You are in: eMedicine Specialties > Radiology > GASTROINTESTINAL Portal HypertensionArticle Last Updated: Apr 18, 2007AUTHOR AND EDITOR INFORMATIONSection 1 of 11
  Author: Ali Nawaz Khan, MBBS, LRCP, FRCS, FRCP, FRCR, Chairman of Medical Imaging, Professor of Radiology, NGHA, King Fahad Hospital, King Abdulaziz Medical City, Riyadh, Saudi Arabia Ali Nawaz Khan is a member of the following medical societies: American Institute of Ultrasound in Medicine, Radiological Society of North America, Royal College of Physicians, Royal College of Physicians and Surgeons of the USA, Royal College of Radiologists, and Royal College of Surgeons of England Coauthor(s): Sumaira Macdonald, MBChB, MRCP, FRCR, PhD, Lecturer, Sheffield University Medical School; Endovascular Fellow, Sheffield Vascular Institute; Murad Ali, MBBS, PhD, DTCD, Consulting Radiologist, Department of Radiology, Postgraduate Medical Institute, Lady Reading Hospital, Pakistan; David Sherlock, MBBS, FRCS, Consulting Staff, Department of Surgery, North Manchester General Hospital, Christie Hospital Editors: Eric P Weinberg, MD, Associate Professor, Department of Radiology, University of Rochester Medical Center, Strong Memorial Hospital; Bernard D Coombs, MB, ChB, PhD, Consulting Staff, Department of Specialist Rehabilitation Services, Hutt Valley District Health Board, New Zealand; George G Hartnell, MD, Professor of Radiology, Tufts University School of Medicine, Director of Cardiovascular and Interventional Radiology, Department of Radiology, Baystate Medical Center; Robert M Krasny, MD, Consulting Staff, Department of Radiology, The Angeles Clinic and Research Institute; Kyung J Cho, MD, FACR, William Martel Professor of Radiology, Fellowship Program Director, Department of Radiology, Division of Interventional Radiology, University of Michigan Medical School Author and Editor Disclosure Synonyms and related keywords: PH, portal HTN, portal venous pressure, hepatic venous pressure, portal venous flow, hematemesis, bleeding esophageal varices, portosystemic collateral vessels, portosystemic collaterals, cirrhosis, splenoportography INTRODUCTIONSection 2 of 11
  BackgroundPortal hypertension (PH) represents an increase of the hydrostatic pressure within the portal vein or its tributaries and is defined as an increase in the pressure gradient between the portal vein and hepatic veins or inferior vena cava (IVC). Most patients with venous PH have intrinsic liver disease. In PH, blood that normally flows through the liver is diverted into systemic veins because of increased resistance to portal venous flow. This diversion of portal venous blood occurs via exiting portosystemic communications (eg, coronary vein) and the opening of embryonic channels (eg, paraumbilical veins). The most common portosystemic anastomosis is via the coronary-gastroesophageal route, which occurs in 80-90% of patients and gives rise to lower esophageal and gastric varices. Hematemesis resulting from bleeding esophageal varices is the most common presentation in patients with PH, although other patients may seek medical help because of decompensated liver disease. Findings from duplex ultrasonography (US) and color Doppler imaging (CDI), MRI, CT, and endoscopy may support the diagnosis of PH. PathophysiologyPH is defined as an increase in pressure gradient between the portal vein and the hepatic veins or IVC.1 A pressure gradient of 12 mm Hg is regarded as clinically significant for PH. With such an increase in the pressure gradient, portosystemic collaterals develop. These bypass portal venous flow to the liver, diverting blood to the systemic veins. PH may develop in a variety of clinical circumstances, but by far, most instances are related to cirrhosis. The causes of PH can be divided into (1) posthepatic, (2) prehepatic, and (3) intrahepatic causes. The major causes of posthepatic causes of PH are right-sided heart failure, constrictive pericarditis, and Budd-Chiari syndrome (BCS). The prehepatic causes of PH include portal vein thrombosis (PVT) and portal compression or occlusion by biliary and pancreatic neoplasms and metastases. PH may be caused by increased flow secondary to arterioportal fistula, pancreatic arteriovenous malformations, and massive splenomegaly. The most common intrahepatic cause is cirrhosis. The common feature to all the causes is an increased resistance to portal venous flow, although in a few cases, increased inflow into the portal venous system is present. The basis of PH in cirrhosis is an increased resistance to portal venous flow at the level of the sinusoids due to the perisinusoidal deposition of collagen. This deposition results in narrowing and compression of the central veins caused by fibrosis. Pressure from regenerative nodules contributes to this compression. Arteriovenous anastomoses in a fibrous scar also contribute to the increased portal venous pressure. Cirrhosis has many causes. In alcoholic liver disease, serious PH may develop without cirrhosis. In a minority of patients with acute alcoholic hepatitis, progressive obliteration of central veins occurs with resultant centrilobular fibrosis. These changes result in severe outflow obstruction to portal venous flow, which leads to formation of ascites and esophageal varices. Although alcoholism and malnutrition result in nodular or Laennec-type cirrhosis, bile duct obstruction in biliary cirrhosis, schistosomiasis, prolonged congestive heart failure, and hepatitis cause postnecrotic cirrhosis. Whatever the cause of cirrhosis from a hemodynamic viewpoint, the common denominator is a progressive increase in resistance to portal venous blood flow that results in PH. Chronic portal vein obstruction is an important cause of PH, and has a variety of causes. Cavernous transformation of the portal vein, ie, development of periportal collaterals, occurs with long-standing PVT due to the development of multiple small vessels in and around the recanalizing or occluded main portal vein. A leash of fine or markedly enlarged serpiginous vessels is seen in place of the portal vein. The application of color and/or pulsed Doppler imaging shows blood flow in these periportal collaterals that form around the thrombosed portal vein or that replace the vein. Causes of PVT include the following:
