The portal vein and its tributaries.
|Classification and external resources|
Portal hypertension is defined as elevation of hepatic venous pressure gradient to >5mmHg. Generally, in clinical practice the pressure is not measured directly until the decision to place a transjugular intrahepatic portosystemic shunt (TIPS) has already been made. As part of that procedure, a hepatic vein wedge pressure is measured with the assumption of no pressure drop across the liver yielding portal vein pressure.
Causes can be divided into pre-hepatic, intra-hepatic, and post-hepatic.
- Prehepatic causes include portal vein thrombosis or congenital atresia.
- Intrahepatic causes include liver cirrhosis, hepatic fibrosis (e.g. due to Wilson's disease, hemochromatosis, or congenital fibrosis), and less commonly noncirrhotic causes such as schistosomiasis, massive fatty change and diffuse granulomatous diseases (e.g. sarcoidosis, miliary tuberculosis).
- Posthepatic obstruction occurs at any level between liver and right heart, including hepatic vein thrombosis, inferior vena cava thrombosis, inferior vena cava congenital malformation, and constrictive pericarditis.
Signs and symptoms
Consequences of portal hypertension are caused by blood being forced down alternate channels by the increased resistance to flow through the systemic venous system rather than the portal system. They include:
- Ascites (free fluid in the peritoneal cavity).
- Hepatic encephalopathy.
- Increased risk of spontaneous bacterial peritonitis.
- Increased risk of hepatorenal syndrome.
- Splenomegaly (enlargement of the spleen) with a consequent accumulation of red blood cells, white blood cells, and platelets, together leading to mild pancytopenia.
- Development of varices at portacaval anastomoses: Esophageal varices, gastric varices, anorectal varices (not to be confused with hemorrhoids), and caput medusae. Esophageal and gastric varices pose an ongoing risk of life-threatening bleeding, with bloody vomiting or melena.
HVPG (hepatic venous pressure gradient) measurement has been accepted as the gold standard for assessing the severity of portal hypertension, and replaced the old one - contrast angiography. Portal hypertension is defined as HVPG greater than or equal to 5mm Hg and is considered to be clinically significant when HVPG exceeds 10 to 12 mm Hg.
These can be categorized by several different concepts: selective vs non-selective, mesocaval vs portocaval, and the specific arrangement of vessels, e.g. end-to-side or side-to-side. Selective shunts select non-intestinal flow to be shunted to the systemic venous drainage while leaving the intestinal venous drainage to continue pass through the liver. The most well known of this type is the splenorenal, or Warren, shunt. 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, unlikely, portocaval (from the portal vein to the inferior vena cava) a graft, either synthetic or the preferred vein harvested from somewhere else 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.
It should be noted that with the advent of transjugular intrahepatic portosystemic shunting (TIPS), portosystemic shunts are now very rarely performed. TIPS has the advantage of being much easier to perform and it doesn't disrupt any of the liver's vascularity, which will be needed if a given patient's hopes for liver transplant. In general, non-selective shunts are emergency surgeries that are done as quickly as possible to minimize intraoperative blood loss. On the contrary, a splenorenal shunt would be an elective procedure due to its great technical demands. Further contributing to their rare use today is the fact that few, if any, current general surgery residents are trained in how to carry out these surgeries.
Prophylaxis of variceal bleeding
Both pharmacological (non-specific ß-blockers like Propranolol and isosorbide mononitrate) and endoscopic (banding ligation) treatment have similar results. TIPS (transjugular intrahepatic portosystemic shunting) is superior to either of them at reducing rate of rebleeding. Disadvantages of TIPS include high cost and increased risk of hepatic encephalopathy, and it does not improve the mortality rate.
Management of active variceal bleeding
After resuscitation, which may require blood transfusion, the management of active variceal bleeding includes administering vasoactive drugs (somatostatin, octreotide or terlipressin), endoscopic banding ligation, balloon tamponade and TIPS(Transjugular intrahepatic portocaval shunt)
Management of ascites
This should be gradual to avoid sudden changes in systemic volume status which can precipitate hepatic encephalopathy, renal failure and death. The management includes salt restriction, diuretics (spironolactone), paracentesis, transjugular intrahepatic portosystemic shunt (TIPS) and peritoneovenous shunt.
Control of hepatic encephalopathy
A standard treatment plan may involve lactulose, bowel enemas, and use of oral antibiotics such as rifaximin, neomycin, metronidazole, vancomycin, and the quinolones. Previously, restriction of dietary protein was recommended but this is now refuted by a clinical trial which showed no benefit. Instead, the maintenance of adequate nutrition is now advocated.
- Perkins, [edited by] Vinay Kumar, Abul K. Abbas, Jon C. Aster ; artist, James A. Robbins basic pathology (9th ed. ed.). Philadelphia, PA: Elsevier/Saunders. p. 608. ISBN 978-1-4377-1781-5.
- "Portal Hypertension". Retrieved 2007-12-07.
- Appleton & Lange's review for the ultrasonography examination, By Carol Krebs, Charles S. Odwin, Arthur C. Fleischer, page 309
- Córdoba, J.; López-Hellín, J.; Planas, M.; Sabín, P.; Sanpedro, F.; Castro, F.; Esteban, R.; Guardia, J. (2004). "Normal protein diet for episodic hepatic encephalopathy: Results of a randomized study". Journal of Hepatology 41 (1): 38–43. doi:10.1016/j.jhep.2004.03.023. PMID 15246205.
- VIDEO - Portal Hypertension: Shunt Surgery in the Era of Transplant and TIPS, Alysandra Lal, MD, speaks at the University of Wisconsin School of Medicine and Public Health (2007)
- Ascites at Merck Manual of Diagnosis and Therapy Home Edition
- 00863 at CHORUS
- Overview at Cleveland Clinic
- Children's Liver Disease Foundation