Magnetic resonance imaging in the evaluation of the portal venous system.

Magnetic resonance (MR) imaging is used in assessing the portal venous system through qualitative and quantitative methods. Magnetic resonance angiography can be performed using time-of-flight or phase-contrast techniques. Time-of-flight techniques (which use gradient echo images to display bright blood or spin echo images to display black blood) are relatively standardized and commercially available. These techniques are used to display liver morphology, portal vein patency, portal venous collaterals, and surgically created portosystemic shunts. Magnetic resonance is equivalent to angiography in the detection of varices, according to a preliminary study. Time-of-flight flow imaging using gradient echo techniques (in which a thrombus appears as absence of bright signal in the portal vein) and spin-echo techniques (where thrombus appears as a bright signal) can become combined to increase specificity for diagnosis of portal vein thrombosis. Phase-contrast techniques provide flow information based on phase shifts induced by flow through magnetic gradients. Phase-contrast angiography is less widely available than time-of-flight angiography. However, phase-contrast methods allow imaging of very slow flow that is not possible using time-of-flight methods. Quantitation of flow is possible, both with time-of-flight techniques using bolus tracking and with phase-contrast techniques using quantitative measurement of phase shifts. Calculations of flow velocity correlate well with Doppler ultrasound estimations, MR flow quantitation does not, at present, rival ultrasound in terms of cost or availability. However, MR is not limited by obesity or overlying bowel gas which can prevent adequate ultrasound evaluation.(ABSTRACT TRUNCATED AT 250 WORDS)     

Hepatic radionuclide angiography and Doppler ultrasonography in the detection and assessment of vascular disturbances in the portal system

BACKGROUND/AIMS: The aim of the study was evaluation of the morphology of the blood vessels, blood flow velocity and direction with Doppler ultrasound (D-US) and correlation with the relative liver parenchymal perfusion assessed by hepatic radionuclide angiography (HRA). METHODOLOGY: Real-time, D-US and HRA were performed in 108 patients. RESULTS: In patients with portal venous aneurysm, hepatopetal blood flow was increased, while portal perfusion did not differ from controls. In portal hypertensive patients, D-US detected dilatation of the portal system veins, with decreased blood flow. In comparison to the portal perfusion in controls and portal venous aneurysm, values were significantly (p < 0.01) lower in chronic active hepatitis and liver cirrhosis and differed between themselves (p < 0.01). In the groups of cirrhotic patients with esophageal varices, sclerosed esophageal varices, recanalized umbilical vein, partial portal thrombosis and cavernous portal vein with hepatofugal, hyperkinetic or slow blood flow, and very low velocities beside the thrombi, portal perfusion was lower (p < 0.01) than in controls, portal venous aneurysm, chronic active hepatitis and liver cirrhosis without collaterals. In complete thrombosis, minimal collateral flow was found with D-US, while HRA proved no portal supply. CONCLUSIONS: D-US and HRA are complementary for the estimation of various liver vascular disorders.     

Diagnóstico y tratamiento de la trombosis portal en la cirrosis hepática

Improved imaging techniques and the routine use of color Doppler ultrasound in the follow-up of patients with liver cirrhosis has increased diagnosis of portal vein thrombosis (PVT) in these patients. The extension of PVT should be evaluated with computed tomography angiography or magnetic resonance angiography. The natural history of PVT in cirrhosis and its impact on liver disease is unknown but it seems clear that PVT could increase the morbidity and mortality associated with liver transplantation and can even be a contraindication to this procedure when the thrombus extends to the superior mesenteric vein. Anticoagulation is a relatively safe and effective treatment in achieving recanalization of the splenoportal axis or in preventing progression of thrombosis and is therefore frequently used. The use of transjugular intrahepatic portosystemic shunts (TIPS) is reserved for patients unresponsive to anticoagulation or in those with severe complications of portal hypertension.     