Splenic vein thrombosis may be caused by abdominal trauma, tumors, or pancreatitis. Pressure is increased in areas drained by the splenic vein, while pressure in the portal vein remains normal (left-sided PH). The diagnosis is suspected in patients with gastric and/or esophageal varices and normal liver biopsy results. Splenectomy is curative. BCS is a manifestation of hepatic venous outflow obstruction. The hepatic outflow obstruction usually occurs at the level of the IVC; the hepatic vein; and, depending on the classification and the nomenclature, possibly at the venules. The causes of BCS are numerous. Two types exist: acute and chronic. An acute thrombosis of the main hepatic veins or the IVC causes the acute form. The chronic form is related to fibrosis of the intrahepatic veins, which is presumably related to inflammation. The classical presentation is with ascites, hepatomegaly, and abdominal pain. Hepatic venous occlusion results in the elevation of sinusoidal pressure, which leads to a delay or reversal of portal venous blood inflow, ascites, and morphologic changes in the liver. The last changes are reflected in abnormal liver function results. Both the acute and chronic forms result in severe centrilobular congestion, hepatocellular necrosis, and atrophy. Two other entities with similar clinical characteristics are severe right-sided heart failure and veno-occlusive disease of the liver. Hepatic veno-occlusive disease is characterized by inflammation of the post-sinusoidal venules, which results in fibrosis and venous occlusion. BCS has been variously classified. Some authors distinguish between primary BCS, which is associated with IVC webs, and secondary BCS, which is ascribed to a myriad of causes including tumor, thrombosis, and trauma. Other authors divide the disease according to the location of obstruction as follows: Type I disease is defined as occlusion of the IVC with or without secondary hepatic vein occlusion. Type II involves occlusion of the major hepatic veins. Type III disease entails obstruction of the small centrilobular venules (considered as veno-occlusive disease by some authors). The causes of BCS are numerous. Examples include the following:
In most cases of BCS, the hepatic venous outflow is not completely eliminated because a variety of accessory hepatic veins drain into the IVC above or below the site of obstruction. The most common of these accessory veins are the accessory inferior hepatic and caudate veins, which drain into the IVC inferior to the major hepatic veins. Vascular communications also exist via the azygos, intercostal, and paravertebral veins, which provide alternative pathways for hepatic venous drainage in BCS. Intrahepatic communication between the hepatic veins and portal veins also reverse flow in some portal venous branches, though flow in the main portal vein tends to remain centripetal. As in BCS, some hepatic venous drainage is preserved, and the caudate lobe hypertrophies, sometimes massively; this may produce secondary IVC obstruction. Other parts of the liver with preserved venous drainage may also undergo hypertrophy. Some venous drainage also occurs via the capsular veins, but this drainage is not sufficient to prevent peripheral atrophy in BCS. Parts of the liver with complete obstruction of its venous drainage tend to drain via the portal vein branches, depriving the involved parts of the liver of portal venous blood supply and the trophic affects of hormones. Hepatic hypertrophy and regeneration is always dependent on the trophic affect of portal blood supply. Thus, BCS is typically associated with peripheral atrophy of the liver and caudate and central hypertrophy. On cross-sectional imaging, the porta hepatis may be displaced anteriorly in BCS. Concomitant PVT may be present in 9-20% of patients with BCS. In idiopathic PH (Banti syndrome), no cirrhosis occurs, and the portal vein is patent. Liver biopsy results may be normal or may show fibrosis in the periportal areas and in the space of Disse, and dilatation of sinusoids and intimal thickening with eccentric sclerosis of peripheral portal vein walls may be noted. The disease is progressive with increasing PH, and the liver eventually becomes small and fibrotic. A number of exogenous toxins such as copper salts, vinyl chloride, and arsenic can create a similar clinical picture. Congenital hepatic fibrosis usually appears in childhood in association with autosomal recessive polycystic kidney disease, medullary sponge kidney, or Caroli disease. PH is a major consequence of this form of liver disease, and hepatic function is well maintained. Histologically, fibrous tissue is present within the hepatic parenchyma, with excess numbers of distorted terminal interlobular bile ducts and cysts that do not communicate with the bile ducts. In rare cases, hepatic sarcoidosis leads to hepatic fibrosis and PH. When deprived of portal venous blood, the liver depends more on hepatic arterial blood. The liver undergoes atrophic changes, shrinks, and has an impaired capacity to regenerate. The changes are related to the lack of hepatotrophic hormones, largely insulin and glucagon, which are responsible for maintaining the normal structure and function of the liver. Vessels in the collateral venous circulation, particularly esophageal varices, are usually not prominent at autopsy because the veins collapse after death. The spleen is enlarged and firm, with a thickened capsule. Malpighian bodies are inconspicuous. Histologically, sinusoids are dilated and lined by thickened epithelium. Histiocytes proliferate in the sinusoids with occasional erythrophagocytosis. Periarterial hemorrhages may progress to siderofibrotic nodules. The splenic artery and portal vein are enlarged and tortuous, and they may be aneurysmal. The portal and splenic veins may show endothelial hemorrhages, mural thrombi, and intimal plaques, which may become calcified. These veins may be unsuitable for successful portosystemic shunt procedures. Small, intrasplenic arterial aneurysms are seen in 50% of patients with cirrhosis. Hepatic changes depend on the cause of the PH. The degree of portal venous pressure is poorly correlated with the apparent degree of cirrhosis and fibrosis; a much better correlation is made with the degree of nodule formation. FrequencyUnited StatesPH is related to the frequency of cirrhosis. Alcohol intake is the most common cause of liver disease in Western nations. Alcoholic cirrhosis is discovered in 1.6-9.9% of autopsies in the United States. InternationalThe exact worldwide incidence of cirrhosis is not known, but large regional variations occur depending on the frequency of hepatitis B and hepatitis C. Mortality/MorbidityMortality and morbidity are related to the underlying cause of PH, eg, cirrhosis, PVT and/or splenic vein thrombosis, and veno-occlusive disease. Hemorrhage due to esophageal varices is a major complication of PH. Mortality rates in adults with cirrhosis vary and are 30-60% for each bleeding