Use of color Doppler EUS in assessing azygos blood flow for patients with portal hypertension

Diagnostic and interventional EUS in hepatology: An updated review

EUS has become an increasingly used diagnostic and therapeutic modality in the armamentarium of endoscopists. With ever-expanding indications, EUS is being used in patients with liver disease, for both diagnosis and therapy. EUS is playing an important role in providing additional important information to that provided by cross-sectional imaging modalities such as computerized tomography and magnetic resonance imaging. Domains of therapy that were largely restricted to interventional radiologists have become accessible to endosonologists. From liver biopsy and sampling of liver lesions to ablative therapy for liver lesions and vascular interventions for varices, there is increased use of EUS in patients with liver disease. In this review, we discuss the various diagnostic and therapeutic applications of EUS in patients with various liver diseases.

Application of ultrasound for the diagnosis of cirrhosis/portal hypertension

With advances in technologic approaches in patients with cirrhosis, including the improvement of management, a simple, one-step approach for advanced fibrotic state of the liver is clinically useful. Although refining the diagnosis of cirrhosis to reflect disease heterogeneity is essential, current diagnostic tests have not kept pace with the progression of this new paradigm. There are unmet needs in primary care centers with respect to patients with cirrhosis. Liver biopsy and measurement of hepatic venous pressure gradient in patients with cirrhosis are the gold standards for the estimation of hepatic fibrosis, and they have diagnostic and prognostic value. However, both approaches are invasive and cannot be used repeatedly in clinical practice. Ultrasonography (US) is safe, easy to perform, inexpensive, and yields numerical and accurate results. Conventionally, the size of the liver and spleen, bluntness of the liver edge, nodularity of the liver surface, and coarseness of the liver parenchyma have been known as useful parameters for hepatic fibrosis or portal hypertension (PHT) in chronic liver disease. Additionally, some functional US indices including Doppler and CEUS-based examination have been suggested as promising markers for diagnosing cirrhosis and PHT. Identification of the reproducibility and long-term prognostic value through further investigations can demonstrate the clinical usefulness of functional US indices, which are characterized as quantitative parameters for hepatic fibrosis and PHT.

The role of EUS in diagnosis and treatment of liver disorders

Background and aim  Transabdominal ultrasound (US), computed tomographic scanning (CT) and magnetic resonance imaging (MRI) are established diagnostic tools for liver diseases. Percutaneous transhepatic cholangiography is used to perform hepatic interventional procedures including biopsy, biliary drainage procedures, and radiofrequency ablation. Despite their widespread use, these techniques have limitations. Endoscopic ultrasound (EUS), a tool that has proven useful for evaluating the mediastinum, esophagus, stomach, pancreas, and biliary tract, has an expanding role in the field of hepatology complementing the traditional investigational modalities. This review aimed to assess the current scientific evidence regarding diagnostic and therapeutic applications of EUS for hepatic diseases.

Utility of endoscopic ultrasound in the diagnosis and management of esophagogastric varices

Endoscopic ultrasound (EUS) has significantly improved our understanding of the complex vascular structural changes in patients with portal hypertension. At present, EUS is a useful diagnostic tool for the evaluation of esophagogastric varices (EGVs) and guidance of endoscopic therapy. Several studies have employed this new technique for the diagnosis and management of esophageal and gastric varices, respectively. In the present review, we have summarized the current status of EUS for the diagnosis and management of EGVs and clarified the clinical feasibility of this procedure. New indications for EUS can be developed in the future after adequate validation.

Three months of simvastatin therapy vs. placebo for severe portal hypertension in cirrhosis: A randomized controlled trial

BACKGROUND

Pleiotropic effects of statins decrease intrahepatic resistance and portal hypertension.

AIM

We evaluated the effects of simvastatin on hepatic venous pressure gradient (HVPG) and azygos vein blood flow in cirrhotic patients.

METHODS

A 3-month prospective, randomized, triple-blind trial with simvastatin (40 mg/day) vs. placebo was conducted in patients with cirrhotic portal hypertension. HVPG and azygos blood flow, measured by colour Doppler endoscopic ultrasound, were assessed before and after treatment. The primary endpoint was a decrease in the HVPG of at least 20% from baseline or to ≤12 mmHg after the treatment.

RESULTS

34 patients were prospectively enrolled, and 24 completed the protocol. In the simvastatin group 6/11 patients (55%) presented a clinically relevant decrease in the HVPG; no decrease was observed in the placebo group (p=0.036). Patients with medium/large oesophageal varices and previous variceal bleeding had a higher response rate to simvastatin. HVPG and azygos blood flow values were not correlated. No significant adverse events occurred.