Portal venous hemodynamics in hepatocellular carcinoma. Effects of hepatic artery embolization

Portal hemodynamics were studied in 55 patients with hepatocellular carcinoma in comparison with 41 normal subjects, using the duplex system that consists of an electronic sector scanner and a pulsed Doppler velocitometer. Changes of portal hemodynamics after transcatheter hepatic artery embolization were also investigated in 15 of the patients with hepatocellular carcinoma. The duplex system showed that 9 of the 55 had no Doppler signal in the portal trunk, suggesting portal vein thrombosis, 2 had hepatofugal flow in the portal trunk indicative of arterioportal shunts, and 44 had hepatopetal flow in the portal trunk. One of the 9 patients with no significant portal venous flow showed hepatopetal flow in collateral veins at the porta hepatis, suggesting cavernous transformation of the portal vein. All of these ultrasound findings were confirmed by subsequent celiac-mesenteric angiography. In 44 of the 55 patients there was no tumor invasion in the portal trunk, and portal venous flow was found to be close to that of normal subjects regardless of the stage or size of tumor, and tumor invasion into relatively large portal branches. After transcatheter hepatic artery embolization, portal venous flow was increased, even on the next day, and it remained increased for at least 2 wk. Thus, the duplex system is useful to study qualitative and quantitative changes of portal hemodynamics in hepatocellular carcinoma. Our observations suggest that the portal venous flow is kept relatively constant by some homeostatic mechanism even in advanced hepatocellular carcinoma until the tumor invades into the portal trunk, and that it increases when hepatic arterial flow is occluded.     

Intrahepatic Portosystemic Venous Shunt: Diagnosis by Color Doppler Imaging

Intrahepatic portosystemic venous shunt is a rare clinical entity; only 33 such cases have been reported. It may be congenital, or secondary to portal hypertension. Five patients with this disorder are presented, each of whom was diagnosed by color Doppler imaging, including waveform spectral analysis. One patient with clinical evidence of cirrhosis and portal hypertension had episodes of hepatic encephalopathy and elevated blood levels of ammonia. This patient had a large tubular shunt between the posterior branch of the portal vein and the inferior vena cava. Shunts of this type are considered to be collateral pathways which develop in the hepatic parenchyma as a result of portal hypertension. The other four patients had no evidence of liver disease, and all four evidenced an ancurysmal portohepatic venous shunt within the liver parenchyma. Shunts of this type are considered congenital. The diagnosis of intrahepatic portosystemic venous shunts was established by color Doppler imaging, which demonstrated a direct communication of color flow signals between the portal vein and hepatic vein, in addition to the characterization of the Doppler spectrum at each sampling point from a continuous waveform signal (portal vein) to a turbulent signal (aneurysmal cavity), and finally, to a biphasic waveform signal (hepatic vein). As demonstrated by the five patients, color Doppler imaging is useful in the diagnosis of an intrahepatic portosystemic hepatic venous shunt, and the measurement of shunt ratio may be useful in the follow-up and determining the therapeutic option.     

Embolization of splenorenal shunt associated to portal vein thrombosis and hepatic encephalopathy

Hepatic encephalopathy (HE) is a cognitive disturbance characterized by neuropsychiatric alterations. It occurs in acute and chronic hepatic disease and also in patients with portosystemic shunts. The presence of these portosystemic shunts allows the passage of nitrogenous substances from the intestines through systemic veins without liver depuration. Therefore, the embolization of these shunts has been performed to control HE manifestations, but the presence of portal vein thrombosis is considered a contraindication. In this presentation we show a cirrhotic patient with severe HE and portal vein thrombosis who was submitted to embolization of a large portosystemic shunt. Case report: a 57 years-old cirrhotic patient who had been hospitalized many times for persistent HE and hepatic coma, even without precipitant factors. She had a wide portosystemic shunt and also portal vein thrombosis. The abdominal angiography confirmed the splenorenal shunt and showed other shunts. The larger shunt was embolized through placement of microcoils, and the patient had no recurrence of overt HE. There was a little increase of esophageal and gastric varices, but no endoscopic treatment was needed. Since portosystemic shunts are frequent causes of recurrent HE in cirrhotic patients, portal vein thrombosis should be considered a relative contraindication to perform a shunt embolization. However, in particular cases with many shunts and severe HE, we found that one of these shunts can be safely embolized and this procedure can be sufficient to obtain a good HE recovery. In conclusion, we reported a case of persistent HE due to a wide portosystemic shunt associated with portal vein thrombosis. As the patient had other shunts, she was successfully treated by embolization of the larger shunt.     