episode. RaceThe most common cause of cirrhosis in North America is alcohol intake. In Africa, the Middle East, and the Far East, cirrhosis is virus related. Noncirrhotic idiopathic PH is more common in India and Japan. SexAlcohol-related cirrhosis frequently affects males, although the incidence in females is increasing. The male-to-female ratio is 2:1. Primary biliary cirrhosis has a female preponderance (>90%). AgeThe incidence of alcoholic cirrhosis peaks in patients aged 40-55 years; however, patients aged 20-30 years can also have advanced alcoholic liver disease. Primary biliary cirrhosis is found in patients as young as 23 years and as old as 72 years; however, most patients are aged 40-60 years. AnatomyThe portal venous system includes all veins that carry blood from the abdominal part of the alimentary tract, spleen, pancreas, and gallbladder. The union of the superior mesenteric and splenic veins forms the portal vein posterior to the pancreatic head. The portal vein enters the liver at the porta hepatis and soon divides into left and right portal vein branches. When portal circulation is obstructed, a remarkable collateral circulation develops, redirecting portal venous blood into systemic veins. Portosystemic collaterals are classified into 4 main groups as follows:
Spontaneous splenorenal shunts are seen in 10-20% of patients with PH. Blood from gastroesophageal collaterals and retroperitoneal and venous systems of the abdomen ultimately reaches the superior vena cava via the azygos or hemiazygos system. A small volume of blood enters the IVC. Collaterals feeding into the pulmonary veins have been described. The presence of portosystemic anastomosis usually implies PH, although occasionally, if the collateral circulation is extensive, portal pressure may decrease. Conversely, PH of short duration can exist without demonstrable collateral circulation. The collateral pathways in extrahepatic venous obstruction depend on the site of obstruction. In the absence of liver disease, with splenic vein occlusion, portal-portal collateral pathways develop over gastric veins (splenic, short gastric, coronary portal veins) and omental veins (splenic, gastroepiploic or arch of Barkow, superior mesenteric portal veins). In superior mesenteric vein obstruction, collaterals develop via the pancreaticoduodenal or cystic veins. In portal vein occlusion, collaterals develop via peribiliary venous plexus, via veins in the hepatoduodenal ligament, and in the hepatic hilus. Clinical DetailsEtiology of PH The causes of PH are many and can be subdivided into diseases causing prehepatic, hepatic, or posthepatic PH. The causes include alcoholic cirrhosis, schistosomiasis, hepatocellular carcinoma, BCS, hepatoveno-occlusive disease, hepatitis and other chronic liver diseases, and the many causes of PVT. Causes of PH include the following:
Clinical presentation PH is accompanied by 3 major complications, as follows:
Hepatic encephalopathy is devastating and usually results from gastrointestinal bleeding, which is life threatening. The development of hepatic encephalopathy in patients with portal hypertension is most often related to the size of the portosystemic anastomosis. Splenoportal shunts are usually large. Cirrhosis of the liver is the most common cause of PH. Stigmata of cirrhosis, including jaundice, spider nevi, caput medusae, and palmar erythema may be associated with signs of PH. Preferred ExaminationPlain radiographs are not often obtained in PH, but because most hospitalized patients undergo chest radiography, radiologists need to be aware of abnormalities that may be found in PH. Calcification in the distribution of the portal vein on a plain abdominal radiograph may indicate PH. An upper GI tract barium series is often performed for the detection of esophageal varices. US techniques such as duplex US or spectral Doppler imaging and CDI or power Doppler imaging are the modalities of choice in the evaluation of the liver and PH. These techniques are noninvasive, rapid, and highly sensitive and specific. Angiographic techniques such as SP, transhepatic portography, transumbilical catheterization, transjugular catheterization, wedge hepatic venography, and arterial portography are invasive. However, they are much more specific examinations for evaluation of PH hypertension, and they are indicated when definitive surgery or radiologic intervention is contemplated. The use of angiographic techniques is declining because of noninvasive imaging techniques such as US, CT and computed tomography angiography (CTA), and magnetic resonance angiography (MRA) are now available. These techniques are quickly improving and will further limit the use of angiographic methods. SP and transumbilical catheterization is rarely performed. Arterial portography (indirect portography) and wedge hepatic venography with manometry is indicated prior to surgical portacaval shunt placement. Carbon dioxide wedge hepatic venography is the most commonly used to visualize the portal vein before portal vein puncture for a transjugular intrahepatic portosystemic shunt (TIPS) procedure. TIPS is a radiology-guided creation of a shunt between the portal and hepatic veins in the liver by using a percutaneous transjugular approach. Because of its proven safety and effectiveness, the TIPS has largely replaced surgical decompressive shunt procedures. Limitations of TechniquesPlain radiographs are usually not indicated as an investigation for PH. Most plain radiographs are obtained for other reasons, and signs of PH are detected incidentally. Therefore, plain radiographs are of limited value. Duplex US is a sensitive technique for detection of PH in addition to other important features. When respiratory variation in the size of the portal, splenic, and superior mesenteric veins does not occur or when it is less than 20%, PH may be diagnosed with a sensitivity of 80% and a specificity of 100%. When the patient has bleeding varices unresponsive to endoscopic sclerotherapy or when he or she has intractable ascites, a TIPS procedure is indicated. This is performed after portal vein patency is documented at duplex US. DIFFERENTIALSSection 3 of 11
Budd-Chiari Syndrome Cirrhosis Congestive Heart Failure Constrictive Pericarditis Portal Vein Thrombosis Other Problems to Be ConsideredVeno-occlusive disease
RADIOGRAPHSection 4 of 11
FindingsPlain radiographic findings
Barium study findings of esophageal varices
Barium study findings of varices in other parts of the gastrointestinal tract Gastric antral and duodenal varices are sometimes seen, usually in association with gastric fundal and esophageal varices.
