Portal hypertension – causes, symptoms, diagnosis, treatment, pathology

Learning medicine is hard work, Osmosis makes it easy. Portal hypertension means increased blood pressure in the hepatic portal system or portal venous system. Most commonly, this happens because of hepatic cirrhosis, which is when the liver tissue is replaced by fibrotic functionless tissue. Now, the portal venous system comprises of the portal vein and its tributaries, namely the Splenic and Mesenteric veins. This blood contains all the nutrients absorbed in the GI tract, but it also carries toxins that the liver metabolizes so that they can be safely excreted by the kidneys. Once the liver processes all these substances, it sends the blood to the heart through the inferior vena cava to enter the systemic venous system. Now there are a few points in the boundaries of the hepatic portal system where it could be connected with the systemic venous system that collects blood from the rest of the body. The inferior portion of the esophagus, the superior portion of the anal canal, and the round ligament of the liver, which used to be the umbilical vein during fetal life. At birth, the umbilical cord is cut and the umbilical vein collapses to form the round ligament. The round ligament stay shut because pressures in the portal venous system and the systemic venous system are the same under 12 mmHg. But in some situations, an obstruction may prevent blood flow from the portal vein towards the inferior vena cava. When this happens, venous blood accumulates in the hepatic portal system, causing pressure to rise above 12 mmHg, which defines portal hypertension. Portal hypertension leads to the formation of Portosystemic shunts, which is when blood is diverted away from the portal venous system and backs up into the systemic veins. So first, less blood gets to the liver, causing diminished liver function and decreased blood detoxification, which leads to a buildup of toxic metabolites, like ammonia in the blood. Ammonia and other toxins can pass through the blood brain barrier and cause hepatic encephalopathy. Second, blood backing up in the systemic veins leads to portal systemic shunts, which happens in the three points where the systemic venous system and hepatic portal system are connected. In the esophagus, this causes esophageal varices or enlarged esophageal veins. In fact, portal hypertension is the most common cause of esophageal varices. These varices are very fragile and could easily rupture, causing massive upper GI bleeding. In the rectum and anal canal, there may be hemorrhoids, which are enlarged veins that can bleed as well. Finally, portal hypertension causes the round ligament to re-channel, allowing blood from the portal system to pass into the systemic veins of the abdomen, which then dilate, making the abdomen look like the head of the Greek mythological creature Medusa, the one with snakes for hair. So this consequence is frequently named Caput Medusae. Portal hypertension can also cause blood to back up into the spleen causing congestive splenomegaly, meaning the enlarged spleen. This causes hypersplenism, meaning the spleen traps blood elements like red blood cells, which causes anemia, and white blood cells, which can cause leukopenia, or platelets, causing Thrombocytopenia. Another consequence of portal hypertension is that the endothelial cells lining the blood vessels release more nitric oxide. The reason behind this is unclear, but nitric oxide makes peripheral arteries dilate, so blood pressure drops. This stimulates the release of aldosterone, which tries to bring blood pressure back up by telling the kidneys to retain more sodium and water. In time, plasma volume expands so much that fluid in blood vessels is more likely to get pushed into tissues and across tissues into large open spaces, like the peritoneal cavity, The accumulation of fluid in the peritoneal cavity is called ascites. As if that wasn’t enough, bacteria can also invade the peritoneal cavity causing spontaneous bacterial peritonitis. The features of portal hypertension can be remembered as ABCDE, where A stands for Ascites, B for Bleeding, C for Caput Medusae, D for Diminished liver function, and E for Enlarged spleen. Now causes of portal hypertension can be classified as pre-hepatic, intra-hepatic or post-hepatic, depending on where the obstruction is. The most common pre-hepatic cause is portal vein obstruction, like when there’s a thrombus occluding the portal vein and blocking blood flow. Intra-hepatic causes include cirrhosis, schistosomiasis, which is when flatworms invade the liver; and sarcoidosis, which is when inflammatory cells form lumps called Granulomas inside the liver. Cirrhosis is by far the most common of the three. Post-hepatic causes include right-sided Heart failure, Constrictive Pericarditis and Budd-Chiari syndrome. Both right-sided heart failure and constrictive Pericarditis restrict the blood flow from the heart to the lungs and to the rest of the body, causing blood to accumulate downwards, including into the portal circulation; and Budd-Chiari syndrome occurs when a thrombus or a tumor inside the hepatic veins that obstruct hepatic venous flow toward the inferior vena Cava. Portal hypertension may be asymptomatic until complications occur. Visible signs include a distended abdomen with ascites, and Caput Medusae or visibly engorged superficial abdominal veins. GI bleeding secondary to esophageal varices can present with hematemesis or vomiting blood, or melena or hematochezia when there’s blood in the stool With liver impairment, jaundice may occur. And finally, with hepatic encephalopathy, there may be Asterixis, which means hand tremor when the wrist is extended; altered consciousness, lethargy, seizure, or coma. The gold standard for determining if there is portal hypertension is obtaining a hepatic venous pressure gradient measurement where a catheter is inserted inside the inferior vena cava and then inside the portal vein to measure the difference between both pressures. A liver ultrasound might be useful to detect nodules in case of cirrhosis. CT scan or MRI help diagnose ascites, cirrhosis, splenomegally or vascular alterations like inferior vena cava dilatation. Labs including full blood count, liver enzymes and serology can be useful to identify the cause and an upper GI Endoscopy can identify esophageal varices in order to treat them appropriately. Treatment is centered on prevention and treatment of complications. Beta-blockers like propranolol can decrease portal venous pressure and prevent complications. For ascites, diuretic and sodium restriction are indicated to reduce the fluid overload. If esophageal varices bleed, a medication called octreotide, and procedures like balloon tamponade, sclerotherapy and variceal ligation can be used. To prevent bleeding from happening again, an interventional radiology technique called TIPS is the preferred procedure to decrease hepatic portal pressure and prevent further complications. With TIPS, a tube is inserted via a catheter to allow communication between the portal vein and hepatic vein. All right, as a quick recap, portal hypertension is when the pressure in the hepatic portal system is greater than 12 mmHg. This happens when there’s an obstruction in the passage of blood from the portal vein towards the vena cava. So venous blood accumulates downward from the obstruction, causing features like ascites, esophageal varices and bleeding, Caput Medusae, diminished liver function and an enlarged spleen. The most common cause of portal hypertension is cirrhosis. Diagnosis is done mainly by hepatic venous pressure gradient measurement. Prevention of complications can be done with beta-blockers and treatment options include diuretics for ascites, and octreotide, balloon tamponade, sclerotherapy, and a variceal ligation for bleeding esophageal varices. To prevent bleeding from happening again, as well as further complications, a Transjugular Intra-hepatic Portosystemic Shunt or TIPS can be done.

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