Portal Hypertension Flashcards
Variceal hemorrhage, hepatic encephalopathy, and ascites—the major complications of cirrhosis of the liver
result from portal hypertension, defined as an increase in hepatic sinusoidal pressure to 6 mm Hg or greater
The portal vein is formed by the confluence
of the splenic vein and the superior mesenteric vein behind the neck of the pancreas
The portal vein
is approximately 7.5 cm in length and runs dorsal to the hepatic artery and bile duct into the hilum of the liver.
In the hilum of the liver,
the portal vein divides into the left and right portal vein branches, which supply the left and right sides of the liver
The umbilical vein
drains into the left portal vein, and the cystic vein from the gallbladder drains into the right portal vein.
The liver receives a dual blood supply from the
portal vein and the hepatic artery that constitutes nearly 30% of total cardiac output.
Portal venous blood derived from the
mesenteric venous circulation constitutes approximately 75% of total hepatic blood flow, whereas the remainder of blood to the liver is derived from the hepatic artery, which provides highly oxygenated blood directly from the celiac trunk of the aorta.
Other unique aspects of the hepatic sinusoids are
the space of Disse, a virtual space located extraluminal to the endothelial cell and adjacent to the hepatocyte, and its cellular constituents, the hepatic stellate cell (HSC) and the Kupffer cell
Four distinct zones of venous drainage at the gastroesophageal junction are particularly relevant to the formation of esophageal varices
The gastric zone, which extends for 2 to 3 cm below the gastroesophageal junction, comprises veins that are longitudinal and located in the submucosa and lamina propria. They come together at the upper end of the cardia of the stomach and drain into short gastric and left gastric veins.
Four distinct zones of venous drainage at the gastroesophageal junction are particularly relevant to the formation of esophageal varices
The palisade zone extends 2 to 3 cm proximal to the gastric zone into the lower esophagus.
The palisade zone is the dominant watershed area between the portal and systemic circulations.
Four distinct zones of venous drainage at the gastroesophageal junction are particularly relevant to the formation of esophageal varices
More proximal to the palisade zone in the esophagus is the perforating zone, where there is a network of veins. These veins are less likely to be longitudinal and are termed perforating veins because they connect the veins in the esophageal submucosa and the external veins.
Four distinct zones of venous drainage at the gastroesophageal junction are particularly relevant to the formation of esophageal varices
The truncal zone, the longest zone, is approximately 10 cm in length, located proximal to the perforating zone in the esophagus, and usually characterized by 4 longitudinal veins in the lamina propria.
The fundus of the stomach drains
through short gastric veins into the splenic vein.
progression of portal hypertension results from
1) the prominent obstructive resistance in the liver; (2) resistance within the collaterals themselves; and (3) continued increase in portal vein inflow.
Hepatic Vein Pressure Gradient
The HVPG is the difference between the wedged hepatic venous pressure (WHVP) and free hepatic vein pressure (FHVP).
Measurement of the HVPG has been proposed for the following indications:
1) to monitor portal pressure in patients
taking drugs used to prevent variceal bleeding; (2) as a prognostic marker (3) as an end point in trials using pharmacologic
agents for the treatment of portal hypertension; (4) to assess
the risk of hepatic resection in patients with cirrhosis; and (5) to
delineate the cause of portal hypertension (i.e., presinusoidal,
sinusoidal, or postsinusoidal usually in combination with venography, right-sided heart pressure measurements, and transjugular liver biopsy.
DETECTION OF VARICES
EGD is the most commonly used method to detect esophageal varices
If small varices are detected on the initial examination,
endoscopy should be repeated in 1 to 2 years.
In patients in whom no varices are detected on initial evaluation,
endoscopy to screen for varices should be repeated in 2 to 3 years.