CONCLUSION

Simvastatin lowers portal pressure and may even improve liver function. The haemodynamic effect appears to be more evident in patients with severe portal hypertension.

Haemodynamic evaluation by Doppler ultrasonography in patients with portal hypertension: a review

Doppler ultrasonography (US) has an advantage of being non-invasive; therefore, several attempts have been made to investigate the haemodynamic alterations in cirrhosis and the response to medical treatment of portal hypertension. Doppler indices, which have been commonly used for the evaluation of portal hypertension, include the measurement of portal and splenic venous blood velocity and flows, and the resistive and pulsatility index at hepatic, splenic, renal, superior mesenteric artery. Although many positive evidences have been suggested, its clinical usefulness in portal hypertension remains unsettled because of being plagued by lack of reproducibility and accuracy characterized by intra- and interobserver variation. However, recently, Doppler's usefulness in assessment of severity of portal hypertension in terms of reproducibility, technical ease and accuracy and response to drugs that reduce the portal pressure has been proposed. In addition, because most of the patients with cirrhosis and portal hypertension have intrahepatic shunts, they show a decrease in intrahepatic circulatory time (IHCT). Doppler US using microbubble contrast agents allows measurement of IHCT. Therefore, application of contrast-enhanced Doppler US can be prospective for the assessment of the severity of portal hypertension. Several reports have demonstrated that colour Doppler endoscopic US enable haemodynamic study to assess the portal hypertension and has a role of guidance to measure the imaging-based variceal pressure. We have reviewed briefly the clinical usefulness of Doppler US in assessing the severity of portal hypertension and its response to treatment.

Validation of endoscopic ultrasound measured flow rate in the azygos vein using a flow phantom

Increase in flow rate within the azygos vein may be used as an indicator of the degree of liver cirrhosis. The aim of this study was to evaluate the error in measurement of flow rate using a commercial endoscopic ultrasound system, using a flow phantom that mimicked azygos vein depth, diameter and flow rate. Diameter was underestimated in all cases, with an average underestimation of 0.09 cm. Maximum velocity was overestimated, by 4 ± 4% at 50°, 11 ± 3% at 60° and 23 ± 7% at 70°. The increase in error with beam-vessel angle is consistent with the error as arising from geometric spectral broadening. Flow was underestimated by amounts up to 33%, and it is noted that the overestimation caused by geometric spectral broadening is in part compensated by underestimation of diameter. It was concluded that measurement of flow rate using a commercially available endoscopic ultrasound system is dependent on the beam-vessel angle, with errors up to 33% for typical vessel depths, diameter and beam-vessel angle.

Endoscopic ultrasonography for the evaluation of portal hypertension

Since the 1980s, endoscopic ultrasonography (EUS) has been useful in the evaluation of portal hypertension, either for the diagnostic aspects or for the evaluation of therapy and risk of bleeding. More recently, it has been described as a method for guiding interventions such as variceal injection, portal vein catheterization, or even for creating an intrahepatic portosystemic shunt in the animal laboratory. The new generation of radial electronic echoendoscopes is equipped with color Doppler capability, allowing for measurement of any hemodynamic parameter of the portal circulation. This article summarizes the current knowledge on the role of EUS for the evaluation of portal hypertension.

Endoscopic ultrasonography and portal hypertension: where are we in 2009?

Endoscopic ultrasonography is currently a sensitive diagnostic and therapeutic tool with established indications, but its role in the management of portal hypertension is not well defined. This article briefly reviews indications, technologic improvements, diagnostic and interventional applications of endoscopic ultrasonography in portal hypertension.

Systematic review: endoscopic and imaging-based techniques in the assessment of portal haemodynamics and the risk of variceal bleeding

BACKGROUND

Invasive measurement of the hepatic venous pressure gradient (HVPG) is regarded as the gold standard for risk stratification and the evaluation of pharmaceutical agents in patients with portal hypertension.

AIM

To review the techniques for endoscopic and imaging-based assessment of portal haemodynamics, with particular emphasis on trials where the results were compared with HVPG or direct portal pressure measurement.

METHODS

Systematic search of the MEDLINE electronic database with keywords: portal hypertension, variceal bleeding, variceal pressure, endoscopic ultrasound, Doppler ultrasonography, magnetic resonance angiography, CT angiography, hepatic venous pressure gradient.