Degree of ConfidencePlain radiography is not sensitive in the diagnosis of PH. With good operator technique, barium examination can depict more than 90% of varices. The rate of detection with barium study has been reported to be 65-89%. False Positives/NegativesOther causes of calcification overlying the liver may mimic portal vein calcification. One example is hepatic arterial calcification.
CT SCANSection 5 of 11
FindingsComputed tomography CT has been used to assess disease in patients with PH.
CT angiography CTA is an exciting new application of helical CT. The speed of helical CT allows the maintenance of a higher concentration of intravenous contrast medium, particularly through the arterial enhancement phase, with the capability of 3-dimensional reconstruction. Both peripheral intravenous injections of contrast material and CT arterial portography have been used as a basis for CTA. CTA has shown great promise in the evaluation of hepatic vessels before liver resection. It provides preoperative surgical information regarding the segmental location of liver tumors, the segmental venous anatomy, and significant arterial anomalies if present. The value of CTA in PH remains unclear. Degree of ConfidenceA diagnosis of PH frequently is based on the demonstration of signs of cirrhosis. Splenomegaly and ascites are demonstrated readily on CT; however, CT findings in cirrhosis are highly variable. In some patients, the liver is of nonuniform attenuation, and hypoattenuating components probably represent residual foci of infiltration. Often, the attenuation of a cirrhotic liver is homogeneous and within the reference range. In the absence of obvious abnormalities of size and shape, the liver may appear entirely normal on CT scans. Nonenhanced CT is necessary when the cirrhotic liver is imaged for the identification of confluent fibrosis. Confluent fibrosis characteristically demonstrates low attenuation, which tends to become isoattenuating or minimally hypoattenuating on CT following intravenous contrast enhancement. Thus, confluent fibrosis is frequently missed if only contrast-enhanced CT is used. Collateral veins are occasionally seen in the peritoneal cavity, retroperitoneum, abdominal wall, and mediastinum. CT lacks the dynamic capability of angiography in demonstrating the exact sites of portosystemic shunts and the feeding vessels. False Positives/NegativesIn patients with cirrhosis, CT scans may appear entirely normal. Other causes of diffuse liver disease, such as splenomegaly and ascites, must be considered. MRISection 6 of 11
FindingsMagnetic resonance angiography
Magnetic resonance imaging In patients with elevated creatinine levels who cannot undergo a CT scan with intravenous contrast enhancement, MRI with gadolinium enhancement can often be performed (see warning below). These contrast-enhanced images are typically breath-hold fast spoiled gradient-echo sequences, which can be dynamically obtained in both the arterial and portal venous phases. Gadolinium-based contrast agents (gadopentetate dimeglumine [Magnevist], gadobenate dimeglumine [MultiHance], gadodiamide [Omniscan], gadoversetamide [OptiMARK], gadoteridol [ProHance]) have recently been linked to the development of nephrogenic systemic fibrosis (NSF) or nephrogenic fibrosing dermopathy (NFD). For more information, see the eMedicine topic Nephrogenic Fibrosing Dermopathy. The disease has occurred in patients with moderate to end-stage renal disease after being given a gadolinium-based contrast agent to enhance MRI or MRA scans. As of late December 2006, the FDA had received reports of 90 such cases. Worldwide, over 200 cases have been reported, according to the FDA. NSF/NFD is a debilitating and sometimes fatal disease. Characteristics include red or dark patches on the skin; burning, itching, swelling, hardening, and tightening of the skin; yellow spots on the whites of the eyes; joint stiffness with trouble movingor straightening the arms, hands, legs, or feet; pain deep in the hip bones or ribs; and muscle weakness. For more information, see the FDA Public Health Advisory or Medscape. Degree of ConfidenceMRI does not offer an advantage over CT in the diagnosis of cirrhosis; however, morphologic changes identified on US or CT are clearly depicted on MRI. One advantage of MRI over CT is the characterization of regenerative nodules in a cirrhotic liver. MRA may offer a noninvasive non–operator dependent evaluation of the portal venous system; however, the exact sensitivity and specificity still need to be determined. ULTRASOUNDSection 7 of 11
Findings
Portal vein waveforms The portal vein typically shows continuous forward flow with minor modulation caused by respiration and transmitted arterial pulsation. The rate of blood flow is greatest at the center of the vessel and is least at its margins; therefore, the average flow across a segment of the vessel is used to overcome the internal variation resulting from respiration and transmitted cardiac pulsation. The time-averaged velocity usually is on the order of 12-14 cm/s in adults. Flow within the portal vein changes rapidly in response to eating. Blood flow to the small bowel begins to increase within 2 minutes of taking the first mouthful of food. The time-averaged blood flow velocity in the portal vein may increase to 25 cm/s after a meal, and with minor increase in vessel diameter, the flow volume may increase 4-5 times. Most patients with mild hepatic parenchymal disease have normal portal venous blood flow. As hepatic disease becomes more severe, the first detectable flow abnormality is a reduction in the level of increase in flow seen after a meal. Then, the splenic and superior mesenteric veins may begin to distend, and the change in vessel caliber that is seen normally with respiration is lost. In severe hepatic parenchymal disease, portal venous blood flow is reduced, and a rough correlation is noted between the degree of reduction in portal flow velocity and the severity of hepatic parenchymal disease (providing