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Portal hypertension

Portal hypertension is defined as increased portal venous pressure, with a hepatic venous pressure gradient greater than 5 mmHg. Normal portal pressure is 1–4 mmHg; clinically insignificant portal hypertension is present at portal pressures 5–9 mmHg; clinically significant portal hypertension is present at portal pressures greater than 10 mmHg. The portal vein and its branches supply most of the blood and nutrients from the intestine to the liver.

Signs and symptoms
Signs and symptoms of portal hypertension include: • Abdominal swelling and tightness due to ascites, which is free fluid in the peritoneal cavity • Vomiting blood (hematemesis) from gastric or esophageal varices • Anorectal varices • Increased spleen size (splenomegaly), ==Causes==
Causes
The causes for portal hypertension are classified as originating in the portal venous system before it reaches the liver (prehepatic causes), within the liver (intrahepatic) or between the liver and the heart (post-hepatic). The most common cause is cirrhosis (chronic liver failure). Other causes include: Prehepatic causesPortal vein thrombosisSplenic vein thrombosisArteriovenous fistula (increased portal blood flow) • Splenomegaly and/or hypersplenism (increased portal blood flow) Hepatic causesCirrhosis of any cause. • alcohol use disorderchronic viral hepatitisbiliary atresiaPrimary biliary cirrhosisPrimary sclerosing cholangitisChronic pancreatitisHereditary haemorrhagic telangiectasiaSchistosomiasisCongenital hepatic fibrosisNodular regenerative hyperplasia • Fibrosis of space of Disse • Granulomatous or infiltrative liver diseases (Gaucher disease, mucopolysaccharidosis, sarcoidosis, lymphoproliferative malignancies, amyloidosis, etc.) • Toxicity (from arsenic, copper, vinyl chloride monomers, mineral oil, vitamin A, azathioprine, dacarbazine, methotrexate, amiodarone, etc.) • Viral hepatitis • Fatty liver disease • Veno-occlusive disease Posthepatic causes • Inferior vena cava obstruction • Right-sided heart failure, e.g. from constrictive pericarditisBudd–Chiari syndrome also known as hepatic vein thrombosis ==Pathophysiology==
Pathophysiology
Cirrhotic portal hypertension The pathophysiology of cirrhotic portal hypertension is indicated by increased resistance to blood flow in vessels via different mechanisms. There is sinusoidal endothelial cell dysfunction (SEC), hepatic stellate cell (HSC) activation, Kupffer cell activation, and myofibroblast activation. Normally, SECs generate nitric oxide, which has several functions, including the maintenance of vascular tone and prevention of HSC activation. HSC activation results in liver fibrosis, which also predisposes to portal hypertension. Rising portal pressures leads to increased production of vasodilators, defective response to vasoconstrictors, and the formation of new blood vessels all within the splanchnic circulation. All of this is done in order to recruit more blood to sinusoids, thereby promoting more blood flow within the portal vein, further contributing to portal hypertension. Splanchnic vasodilation results in decreased effective arterial blood volume, causing low blood pressure. To compensate for this low blood pressure, neurohumoral factors (RAAS, SNS, ADH) are activated, leading to sodium and water retention, and therefore, a high volume state. Non-cirrhotic portal hypertension The pathophysiology of non-cirrhotic portal hypertension is most commonly disrupted blood flow to or from the liver. This results in a backing up of blood in either the liver or the vessels supplying it, leading to an increased portal pressure. ==Diagnosis==
Diagnosis
Ultrasonography (US) is the first-line imaging technique for the diagnosis and follow-up of portal hypertension because it is non-invasive, low-cost and can be performed on-site. A dilated portal vein (diameter of greater than 13 or 15 mm) is a sign of portal hypertension, with a sensitivity estimated at 12.5% or 40%. On Doppler ultrasonography, a slow velocity of <16 cm/s in addition to dilatation in the main portal vein are diagnostic of portal hypertension. Other signs of portal hypertension on ultrasound include a portal flow mean velocity of less than 12 cm/s, porto–systemic collateral veins (patent paraumbilical vein, spleno–renal collaterals and dilated left and short gastric veins), splenomegaly and signs of cirrhosis (including nodularity of the liver surface). ==Complications==
Complications
Ascites Pathogenesis The activation of neurohumoral factors as described in the "Pathophysiology" section results in a high volume state due to sodium and water retention. Additionally, with cirrhosis, there is increased hydrostatic pressure and decreased production of albumin, which lead to decreased oncotic pressure. Combined, this leads to leakage of fluid into the peritoneal cavity. Management The management of ascites needs to be gradual to avoid sudden changes in systemic volume status, which can precipitate hepatic encephalopathy, kidney failure, and death. The management includes salt restriction in diet, diuretics to urinate excess salt and water (furosemide, spironolactone), paracentesis to manually remove the ascitic fluid, and transjugular intrahepatic portosystemic shunt (TIPS). Spontaneous bacterial peritonitis Pathogenesis In cirrhosis, there is bacterial overgrowth in the intestinal tract and increased permeability of the intestinal wall. These bacteria (most commonly E. coli & Klebsiella) are able to pass through the intestinal wall and into ascitic fluid, leading to an inflammatory response. Management Antibiotic treatment is usually with a third generation cephalosporin (ceftriaxone or cefotaxime) after a diagnostic paracentesis. Patients are also given albumin. Management Both pharmacological (non-specific β-blockers, nitrate isosorbide mononitrate, vasopressin such as terlipressin) and endoscopic (banding ligation) treatment have similar results. TIPS (transjugular intrahepatic portosystemic shunting) is effective at reducing the rate of rebleeding. The management of active variceal bleeding includes administering vasoactive drugs (somatostatin, octreotide), endoscopic banding ligation, balloon tamponade and TIPS. Management A treatment plan may involve lactulose, enemas, and use of antibiotics such as rifaximin, neomycin, vancomycin, and the quinolones. Restriction of dietary protein was recommended but this is now refuted by a clinical trial which shows no benefit. Instead, the maintenance of adequate nutrition is now advocated. Hepatorenal syndrome Pathogenesis Activation of neurohumoral factors (discussed in the Pathophysiology section) leads to renal vasoconstriction, which results in decreased blood supply to the kidneys and therefore, a decreased glomerular filtration rate. This can be an acute kidney injury (HRS type 1) or a slowly progressive kidney failure (HRS type 2). This use of splanchnic vasoconstrictors increases mean arterial pressure, which increases the amount of blood supplied to the kidneys. ==Treatment==
Treatment
Portosystemic shunts Selective shunts select non-intestinal flow to be shunted to the systemic venous drainage while leaving the intestinal venous drainage to continue to pass through the liver. The most well known of this type is the splenorenal. This connects the splenic vein to the left renal vein thus reducing portal system pressure while minimizing any encephalopathy. In an H-shunt, which could be mesocaval (from the superior mesenteric vein to the inferior vena cava) or could be, portocaval (from the portal vein to the inferior vena cava) a graft, either synthetic or the preferred vein harvested from elsewhere on the patient's body, is connected between the superior mesenteric vein and the inferior vena cava. The size of this shunt will determine how selective it is. With the advent of transjugular intrahepatic portosystemic shunting (TIPS), portosystemic shunts are less performed. TIPS has the advantage of being easier to perform and doesn't disrupt the liver's vascularity. == References ==
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