Transhepatic catheter-directed thrombolysis for portal vein thrombosis after partial splenic embolization in combination with balloon-occluded retrograde transvenous obliteration of splenorenal shunt

A 66-year-old woman underwent partial splenic embolization (PSE) for hypersplenism with idiopathic portal hypertension (IPH). One week later, contrast-enhanced CT revealed extensive portal vein thrombosis (PVT) and dilated portosystemic shunts. The PVT was not dissolved by the intravenous administration of urokinase. The right portal vein was canulated via the percutaneous transhepatic route under ultrasonic guidance and a 4 Fr. straight catheter was advanced into the portal vein through the thrombus. Transhepatic catheter-directed thrombolysis was performed to dissolve the PVT and a splenorenal shunt was concurrently occluded to increase portal blood flow, using balloon-occluded retrograde transvenous obliteration (BRTO) technique. Subsequent contrast-enhanced CT showed good patency of the portal vein and thrombosed splenorenal shunt. Transhepatic catheter-directed thrombolysis combined with BRTO is feasible and effective for PVT with portosystemic shunts.     

Spontaneous regurgitation of portal blood flow normalized by meal intake in a patient with alcoholic liver cirrhosis

We report a case with spontaneous regurgitation of portal blood flow (SRPBF) that was normalized by meal intake. A 41-year-old man with long-term alcohol abuse was admitted with a chief complaint of general fatigue. He was diagnosed as having alcoholic liver cirrhosis since his laboratory tests showed the abnormal liver function. Dynamic computed tomography detected numerous portosystemic shunts. Hepatic arterial portography showed the portal vein was narrow and irregular. Color Doppler imaging portrayed the direction of the blood flows in the branches of the portal vein to be retrograde. However, 30 min after meal intake on the same day, color Doppler study showed the direction of the blood flow in the first branch of right and left portal vein became normal. Color Doppler imaging is a useful technique to detect SRPBF and hemodynamic change in portal venous system after meal intake in patient under a completely physiologic condition.     

Time-resolved 3D cine phase-contrast magnetic resonance imaging (4D-flow MRI) can quantitatively assess portosystemic shunt severity and confirm normalization of portal flow after embolization of large portosystemic shunts

Diagnosis and severity assessments of portosystemic shunts (PSSs) are important because the pathology sometimes results in severe hepatic encephalopathy, which can be treated almost completely by shunt embolization. At present, morphological assessment of PSS is performed mainly by computed tomography, and ultrasound is used for blood flow assessment. In two cases of PSS-related hepatic encephalopathy, we used time-resolved 3D cine phase-contrast (4D-flow) magnetic resonance imaging (MRI) to assess blood flow before and after shunt embolization. Before the intervention, blood flow in the main trunk of the superior mesenteric vein was mostly hepatofugal. However, post-interventional 4D-flow MRI revealed hepatopetal superior mesenteric vein flow with significantly increased portal vein blood flow. 4D-flow MRI is an ideal adjunct to Doppler ultrasonography, allowing for objective and visual assessment of morphology and blood flow of the portal venous system, including PSSs, and is useful in determining the indications for, and outcome of, PSS embolization.     