that studies are performed in strictly fasting patients). As portal venous flow is compromised further, forward flow may be seen only during systole, with reversed flow occurring during diastole. Eventually, flow within the portal vein may be reversed continuously, but the rate and direction of flow may vary from day to day, particularly in patients with acute exacerbation of chronic liver disease. Therefore, serial examinations provide a better picture than single scans. Clearly reduced portal flow velocity is associated with increased risk of thrombosis. Portal venous shunts Percutaneous creation of a shunt between the portal and hepatic veins with TIPS is becoming increasingly common as a treatment for PH. Doppler US may be used to assess patency and show the direction of flow within the portal vein and shunt. If the walls of an artificial shunt prevent direct analysis of blood flow within it, an analysis of flow at the ends of the shunt usually allows adequate assessment of shunt function. Surgically created shunts include portocaval (end or side of main portal vein to IVC), mesocaval, and splenorenal shunts (Warren shunt). Mesocaval and splenorenal shunts are used more frequently to maintain portal venous patency for transport than for other purposes. CDI is valuable for the evaluation of shunts. US evaluation of PH The diameter of the portal vein is measured with the patient in a supine position, in quiet respiration, and with the patient fasting for a minimum of 4 hours. Measurements are made at the point at which the portal vein crosses the IVC. In an individual without PH, the diameter of the portal vein is 13 mm or 16 mm during deep inspiration. Under standard conditions, measurements greater than 13 mm indicate PH with a specificity of 100% but a low sensitivity of 45-50%. Sensitivity can be increased to 81% by measuring splenic vein and superior mesenteric vein diameters. An increase in diameter by 20-100% during deep inspiration is normal. An increase of less than 20% is associated with PH. The differential diagnosis of a dilated portal vein includes PH splenomegaly (whatever the cause), acute PVT, and postprandial increase in portal vein diameter. Portal flow direction and velocity Usually, blood flow in the portal vein is hepatopetal (toward the liver) during the entire cardiac cycle. The mean velocity is 15-18 cm/s and varies with cardiac cycle. In PH, velocity fluctuations disappear, resulting in continuous flow. With a further increase in portal venous pressure, the blood flow direction becomes to-and-fro (biphasic), and finally, the direction is reversed (hepatofugal). Differential diagnosis of hepatofugal portal venous flow includes PH, BCS, side-to-side portocaval shunts, surgical or spontaneous splenorenal shunts with cirrhosis, and tricuspid regurgitation (tricuspid flow reversal). Differential diagnosis of portal venous flow reversal includes severe PH, tricuspid regurgitation, and congestive heart failure. The differential diagnosis of reversal of hepatofugal-to-hepatopetal portal flow includes eating and the use of drugs that increase portal flow. Static flow without Doppler signal occurs occasionally. Pulsatile portal vein flow A pattern similar to that seen in patients with impaired right heart function occasionally can be seen in patients with cirrhosis and/or PH. Patients with right-sided cardiac dysfunction with pulsatile portal venous flow invariably have abnormal liver function. The differential diagnosis of pulsatile portal venous flow includes tricuspid regurgitation, aortic–right atrial fistula, fistula between the portal vein and hepatic vein, PH, and congestive heart failure. Rarely, it may be a false-positive finding. Decreased volume flow in the portal vein In mild-to-moderate PH, the volume of flow in the portal vein is maintained. A reduction in volume flow occurs with advanced cirrhosis when intrahepatic obstruction to portal flow is severe as indicated by hepatofugal flow and extensive portosystemic collaterals. Congestive Index PH may be recognized by using the congestive index, in which the ratio of the portal vein (in units of square centimeter) is divided by the mean portal flow velocity (in units of centimeter per second). This ratio reflects the physiologic changes that occur in PH, ie, portal vein dilatation associated with diminished flow velocity. In individuals without PH, the ratio should not exceed 0.7. Splenomegaly The size of the spleen is not well correlated with the level of PH; however, if splenomegaly is absent, PH is unlikely. The spleen is best measured in the coronal plane. In the midaxillary line, a cephalocaudal measurement greater than 13 cm suggests enlargement. Splenic interface sign Linear reflective channels are observed in the splenic parenchyma in a variable number of patients with PH. Channels may be explained by dilatation of intrasplenic venous sinuses with increased collagen in the walls and by periarterial fibrosis. The pathologic changes are known to occur in PH. The splenic interface sign seldom is found in splenomegaly unrelated to PH. The vascular nature of channels is readily confirmed by using CDI. Ascites Uncomplicated PH usually does not cause ascites. Usually, ascites occurs secondary to underlying liver diseases with liver cell failure. Arterialization of hepatic blood supply Hepatic arteries are enlarged and usually have aliased frequency shifts compared with those of normal hepatic arteries. The arteries also appear tortuous. As portal venous flow to the liver decreases, arterial flow increases. Increased arterial flow occurs with the development of large collaterals and hepatopetal flow. The differential diagnosis of enlarged hepatic artery includes an occluded or interrupted portal vein, a surgical portosystemic shunt, reversal of flow in the portal vein, parenteral feedings in newborns, hereditary hemorrhagic telangiectasia, cirrhosis or hepatic diseases associated with alcohol, vascular hepatic tumors, and primary hepatic artery dissection. Portosystemic venous collaterals Demonstration of portosystemic venous collaterals (PVCs) indicates without doubt that PH exists. US findings of PVCs are as follows:
Banti syndrome Banti syndrome, or noncirrhotic idiopathic PH, is a common cause of PH in India and Japan but is rare in the United States and Europe. The syndrome is characterized by signs of PH, but liver function test results tend to remain normal. Hepatic wedge pressure readings are usually normal or slightly elevated. Signs of hypersplenism are often present. US shows a normal-appearing liver; patent hepatic veins; and a patent portal vein, which may be associated with multiple portosystemic collaterals. Portal venous thrombosis PVT is recognized with increasing frequency on US images. Reduced portal blood flow resulting from hepatic parenchymal disease and abdominal sepsis are the primary causes. Transient PVT is also recognized with increasing frequency, in part because of the large increase in the use of US in evaluating patients with abdominal inflammation, such as appendicitis. Tumor within the portal vein may appear identical to thrombosis, but it is far less common. Tumor within the portal vein is most frequently related to a hepatocellular carcinoma, which gives rise to serpiginous filling defects in the portal venous luminal flow, but it usually persists around the tumor without complete occlusion. Adults with acute PVT secondary to abdominal sepsis completely recover with vessel recanalization after successful treatment of underlying sepsis. In children, the portal vein may recanalize by developing multiple small collateral channels, which are seen as a partly echogenic band of small vessels running to the porta hepatis. These show reduced flow velocity of 2-7 cm/s. Nonvisualization of the portal vein is strongly suggestive of occlusion. Then, the portal vein may be seen as a band of high-level echoes at the porta hepatis. Causes of PVT include idiopathic causes, malignancy (hepatocellular carcinoma, cholangiocarcinoma, pancreatic, and stomach carcinoma), trauma (which maybe iatrogenic, eg, umbilical vein catheterization), and abdominal sepsis (pancreatitis, perinatal sepsis, omphalitis, appendicitis, diverticulitis, cirrhosis), especially in younger individuals. On sonograms, clot exhibits variable echogenicity, and it may be hypoechoic or anechoic if it is recently formed. Conversely, patent vessels may show increased intraluminal echogenicity because of artifact or erythrocyte rouleaux formation. In isolation, increased or decreased echogenicity in the lumen of the portal vein is not sufficient to diagnose or exclude PVT. PVT eliminates the venous flow signal typically obtained from the lumen of the portal vein during pulsed or color flow Doppler imaging, and it may show flow around a thrombus that partially occludes the vein. However, if flow is sluggish, the Doppler signal may not be detected. Color flow may be demonstrated in other small collaterals. Incomplete occlusion (common in neoplastic invasion) or thrombolytic recanalization may occur. These cannot be differentiated by using US. A cavernous malformation may be noted vide infra. Hepatopetal flow may be demonstrated and spontaneous shunts visualized (splenorenal). US may demonstrate portosystemic collaterals and cause may be identified, such as hepatocellular carcinoma, metastases, cirrhosis, and pancreatic neoplasms. Incidence of PVT is said to be low in PH, but it is associated with sclerotherapy. The string sign, or thickening of the portal vein with narrowing of its lumen interpreted as a portal phlebitis, is considered a precursor of PVT in patients with acute pancreatitis. The portal vein thrombus may become calcified. Cavernous transformation of the portal vein Cavernous transformation occurs with long-standing PVT (19%) when numerous multiple collateral vessels develop around the occluded portal vein, giving the appearance of vermiform tubular structures at the porta hepatis. Application of color-pulsed Doppler imaging shows blood flow in the periportal collaterals around the thrombosed portal vein. Cavernous transformation of the portal vein has been recorded as appearing to be a subhepatic spongelike mass. This appearance also has been reported in patients with pancreatic hemangiosarcoma. Bile duct varices, also called the pseudocholangiocarcinoma sign, are not infrequently observed during endoscopic retrograde cholangiopancreatography. In PH, they result from cavernous transformation of the portal vein. Findings show that the sign may disappear after a TIPS procedure. Assessment of TIPS TIPS are shunts placed percutaneously via the jugular vein. TIPS are becoming popular as a definitive procedure for decompressing the portal venous system or as a prelude to liver transplantation. Doppler US is a sensitive and relatively specific means of evaluating TIPS malfunction. US evaluation of the shunt is usually performed within 24 hours after shunt placement to establish baseline velocities within the portal vein, hepatic vein, and shunt. Follow-up studies are usually performed at 3-month intervals unless the clinical setting dictates a more emergent examination. The primary object of Doppler study of a TIPS is to document flow in the shunt and to demonstrate stenosis. The accuracy of Doppler US in shunt malfunction depends on several US parameters, which include the peak shunt velocity, distal shunt velocity, and antegrade flow in the left and right portal veins. Flow velocities in the portal vein may double when compared with the preoperative velocities in a successful TIPS placement. Direct observation of shunt thrombosis is possible with duplex or color Doppler US. Echo-enhanced color Doppler US can also be helpful in the assessment of TIPS. Complications of TIPS detectable on US images include the following:
Degree of ConfidenceDemonstration of portosystemic shunts is a specific sign of PH. Umbilical vein collateral flow is an important feature of PH because it has a specificity of a 100%. In individuals without PH, the caliber of portal, splenic, and superior mesenteric veins show significant variation during respiration. When respiratory variation does not occur or when it is slight (<20%), PH can be diagnosed with a sensitivity of 80% and a specificity of 100%. A portal vein diameter greater than 13 mm is specific for PH, but it is not a sensitive indicator of PH. False Positives/Negatives
ANGIOGRAPHYSection 8 of 11
FindingsAngiographic evaluation of the portal venous system may be performed. Splenoportography Recently, because of the use of alternative imaging methods, the use of SP has declined considerably after having a primary role in the investigation of cirrhosis and PH for several years. However, restricted indications remain for the procedure. Even with the available methods of direct or indirect visualization of the portal vein, much of the information necessary to evaluate cirrhosis or PH can be obtained by using SP. Splenic pulp measurement provides an accurate reflection of the portal venous pressure, both in hepatic and prehepatic causes of PH. An intravenous injection of radiographic contrast medium into the splenic pulp outlines the portosystemic collaterals (ie, splenic and portal veins) and provides a good demonstration of the intrahepatic portal radicles and enables an assessment of the rapidity of washout of the vessels in a hepatopetal direction. With reversal of flow within the portal vein resulting from severe PH, the splenic and portal veins are not visualized, and the contrast outflow tract is via gastroesophageal collaterals. With splenic thrombosis/PVT, not only is the site of the obstruction evident, but portal-portal collateral veins, which regularly develop, are demonstrated as well. Contraindications to SP include coagulation defects, platelet count less than 50,000, ascites, an uncooperative patient, and splenic pathology (splenic mass lesions). To perform SP, the skin over the left side of the thorax and abdomen overlaying the spleen is prepared with an antiseptic after the spleen is localized. Historically, the spleen was localized by using fluoroscopy and palpation and percussion, but currently, localization is more commonly performed by using US. A skin bleb is raised near the lower pole of the spleen in mid respiration, and the soft tissues are infiltrated with local anesthetic down to the peritoneum. The entry site of the needle usually is the 9th or 10th intercostal space in the midaxillary line. The needle is directed in a cephalic direction toward the splenic hilum. A nick is made at site of the needle puncture, and a track is made into the soft tissues with a 12-gauge needle, which facilitates the placement of the SP needle. The SP needle is a 14-gauge 6-inch-long polyethylene sheathed needle. With patient breath hold in mid respiration, the sheathed needle is introduced towards the direction of the splenic hilum, and the stilette is withdrawn, leaving the sheath in place. The patient is instructed to take shallow respirations during the examination. If the spleen has been entered accurately, blood flows back via the sheath. Then, the sheath is connected to a spinal pressure manometer filled with saline, and the splenic pulp pressure is measured. The sheath is taped to the patient's side, and a test injection is made by using 5 mL of contrast medium. When a sheath is placed correctly, contrast medium spreads into the splenic parenchyma, providing an uneven splenogram that rapidly drains into the splenic vein. With a subcapsular placement, the contrast agent is viewed as a homogeneous collection that spreads slightly as the agent is injected. With subcapsular injection, the needle is withdrawn completely, and a fresh attempt is made to place the needle correctly. With the sheath correctly placed, a pump injection is performed by using 40 mL of 75% contrast at a rate of 10 mL/s. The injection is usually painless; discomfort and shoulder pain may occur with subcapsular injection. After the procedure is complete, the needle tract is plugged with thromboembolic material, such as Gelfoam or Ivalon. Complications of the procedure include hemorrhage, contrast agent extravasation, puncture of other organs, splenic hematomas, and capsular rupture. Capsular rupture may require emergency laparotomy and splenectomy. In addition to splenectomy, splenic artery embolization may be used to stop bleeding. Indications for SP include the following:
In PH, the following findings may be noted with SP:
Carbon dioxide SP Carbon dioxide as a contrast agent for SP has been recently performed by using a 22- or 25-gauge needle (exploiting low viscosity of the gas). This technique is less traumatic than others, and it has been effective in visualizing the portal venous system. The hope is that the difference in the collateral venous filling patterns is significant as carbon dioxide fills veins in the nondependent sites while contrast material flows along the dependent sites. Contrast-enhanced SP has been infrequently used in the United States. Transhepatic portography Percutaneous transhepatic portography (PTP) uses the same technique as percutaneous cholangiography. The portal vein is punctured directly and replaced by a guidewire/catheter, and contrast material is injected into the splenic vein and/or the superior mesenteric vein, depending on the clinical setting. PTP is an easy and quick procedure. As a result of the straight course of the catheter through the liver substance, catheterization of several tributaries is possible, but the distance between the cutaneous entrance of the catheter and the liver makes catheter manipulation difficult. The few reported complications mostly result from nontarget organ puncture (gallbladder, pleura) and intra-abdominal hemorrhage. With US guidance, the incidence of nontarget organ puncture is expected to decrease. Transcatheter obliteration of esophageal varices with various embolic agents is possible via transhepatic catheter placement, but this is not a procedure