RESULTS

Computed tomography angiography and endoscopic ultrasound (EUS) have been both employed for the diagnosis of complications of portal hypertension and for the evaluation of the efficacy of endoscopic therapy. Colour Doppler ultrasonography and magnetic resonance angiography has given discrepant results. Endoscopic variceal pressure measurements either alone or combined with simultaneous EUS, correlate well with HVPG and risk of variceal bleeding and have a low interobserver variability.

CONCLUSIONS

Endoscopic and imaging-based measurements of portal haemodynamics provide an alternate means for the assessment of complications of portal hypertension. Further studies are required to validate their use in risk stratification and the evaluation of drug therapies in patients with portal hypertension.

[Non-invasive diagnosis of portal hypertension in cirrhosis. Application to the primary prevention of varices]

One of the major complications of cirrhosis is the occurrence of portal hypertension and esophageal varices. At present, universal endoscopic screening of esophageal varices is recommended in association to primary prophylaxis in patients at high risk of variceal bleeding. But this screening is invasive and could be not cost-effective. Besides, pre-primary phrophylaxis is not effective and hampared by side effects. So, non invasive diagnosis of portal hypertension might be useful. This one could depend on non invasive measurement of hepatic venous pressure gradient, but its application to screening is not well-documented and its use in treatment monitoring is debated. A second way could be non invasive diagnosis of large esophageal varices because of prognostic and economic issues. Indirect echographic markers of portal hypertension and esophageal varices (ascites, portal vein diameter > or = 13 mm, spleen length, maximal and mean velocimetry of portal vein flow, respectively < 20 cm/s and < 12 cm/s) could be useful. Among this parameters, spleen length is an independent predictive marker of esophageal varices. Besides, several direct or indirect blood markers of fibrosis have been tested. Platelet count is repeatedly a predictive marker of esophageal varices in multivariate analysis. The other predictive factors of esophageal varices could be: prothrombin time, splenomegaly, spider naevi, Child-Pugh class, bilirubinemia, platelet count/spleen diameter ratio and Fibrotest, but these data require validation. In summary, in regard to actual results, non invasive diagnosis of portal hypertension might be useful in esophageal varices screening, but the substitutes to endoscopy have limited place actually in clinical practice, and exclusive non invasive diagnosis of portal hypertension is not applicable; the only test that seems to be useful in clinical practice is conventional endoscopy awaiting the results of videocapsule.

Endoscopic ultrasonography in the diagnosis and management of portal hypertension. Where are we next?

Endoscopic ultrasonography has recently emerged as an accurate, non-invasive and reproducible alternative means of providing data for patients with portal hypertension. It is well established that endoscopic ultrasonography is more sensitive than endoscopy in the diagnosis of gastric varices. Dilated venous abnormalities outside the gastrooesophageal lumen, which cannot be diagnosed by endoscopy, are readily visible with endoscopic ultrasonography or miniature probes. Endoscopic ultrasonography is also useful to predict the risk of variceal recurrence and thus the risk of rebleeding after endotherapy which cannot be reliably predicted using endoscopy alone. The introduction of echo endoscopes equipped with Doppler facilities has allowed the sonographic visualisation of the vessels and the evaluation of vascular blood flow along with possible morphologic and haemodynamic changes after endoscopic or pharmacological therapy. However, despite its theoretical advantages, relative evidence suggests that in the clinical setting of portal hypertension, endoscopic ultrasonography remains an investigational tool with limited clinical applications.

EUS-guided portal vein catheterization and pressure measurement in an animal model: a pilot study of feasibility

BACKGROUND

The extrahepatic portal vein is inaccessible to direct catheterization.

METHODS

Because EUS can readily image the portal vein, the feasibility of EUS-guided portal vein catheterization by using a 22-gauge needle was studied in 7 normal pigs and 14 pigs in which portal hypertension was induced (7/14 anticoagulated).

RESULTS

Catheterization was not possible by EUS or transhepatic methods in, respectively, 3 and 5 animals. One anticoagulated animal had a small amount of periduodenal bleeding as a result of EUS catheterization. The mean normal portal vein pressure (1 standard deviation) as determined by EUS and transhepatic methods was, respectively, 20.3 (4) mm Hg and 20.4 (2) mm Hg. Injection of polyvinyl alcohol particles increased the portal vein pressure by 10.2 (11.59) mm Hg. There was a close correlation under all conditions between the mean portal vein pressures obtained by EUS and transhepatic catheterization (r=0.91).

CONCLUSIONS

EUS-guided portal vein catheterization appears to be feasible in an animal model and provides accurate pressure measurements.