Spontaneous intrahepatic portosystemic venous shunt in a patient with cirrhosis: diagnosis by combined color Doppler and pulsed Doppler ultrasonography

Abstract: Large spontaneous intrahepatic portosystemic venous shunts are occasionally found and their diagnosis by Doppler sonography is rarely reported. The authors describe a case of spontaneous intrahepatic porto-systemic venous shunt in liver cirrhosis diagnosed by color Doppler and characterized by an unusual pulsed Doppler spectrum: a continuous flat portal-like pattern of flow in the portal branch, and in both the shunt and the hepatic vein,     

Ultrasonography in portal hypertension

High resolution real time ultrasound is a non-invasive method of evaluating patients with suspected portal hypertension. The portosystemic collateral most frequently identified is the dilated coronary vein and its associated gastro-oesophageal varices. Other collaterals that can be seen include: gastrorenal, splenorenal, paraduodenal, periportal, pelvic and retroperitoneal varices along with a recanalized umbilical vein and ductus venosus. Using duplex doppler ultrasound, the rate and direction of portal blood flow can be ascertained. Sonography is better than barium studies in assessing whether gastro-oesophageal varices are present, however, it is not as sensitive as endoscopy, laparoscopy or portography.     

Interventional treatment for symptomatic acute-subacute portal and superior mesenteric vein thrombosis

AIM: To summarize our methods and experience with interventional treatment for symptomatic acute-subacute portal vein and superior mesenteric vein thrombosis (PV-SMV) thrombosis. METHODS: Forty-six patients (30 males, 16 females,aged 17-68 years) with symptomatic acute-subacute portal and superior mesenteric vein thrombosis were accurately diagnosed with Doppler ultrasound scans, computed tomography and magnetic resonance imaging.They were treated with interventional therapy, including direct thrombolysis (26 cases through a transjugular intrahepatic portosystemic shunt; 6 through percutaneous transhepatic portal vein cannulation) and indirect thrombolysis (10 through the femoral artery to superior mesenteric artery catheterization; 4 through the radial artery to superior mesenteric artery catheterization).RESULTS: The blood reperfusion of PV-SMV was achieved completely or partially in 34 patients 3-13 d after thrombolysis. In 11 patients there was no PV-SMV blood reperfusion but the number of collateral vessels increased significantly. Symptoms in these 45 patients were improved dramatically without severe operational complications. In 1 patient, the thrombi did not respond to the interventional treatment and resulted in intestinal necrosis, which required surgical treatment.In 3 patients with interventional treatment, thrombi re-formed 1, 3 and 4 mo after treatment. In these 3 patients, indirect PV-SMV thrombolysis was performed again and was successful.CONCLUSION: Interventional treatment, including direct or indirect PV-SMV thrombolysis, is a safe and effective method for patients with symptomatic acutesubacute PV-SMV thrombosis.     

Portal vein resection without reconstruction during Appleby operation in a patient with pancreatic body carcinoma with cavernous transformation.

The prognosis of pancreatic body carcinoma has been poor due to cancerous invasion of major vessels. Resection of the involved vessels may improve resectability and prognosis. We report a patient who had a pancreatic body carcinoma with cavernous transformation of the portal vein, in whom the portal vein was resected without reconstruction during an Appleby operation. A 67 year-old man was admitted for evaluation of back pain. Enhanced computed tomography showed no main trunk of the portal vein but a developed collateral circulation. Celiac angiography revealed encasement of the common hepatic, splenic and celiac artery. Venous angiography revealed obstruction of the portal and splenic veins with cavernous transformation surrounding these veins. Pre-operative diagnosis was carcinoma in the pancreatic body, which invaded the portal vein, the celiac and common hepatic arteries. The Appleby operation combined with resection of the portal vein without reconstruction could be performed, by preserving collateral vessels and monitoring hepatic venous oxygen saturation (ShvO2) to prevent hepatic ischemia caused by occlusion of the portal vein. The post-operative course was uneventful.     

