension. The diameter of the splenic vein on exhalation is normally up to 5-8 mm, on inhalation - up to 10 mm. Expansion of the diameter of the splenic vein by more than 10 mm is a reliable sign of portal hypertension;
• an increase in the diameter of the superior mesenteric vein; normally its diameter on inhalation is up to 10 mm, on exhalation - up to 2-6 mm. An increase in the diameter of the superior mesenteric vein and the absence of its increase on inhalation is a more reliable sign of portal hypertension than an increase in the diameter of the portal and splenic veins;
• umbilical vein recanalization;
• portocaval and gastrorenal anastomoses are determined.

2. Splenomanometry is performed after puncture of the spleen with a 0.8 mm diameter needle, which is then connected to a water manometer.

Normally, the pressure does not exceed 120-150 mm Hg (8.5-10.7 mm Hg).

A pressure of 200-300 mm H2O indicates moderate portal hypertension, 300-500 mm H2O and higher indicates significant hypertension.

3. Hepatomanometry is performed after liver puncture, regardless of the position of the needle in the liver, the pressure near the sinusoids reflects the pressure in the portal system. Intrahepatic pressure is normally 80-130 mm H2O, with CP it increases 3-4 times.
4. Portomanometry - direct measurement of pressure in the portal system (portal vein) can be performed during laparotomy, as well as during transumbilical portography. In this case, a catheter is inserted through the bougienaged umbilical vein to the portal vein. Moderate portal hypertension (portal pressure 150-300 mm H2O) and severe portal hypertension (portal pressure above 300 mm H2O) are conventionally distinguished.
5. Portomanometry ends with portohepatography - a contrast agent is injected into the portal vein through a catheter, which allows one to make a judgment about the state of the vascular bed in the liver and the presence of an intrahepatic block.
6. Splenoportography is performed after splenomanometry, a contrast agent is injected into the spleen through a catheter. Splenoportography provides an idea of the state of the splenoportal bed: its patency, branching of the vessels of the portal vein system and liver, the presence of anastomoses between the veins of the spleen and diaphragm. In case of intrahepatic block, only the main trunks of the portal vein branching are visible on the splenoportogram. In case of extrahepatic block, splenoportography allows us to determine its location.
7. Hepatovenography and cavography are crucial in recognizing Badz-Chiari syndrome.
8. Esophagoscopy and gastroscopy allow us to identify varicose veins of the esophagus and stomach (in 69% of patients), which is a reliable sign of portal hypertension.
9. Esophagography - detection of varicose veins of the esophagus using fluoroscopy and radiography. In this case, varicose veins of the esophagus are determined as rounded enlightenments in the form of a chain or branching stripes. At the same time, it is possible to see the expansion of veins in the cardiac section of the stomach. The study should be carried out with a thick barium suspension with the patient lying on his back.
10. Rectomanoscopy reveals varicose veins with the development of collaterals along the mesenteric-hemorrhoidal tract. Varicose veins up to 6 mm in diameter are visible under the mucous membrane of the rectum and sigmoid colon.
11. Selective arteriography (celiacography, etc.) is rarely used, usually before surgery. The method allows us to draw conclusions about the state of blood flow in the hepatic artery.
12. Computer tomography

After the contrast agent is administered, it becomes possible to determine the lumen of the portal vein and identify varicose veins located in the retroperitoneal space, as well as perivisceral and paraesophageal veins. Varicose veins of the esophagus bulge into its lumen, and this bulge becomes more noticeable after the contrast agent is administered. The umbilical vein can be identified. Varicose veins of the stomach are visualized as ring-shaped structures indistinguishable from the stomach wall.

CT with arterial portography allows identification of collateral blood flow pathways and arteriovenous shunts.

13. Magnetic resonance imaging

Magnetic resonance imaging (MRI) allows for very clear visualization of vessels, as they are not involved in signal generation, and for studying them. It is used to determine the lumen of shunts, as well as to assess portal blood flow. Magnetic resonance angiography data are more reliable than Doppler ultrasound data.

14. Abdominal radiography helps to detect ascites, hepatomegaly and splenomegaly, calcification of the hepatic and splenic arteries, calcifications in the main trunk or branches of the portal vein.

X-ray examination allows us to determine the size of the liver and spleen. Occasionally, it is possible to identify a calcified portal vein; computed tomography (CT) is more sensitive.

In cases of intestinal infarction in adults or enterocolitis in infants, linear shadows caused by gas accumulations in the branches of the portal vein, especially in the peripheral areas of the liver, are occasionally seen; the gas is formed as a result of the activity of pathogenic microorganisms. The appearance of gas in the portal vein may be associated with disseminated intravascular coagulation. CT and ultrasound examination (US) reveal gas in the portal vein more often, for example, in purulent cholangitis, in which the prognosis is more favorable.

Tomography of the azygos vein can reveal its enlargement, since a significant portion of collaterals flow into it.