Pharmacological rationale for the use of somatostatin and analogues in portal hypertension

Somatostatin and its analogue octreotide have been used for two decades to treat oesophageal variceal haemorrhage. The drug was introduced because of its capacity to decrease portal venous pressure without major side effects. In clinical trials assessing the efficacy of somatostatin and long-acting analogues in arresting variceal haemorrhage, conflicting results have been obtained. Furthermore, in haemodynamic studies evaluating the effects of somatostatin and analogues in patients with cirrhosis, divergent effects were observed. The main reason for these differences is probably related to different affinities of the drugs for different somatostatin receptor subtypes. The effects of somatostatin and analogues are mediated via five different G-protein coupled receptors (somatostatin receptor subtypes 1-5), which regulate the activity of ion channels (Ca2+, K+, Na+ and Cl-) and enzymes (adenyl cyclase, phospholipase C, phospholipase A2, phosphoinositide 3-kinase and guanylate cyclase) responsible for the synthesis or degradation of intracellular second messengers including cyclic AMP, inositol 1,4,5-trisphosphate, diacylglycerol and cyclic GMP. Despite universal use of somatostatin, the cellular and biochemical mechanisms of its effects in portal hypertension are relatively poorly studied and remain incompletely understood. In this review, we summarize relevant signal transduction of somatostatin and analogues, the haemodynamic effects of the drugs and the possible mechanisms by which these effects are mediated.

Laboratory assessment of hepatic hemodynamics

Although the study of hepatic circulation is complicated by the dual blood supply and complex anatomy of the liver, many distinct methods are available to facilitate its study. Before embarking on an investigation of hepatic hemodynamics, the investigator must be familiar with the available methods and their applications. All methods have their own attributes and limitations. No one method is superior to the others, but, depending on the aspect of hepatic hemodynamics to be investigated, a particular methodology may yield distinct advantages.

Validation of color Doppler EUS for azygos blood flow measurement in patients with cirrhosis: application to the acute hemodynamic effects of somatostatin, octreotide, or placebo

BACKGROUND

Color Doppler EUS (CD-EUS) allows minimally invasive measurement of azygos blood flow (AzBF) in portal hypertension, but further validation of the method is needed. Because a limited number of patients has been studied, the acute hemodynamic effects of somatostatin and octreotide on AzBF and gastric mucosal perfusion are poorly defined in portal hypertension.

METHODS

A double-blind hemodynamic study was designed to assess rapid changes in AzBF over a 60-minute period after intravenous administration of somatostatin, octreotide, and placebo in 30 stable patients with biopsy-proven cirrhosis. AzBF was measured by using both CD-EUS and the invasive thermal dilution technique in the first 10 patients (phase 1). Then, with CD-EUS alone, the hemodynamic study was extended to a further 20 patients (phase 2). In addition, gastric mucosal perfusion changes were assessed by using laser Doppler flowmetry at endoscopy.

RESULTS

In phase 1, the 2 methods for AzBF measurement showed significant correlations both for baseline values (r = 0.685) and for AzBF changes over 60 minutes after drug administration (r = 0.733). In phase 2, a reduction was observed in AzBF 10 minutes after octreotide or somatostatin administration (-47% and -23%, p < 0.0001 vs. placebo, p = 0.058 vs. placebo, respectively). After 60 minutes of somatostatin infusion, AzBF increased 27% over placebo values (p < 0.04). Gastric mucosal perfusion was transiently reduced 5 minutes after octreotide or somatostatin (-21% and -32%, respectively, p < 0.02 vs. placebo).

CONCLUSIONS

This is the first study to validate CD-EUS AzBF measurement with reference to the invasive thermodilution technique in cirrhosis. It confirmed the transient effects of somatostatin and octreotide on both AzBF and gastric mucosal perfusion. In addition, a significant rebound phenomenon after 60 minutes of continuous intravenous somatostatin infusion was observed.

Portal hypertension

Many advances in the management of portal hypertension and variceal hemorrhage have occurred during the last 10 years. Effective therapy for primary prevention of variceal hemorrhage is now available in the form of nonselective beta-blockers. Active bleeding should be managed with terlipressin, somatostatin or its analogues, and endoscopic therapy; TIPS and surgery are reserved as salvage therapy for patients who fail endoscopic treatment. Survivors of a variceal hemorrhage should be evaluated for liver transplantation. Specific treatment may be provided with EVL while these patients await transplantation. Patients who fail endoscopic treatment may be treated by TIPS or surgery.