Interventional treatment for symptomatic acute-subacute portal and superior mesenteric vein thrombosis

AIM: To summarize our methods and experience with interventional treatment for symptomatic acute-subacute portal vein and superior mesenteric vein thrombosis (PV-SMV) thrombosis. METHODS: Forty-six patients (30 males, 16 females,aged 17-68 years) with symptomatic acute-subacute portal and superior mesenteric vein thrombosis were accurately diagnosed with Doppler ultrasound scans, computed tomography and magnetic resonance imaging.They were treated with interventional therapy, including direct thrombolysis (26 cases through a transjugular intrahepatic portosystemic shunt; 6 through percutaneous transhepatic portal vein cannulation) and indirect thrombolysis (10 through the femoral artery to superior mesenteric artery catheterization; 4 through the radial artery to superior mesenteric artery catheterization).RESULTS: The blood reperfusion of PV-SMV was achieved completely or partially in 34 patients 3-13 d after thrombolysis. In 11 patients there was no PV-SMV blood reperfusion but the number of collateral vessels increased significantly. Symptoms in these 45 patients were improved dramatically without severe operational complications. In 1 patient, the thrombi did not respond to the interventional treatment and resulted in intestinal necrosis, which required surgical treatment.In 3 patients with interventional treatment, thrombi re-formed 1, 3 and 4 mo after treatment. In these 3 patients, indirect PV-SMV thrombolysis was performed again and was successful.CONCLUSION: Interventional treatment, including direct or indirect PV-SMV thrombolysis, is a safe and effective method for patients with symptomatic acutesubacute PV-SMV thrombosis.     

Embolization of the left portal vein to inferior vena cava shunts for chronic recurrent hepatic encephalopathy via the mesenteric vein

Diagnostic imaging and embolization therapy for very rare intrahepatic portal-systemic shunts with liver cirrhosis are reported. An 82-year-old woman was admitted to the hospital (Yachiyo Hospital) because of hepatic encephalopathy. Computed tomography with contrast enhancement demonstrated anomalous vessels between the portal vein and the inferior vena cava. Those shunts were suspected as the cause of her encephalopathy with hyperammonemia. Portography through McBurney's laparotomy demonstrated two portal-caval shunts; one was from the bifurcation of the portal vein and the other was from the left portal vein. They seemed to originate from the vascular system of the caudate lobe, and were obstructed with stainless coils. The patient is well with a normal serum ammonia level 40 months following the intervention.     

合并门静脉栓塞的肝移植受体术前诊断与术式研究

肝移植受体并门静脉栓塞原因通常分为门静脉血栓（PVT）和门静脉癌栓（PVTT）。术前准确诊断评价门静脉系统,对鉴别门静脉栓子性质及肝移植手术方式指导意义重大。本文对当前合并门静脉栓塞肝移植受体的术前诊断方法及伴PVT肝移植术中重建门静脉的术式进展作一简要综述。     

Diagnosis and management of ectopic varices

Abstract   Ectopic varices are dilated portosystemic venous collateral vessels that may occur anywhere in the gastrointestinal tract. Ectopic varices account for approximately 5% of all hemorrhages from varices. Ectopic varices may occur as a result of portal hypertension from any cause but are more common (particularly duodenal and biliary varices) in patients with extrahepatic portal vein thrombosis. Ectopic varices may also develop following successful endoscopic obliteration of gastroesophageal varices. With the exception of isolated gastric fundal varices, ectopic varices have relatively low risk for bleeding. Diagnosis is often made by endoscopy; however, computed tomography, magnetic resonance imaging and portal venography may be needed in some cases. Endoscopic treatment is successful in many cases and is the safest option provided bleeding is definitively controlled. Surgical options are now reserved for treatment of life-threatening bleeding or for shunt insertion in patients who are not candidates for transjugular intrahepatic portosystemic shunt (TIPS) as a result of portal vein thrombosis. Portal decompression using TIPS, in spite of the risk for encephalopathy, is the treatment of choice for bleeding from ectopic varices that cannot be successfully managed endoscopically.     

