|
Portal hypertension
is caused most often by cirrhosis (in developed countries), schistosomiasis (in
endemic areas), or hepatic vascular abnormalities. Consequences
include esophageal varices and portal-systemic encephalopathy. Diagnosis
is based on clinical criteria, often in conjunction with imaging
studies and endoscopy. Treatment involves prevention of GI bleeding
with endoscopy, drugs, or both, and sometimes with portocaval shunting.
The portal vein, formed by the superior mesenteric and splenic veins, drains blood from the abdominal GI tract, spleen, and pancreas into the liver. Within reticuloendothelium-lined blood channels (sinusoids), blood from the terminal portal venules merges with hepatic arterial blood. Blood flows out of the sinusoids via the hepatic veins into the inferior vena cava.
Normal portal pressure is 5 to 10 mm Hg (7 to 14 cm H2O), which exceeds inferior vena caval pressure by 4 to 5 mm Hg (portal venous gradient). Higher values are defined as portal hypertension.
Etiology
and Pathophysiology
Portal hypertension results mainly from increased resistance to flow, which commonly arises from disease within the liver itself or uncommonly from blockage of the splenic or portal vein or impaired hepatic venous outflow (see Table 1: Approach to the Patient With Liver Disease: Classification and Most Common Causes of Portal Hypertension ). Increased flow volume is a rare cause, although it often contributes to portal hypertension in cirrhosis and in hematologic disorders that produce massive splenomegaly.
|
Table 1
|
 | | |
|
Classification
and Most Common Causes
of Portal Hypertension
|
|
Classification
|
Cause
|
|
Prehepatic
|
Portal or splenic vein thrombosis
Increased portal flow: arteriovenous fistula, massive splenomegaly from primary hematologic disease
|
|
Hepatic
|
Presinusoidal: schistosomiasis, other periportal disorders (eg, primary biliary cirrhosis, sarcoidosis, congenital hepatic fibrosis), idiopathic portal hypertension
Sinusoidal: cirrhosis (all etiologies)
Postsinusoidal: veno-occlusive disease
|
|
Posthepatic
|
Hepatic vein thrombosis (Budd-Chiari syndrome)
Obstruction of the inferior vena cava
Resistance to right heart filling (eg, constrictive pericarditis, restrictive cardiomyopathy)
|
|
In cirrhosis, tissue fibrosis and regeneration increase resistance in the sinusoids and terminal portal venules. However, other, potentially reversible, factors contribute, such as contractility of sinusoidal lining cells, production of vasoactive substances (eg, endothelins, nitric oxide), various systemic mediators of arteriolar resistance, and, possibly, swelling of hepatocytes.
Over time, portal hypertension creates portal-systemic venous collaterals. These may slightly decrease portal vein pressure but can produce complications. Engorged serpentine submucosal vessels (varices) in the distal esophagus and sometimes in the gastric fundus can rupture, causing sudden, catastrophic GI bleeding. Bleeding rarely occurs unless the portal pressure gradient is > 12 mm Hg. Gastric mucosal vascular congestion (portal hypertensive gastropathy) can cause acute or chronic bleeding independent of varices. Visible abdominal wall collaterals are common; veins radiating from the umbilicus (caput medusae) are much rarer and indicate extensive flow in the umbilical and periumbilical veins. Collaterals around the rectum can produce rectal varices that can bleed.
Portal-systemic collaterals shunt blood away from the liver. Thus, less blood reaches the liver when portal flow increases (diminished hepatic reserve). In addition, toxic substances from the intestine are shunted directly to the systemic circulation, contributing to portal-systemic encephalopathy (see Approach to the Patient With Liver Disease: Portal-Systemic Encephalopathy). Venous congestion within visceral organs due to portal hypertension contributes to ascites via altered Starling's forces. Splenomegaly and hypersplenism (see Spleen Disorders: Splenomegaly) commonly occur as a result of increased splenic vein pressure. Thrombocytopenia, leukopenia, and, less commonly, hemolytic anemia may result.
Portal hypertension is often associated with a hyperdynamic circulation. Mechanisms are complex and appear to involve altered sympathetic tone, production of nitric oxide and other endogenous vasodilators, and enhanced activity of humoral factors (eg, glucagon).
Symptoms,
Signs, and Diagnosis
Portal hypertension is asymptomatic; symptoms and signs result from its complications. The most dangerous is acute variceal bleeding (see GI Bleeding: Varices). Patients typically present with sudden painless upper GI bleeding, often massive. Bleeding from portal hypertensive gastropathy is often subacute or chronic. Ascites, splenomegaly, or portal-systemic encephalopathy may be present.
Portal hypertension is inferred in a patient with chronic liver disease by the presence of collateral circulation, splenomegaly, ascites, or portal-systemic encephalopathy. Proof requires direct portal pressure measurement by a transjugular catheter, which is invasive and usually not performed. Imaging may help when cirrhosis is suspected. Ultrasound or CT often reveals dilated intra-abdominal collaterals, and Doppler ultrasound can determine portal vein patency and flow.
Esophagogastric varices and portal hypertensive gastropathy are best diagnosed by endoscopy, which may also identify predictors of esophagogastric variceal bleeding (eg, red markings on a varix).
Prognosis
and Treatment
Mortality during acute variceal hemorrhage may exceed 50%. Prognosis is predicted by the degree of hepatic reserve and the degree of bleeding. For survivors, the bleeding risk within the next 1 to 2 yr is 50 to 75%. Ongoing endoscopic or drug therapy lowers the bleeding risk but decreases long-term mortality only marginally. Treatment of acute bleeding is discussed in GI Bleeding: Treatment.
When possible, the underlying disorder is treated. Long-term treatment of esophagogastric varices that have bled is a series of endoscopic banding or sclerotherapy sessions to obliterate residual varices, then surveillance endoscopy every few months for recurrent varices. Banding is generally preferable to sclerotherapy because of lower risks.
Long-term drug therapy for varices that have bled involves β‑blockers; these drugs lower portal pressure primarily by diminishing portal flow, although the effects vary. Propranolol (40 to 80 mg po bid) or nadolol (40 to 160 mg po once/day) is preferred, with dosage titrated to decrease heart rate by about 25%. Adding isosorbide mononitrate 10 to 20 mg po bid may further reduce portal pressure. Combined long-term endoscopic and drug therapy may be slightly more effective than either alone. Patients who do not adequately respond to either treatment should be considered for transjugular intrahepatic portal-systemic shunting (TIPS) or a surgical portocaval shunt. TIPS creates a stent between the portal and hepatic venous circulation within the liver See also the American Association for the Study of Liver Disease's practice guideline The
Role of Transjugular Intrahepatic Portosystemic Shunt in the Management
of Portal Hypertension. Although TIPS may result in fewer immediate deaths than surgical shunting, particularly during acute bleeding, it often needs to be repeated because the stent becomes stenosed or occluded with time. Long-term benefits are unknown. Liver transplantation may help some patients.
For patients with varices that have not yet bled, β‑blockers lower the risk of bleeding.
For bleeding from portal hypertensive gastropathy, drugs can be used to decrease portal pressure. A shunt should be considered if drugs fail, but results may be less successful than for esophageal variceal bleeding.
Because it rarely causes clinical problems, hypersplenism requires no specific treatment, and splenectomy should be avoided.
Last full review/revision November 2005
Content last modified November 2005
| 