to be followed by suitable surgical procedure. Transcatheter obliteration should not be used as an elective procedure; even in an acute setting, hemostasis is best attempted with other methods. Transumbilical catheterization Transumbilical catheterization requires a surgical procedure in which a transverse incision is made 3-5 cm above the umbilicus, and the umbilical vein is catheterized. Complications are few, but the procedure is difficult and time consuming. With so many noninvasive procedures currently available, the procedure is seldom indicated. Transjugular catheterization The transjugular approach to the portal vein first was described by Rösch et al in 1969. Since that time, the technique has improved and currently is used more for therapeutic applications, such as the establishment of a TIPS. Wedged hepatic venography When a catheter is placed in a small hepatic vein via the IVC or jugular vein, pressures can be measured either with a transducer or with a saline manometer. In patients with sinusoidal or postsinusoidal portal venous obstruction, as in cirrhosis, pressure measured in this way accurately reflects the total portal pressure. The wedged hepatic venous pressure is the same as the splenic pulp pressure measured by using SP. Normal portal pressure levels measured in this way are 40-150 mm of saline. Pressures above 150 mm of saline indicate PH. Two components contribute to PH. The first is intrahepatic resistance to portal venous flow, and the second is transmitted pressure from the IVC. In addition, IVC pressures are measured, and the corrected sinusoidal pressure is derived by subtracting the IVC pressure from the wedged hepatic pressure. The concept of a corrected sinusoidal pressure is useful clinically because it reflects the true status of the liver disease responsible for development of portosystemic shunts and variceal bleeding. Corrected sinusoidal pressure readings of as high as 100 mm of saline are considered normal. Although corrected sinusoidal pressure makes the most significant contribution to variceal bleeding in patients with cirrhosis, the total pressure usually contributes to bleeding from esophageal varices. Thus, a patient with both cirrhosis and congestive heart failure may bleed from esophageal varices because of a temporarily increased central venous pressure; conversely, esophageal bleeding may cease when the central venous pressure is decreased. Typically, patients with cirrhosis do not bleed from varices with portal venous pressures of 200-250 mm of saline. Patients with cirrhosis who bleed at pressures lower than 200 mm of saline almost always bleed from an alternative source. Arterial portography Arterial portography (AP) is currently the preferred method for evaluating the portal venous system because it is less invasive and has a lower complication rate. AP involves the indirect opacification of the portal venous system with the injection of contrast material into the celiac axis (delayed images outline the splenic, gastric, and portal veins) or into the superior mesenteric artery (outlining superior mesenteric and portal veins). The 3 major indications for AP include the following:
Preparation and contraindications for AP are identical to those of standard conventional angiography. Selective catheters are used to cannulate the appropriate artery. In a superior mesenteric artery injection, the tip of the catheter is placed such that it opacifies all the branches with contrast medium. Before delivery of the contrast agent, administration of a vasodilator (tolazoline, papaverine, nitroglycerin) improves opacification of the portal vein. Manual or digital subtraction imaging improves resolution. If digital subtraction is used, administration of an anticholinergic drug prior to filming reduces bowel movement. Left gastric artery injection consistently demonstrates esophageal varices. AP findings in PH include the following:
Degree of ConfidenceSP is a fairly accurate method of outlining the portal venous system and the portosystemic communications in PH; for this, SP remains the criterion standard. Diagnostic modalities such as US, CT, and MRI have reduced the diagnostic importance of arteriography. The major role of angiography is in mapping the vascular anatomy prior to surgery and in guiding the transcatheter treatment of liver tumors. In celiac-axis and superior angiography, the venous phase provides sufficient detail to render direct portography unnecessary in most patients. INTERVENTIONSection 9 of 11
Gastrointestinal bleeding from esophageal varices remains the most life-threatening condition resulting from PH. This is usually secondary to cirrhosis. The 30-day mortality rate approaches 30%, and rebleeding and death are common within 1 year. Surgery has failed to reduce the mortality rate. Endoscopic sclerotherapy has emerged in recent years as the most popular treatment. The goal is to arrest active bleeding by producing intravariceal thrombosis or extraluminal fibrosis around the varices. Various sclerosants are used. Percutaneous transhepatic coronary vein embolization is infrequently performed because of the high incidence of recurrent bleeding secondary to the development of new collaterals. Instead, most patients with variceal bleeding unresponsive to endoscopic sclerotherapy or banding undergo a TIPS procedure, during which the coronary vein may be embolized if gastroesophageal varices continue to fill after placement of a TIPS. The technique used most often is PTP (see Angiography). The agent that provides the most effective long-term occlusion is large strips of compressed Gelfoam soaked in 3% sodium tetradecyl sulfate. The procedure may provide an alternative in arresting acute variceal bleeding not responsive to vasopressin or other medical methods. Transhepatic embolization may improve the patient's general status enough to allow surgeons to perform elective shunt surgery. Medical/Legal Pitfalls
MULTIMEDIASection 10 of 11
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