Percutaneous transhepatic catheterization of the portal venous system

During recent years, percutaneous transhepatic catheterization of the portal venous system has become the most accurate procedure for investigation of the portal system. The procedure can be performed under local analgesia, is relatively simple, and complications are rare. The success rate is high, approximately 90%, especially when the liver hilum is localized by ultrasonography prior to catheterization. The free portal pressure can be measured. Selective catheterization of all portal tributaries can be performed. The indications are: portography in patients with cirrhosis of the liver and portal hypertension for delineation of collateral vein systems including gastro-oesophageal varices; visualization of veins that may be used for portosystemic shunt operations; postoperative control of shunt patency; diagnosis of portal and hepatic vein thrombosis; localization of stenosis in the portal vein system; pre-operative evaluation of patients with tumours in the biliary tract and pancreas; obliteration of bleeding oesophageal varices; and verification and localization of endocrine pancreatic tumours making curative resection possible. Further, transhepatic catheterization of the portal system may be used in research on the development of portal hypertension, collateral veins, variceal bleeding, and for haemodynamic, metabolic and pharmacologic studies in the gastrointestinal tract.     

Pathogenesis of Portal Hypertension: Extrahepatic Mechanisms

Chronic liver diseases, including hepatic cirrhosis, chronic hepatitis, alcoholic liver disease, and hepatocellular carcinoma, are one of the commonest causes of death and liver transplantation in adults worldwide. They are accompanied by profound disturbances that are not limited to the intrahepatic circulation, but involve also the splanchnic and systemic vascular beds. These hemodynamic disturbances are responsible for the development of portal hypertension, the most frequent and severe of cirrhosis. This syndrome is characterized by a pathological increase of blood pressure in the portal vein and concomitant increases in splanchnic blood flow and portosystemic collateral vessel formation. Increased blood flow in splanchnic organs draining into the portal vein augments in turn the portal venous inflow. Such increased portal venous inflow perpetuates and exacerbates portal pressure elevation and determines the formation of ascites during chronic liver disease. In addition, portosystemic collateral vessels include the gastroesophageal varices, which are particularly prone to rupture causing massive gastroesophageal bleeding. Collateral vessels are also responsible for other major consequences of chronic liver disease, including portosystemic encephalopathy and sepsis. Extrahepatic mechanisms are clearly of major importance for disease progression and aggravation of the portal hypertensive syndrome. Accordingly, most of the therapies currently used in portal hypertension do not act inside the liver but they actually target the increased splanchnic blood flow. This paper reviews the consequences of the splanchnic circulatory abnormalities in portal hypertension and the complex signals capable of increasing vasodilatation, hyporesponsiveness to vasoconstrictors and angiogenesis in the splanchnic vascular bed and the portosystemic collateral circulation in this pathological setting.     

彩色多普勒超声诊断肝内门-体静脉分流价值探讨*

目的 探讨彩色多普勒超声检查肝内门-体静脉分流（IPSVS）的特征及诊断价值。方法 使用Philips IE33或GE LOGIQ9彩色多普勒超声诊断仪（凸阵探头,频率3.5～5.0 MHz）检查14例IPSVS患者,总结其肝脏超声图像特征及临床资料。所有患者经行多层螺旋CT检查并诊断为IPSVS。结果 在14例存在肝内门静脉分支与体循环静脉分支直接交通者中,男6例,女8例,年龄43～70岁; 1例为结肠癌并发肝内多发转移,2例为肝功能异常,8例为非肝脏疾病就诊的患者, 3例为乙型肝炎肝硬化;本组病变位于右肝12例（85.7%）,明显多于左肝2例[14.3%,P＜0.01];按Park分型,Ⅱ型5例（35.7%）,Ⅲ型9例（64.3%）;超声表现为肝内囊状或迂曲管道状无回声,与门静脉、肝静脉相通,彩色多普勒显示其内为红蓝两色交替或迂曲的血流信号,血流方向为从门静脉至肝静脉。结论 彩色多普勒超声能够敏感地发现异常血流并可测定血流方向、流速、流量,是IPSVS的首选诊断方法。