Portal hypertension can cause variceal bleeding leading to hematemesis. Portal hypertension is abnormally elevated portal venous blood pressure above 5 mmHg (Turco & Garcia-Tsao, 2019). The pathology is a complication of end-stage liver diseases such as cirrhosis due to alcoholic liver disease and viral hepatitis. The disorders obstructing blood flow in the portal system can be classified into intrahepatic or posthepatic causes (Iwakiri & Trebicka, 2021). The intrahepatic causes increased vascular resistance resulting from vascular remodeling. Posthepatic causes result from thrombosis or disorders that impair the pumping ability of the right side of the heart.
Liver cirrhosis is the most common cause of intrahepatic vascular resistance via various mechanisms. Cells such as hepatic stellate cells (HSCs) and liver sinusoidal endothelial cells (LSECs) undergo various phenotypic changes in the cirrhotic liver (Iwakiri & Trebicka, 2021). LSECs act as the first line against hepatocyte injury, causing vasoconstriction, inflammation, fibrosis, and impaired regeneration. Production of vasodilators such as nitric oxide is diminished in cirrhosis. The decreased NO production is caused by the increased production of caveolin-1, which inhibits NO synthesizing enzymes and increases oxidative stress on the cell (Iwakiri & Trebicka, 2021). In addition to the decreased vasodilators, the production of vasoconstrictors is increased. The most markedly increased vasoconstrictor is thromboxane A2 produced by the action of COX-1 in the LSECs.
After the injury, HSCs are activated and transformed into myofibroblasts which express several pro-inflammatory and fibrotic genes (Iwakiri & Trebicka, 2021). The activated HSCs are contractile hence increasing intrahepatic vascular resistance. The myofibroblasts have a decreased response to vasodilators such as nitric oxide and increased responsiveness to ET-1, which is upregulated in cirrhosis. Angiogenesis increases the number of vessels in the septa surrounding the regenerative nodules in cirrhotic livers. The activated HSCs release angiopoietin and VEGF, which activate LSCEs and angiogenesis. Thrombosis and narrowing of the hepatic portal vein may cause prehepatic portal hypertension. Long-standing portal hypertension causes several pathologic complications, such as varices, ascites, splenomegaly, hepatic encephalopathy, and hepatopulmonary syndrome (Simonetto et al., 2019).
Varices are collateral veins that are distended and tortuous, caused by continuously elevated portal hypertension (Simonetto et al., 2019). The collateral veins join the portal venous circulation with the systemic venous circulation and are distended to shunt blood. Varices develop in the lower esophagus causing esophageal varices, or in the rectum causing hemorrhoidal varices. Rapture of the esophageal varices causes massive life-threatening hemorrhage characterized by hematemesis. Varices may also develop in the anterior abdominal wall around the umbilicus, causing the characteristic symptom caput medusa.
Splenomegaly is the enlargement of the spleen and is seen in portal hypertension (Simonetto et al., 2019). The splenic vein branches from the portal vein; hence the pressure increases in portal hypertension, causing congestive splenomegaly. The enlarged spleen sequesters platelets causing thrombocytopenia and increased bleeding tendencies. An enlarged spleen can be palpated on the upper left quadrant of the abdomen during a general patient examination. Hepatopulmonary syndrome causes vasodilation and increased congestion in the pulmonary capillaries. The hypoxemia associated with hepatopulmonary syndrome causes dyspnea, digital clubbing, and cyanosis.
The clinical manifestations of portal hypertension are vomiting blood, the distention of the abdominal wall due to ascites, rectal bleeding, and caput medusa (Iwakiri & Trebicka, 2021). Chronic bleeding from the varices may cause anemia and dark stool (melena). Most clinical diagnoses of portal hypertension are made after the presentation of variceal bleeding. Varices are confirmed by endoscopy, and the portal venous pressure is measured to confirm the presence of portal hypertension. Magnetic resonance imaging can measure the stiffness and extent of liver fibrosis (Iwakiri & Trebicka, 2021). Nonselective beta-blockers and endoscopic vein ligation are used to stop variceal bleeding. Fluid replacement, red cell replacement, and terlipressin are administered to manage emergency bleeding. Surgery can be done to construct a transjugular intrahepatic portosystemic shunt. There is no definitive treatment for portal hypertension, but a liver transplant may help improve the condition.
References
Iwakiri, Y., & Trebicka, J. (2021). Portal hypertension in cirrhosis: Pathophysiological mechanisms and therapy. JHEP Reports: Innovation in Hepatology, 3(4), 100316. https://doi.org/10.1016/j.jhepr.2021.100316
Simonetto, D. A., Liu, M., & Kamath, P. S. (2019). Portal Hypertension and Related Complications: Diagnosis and Management. Mayo Clinic Proceedings, 94(4), 714–726. https://doi.org/10.1016/j.mayocp.2018.12.020
Turco, L., & Garcia-Tsao, G. (2019). Portal Hypertension: Pathogenesis and Diagnosis. Clinics in Liver Disease, 23(4), 573–587. https://doi.org/10.1016/j.cld.2019.07.007
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