There may be an expansion of the shadow of the left paravertebral region, caused by the lateral displacement of the section of the pleura between the aorta and the spinal column by the expanded hemiazygos vein.

With significant expansion of the paraesophageal collateral veins, they are revealed on a plain chest X-ray as a volumetric formation in the mediastinum located behind the heart.

Barium study

Barium studies have become largely obsolete since the introduction of endoscopic techniques.

A small amount of barium is needed to examine the esophagus.

Normally, the mucous membrane of the esophagus looks like long, thin, evenly spaced lines. Varicose veins look like filling defects against the background of a smooth contour of the esophagus. They are most often located in the lower third, but can spread upward and be detected along the entire length of the esophagus. Their detection is facilitated by the fact that they are dilated and as the disease progresses, this dilation can become significant.

Esophageal varices are almost always accompanied by dilation of the gastric veins that pass through the cardia and line the fundus; they have a vermiform appearance, so they can be difficult to distinguish from mucosal folds. Sometimes gastric varices appear as a lobular formation at the fundus of the stomach, resembling a cancerous tumor. Contrast portography can help in the differential diagnosis.

15. Venography

If portal vein patency is established by any method in liver cirrhosis, confirmation by venography is not mandatory; it is indicated when planning liver transplantation or portal vein surgery. If portal vein thrombosis is suspected based on scintigraphy, venography is necessary to verify the diagnosis.

Portal vein patency is of great importance in the diagnosis of splenomegaly in children and for excluding invasion of the portal vein by hepatocellular carcinoma that develops against the background of cirrhosis.

The anatomical structure of the portal venous system should be studied before procedures such as portosystemic shunting, liver resection or transplantation. Venography may be required to confirm the patency of the imposed portosystemic shunt.

In the diagnosis of chronic hepatic encephalopathy, the severity of collateral circulation in the portal vein system is of great importance. The absence of collateral circulation excludes this diagnosis.

Phlebography can also reveal a filling defect in the portal vein or its branches, indicating compression by a volumetric formation.

Portal vein on venograms

If the blood flow in the portal vein is not impaired, then only the splenic and portal veins are contrasted. At the confluence of the splenic and superior mesenteric veins, a filling defect may be detected, caused by mixing of contrast and normal blood. The size and course of the splenic and portal veins are subject to significant fluctuations. Inside the liver, the portal vein gradually branches and the diameter of its branches decreases. After some time, the transparency of the liver tissue decreases due to filling of the sinusoids. On later radiographs, the hepatic veins are usually not visible.

In liver cirrhosis, the venographic picture is quite variable. It may remain normal or numerous collateral vessels and significant distortion of the intrahepatic vascular pattern may be visible (the "tree in winter" picture).

With extrahepatic portal vein obstruction or splenic vein obstruction, blood begins to flow back through the numerous vessels connecting the spleen and splenic vein with the diaphragm, chest, and abdominal wall.

Intrahepatic branches are usually not detected, although with a short block of the portal vein, blood can flow around the blocked area through bypass vessels that flow into the distal parts of the portal vein; in this case, the intrahepatic veins are clearly visualized, although with some delay.

16. Evaluation of hepatic blood flow

Continuous dye injection method

Hepatic blood flow can be measured by injecting indocyanine green at a constant rate and placing a catheter in the hepatic vein. Blood flow is calculated using the Fick method.

To determine blood flow, a dye is needed that is removed only by the liver and at a constant rate (evidenced by stable arterial pressure) and does not participate in the enterohepatic circulation. Using this method, a decrease in hepatic blood flow has been demonstrated in the lying position of the subject, in fainting, heart failure, cirrhosis and physical exertion. Hepatic blood flow increases in fever, but does not change with an increase in cardiac output, observed, for example, in thyrotoxicosis and pregnancy.

Method based on determination of extraction from plasma

Hepatic blood flow can be measured after intravenous administration of indocyanine green by analyzing dye concentration curves in the peripheral artery and hepatic vein.

If the substance is extracted by the liver almost 100%, as is observed, for example, when using a colloidal complex of heat-denatured albumin with ¹³¹ I, hepatic blood flow can be estimated from the clearance of the substance from the peripheral vessels; in this case, there is no need to catheterize the hepatic vein.

In cirrhosis, up to 20% of the blood passing through the liver may be diverted away from the normal blood flow pathway and the liver's elimination of substances is reduced. In these cases, hepatic vein catheterization is necessary to measure hepatic extraction and thus assess hepatic blood flow.

Electromagnetic flowmeters

Electromagnetic flowmeters with a rectangular pulse shape allow separate measurement of blood flow in the portal vein and hepatic artery.

Blood flow through the azygos vein

The major part of the blood flowing through the varicose veins of the esophagus and stomach enters the azygos vein. Blood flow through the azygos vein can be measured by thermodilution using a double catheter inserted into the azygos vein under fluoroscopic control. In alcoholic cirrhosis complicated by bleeding from varicose veins, the blood flow is about 596 ml/min. Blood flow through the azygos vein decreases significantly after the administration of propranolol.

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