Bailliere's clinical gastroenterology最新文献

Recent advances in the pharmacology of portal hypertension are reviewed, against the background of existing knowledge and current clinical research. The most recent trials are analysed, and conclusions made about the use of drugs in acute variceal haemorrhage, as well as directions for further clinical trials and research.

Patients with suspected portal hypertension must first be evaluated by physical examination, upper digestive endoscopy and ultrasonography with Doppler. Moreover, the evaluation of patients with portal hypertension depends on the cause of portal hypertension, the presence of complications and the specific treatment considered. Haemodynamic assessment with measurement of the hepatic venous pressure gradient is useful in confirming the origin of portal hypertension. This technique is the ‘gold-standard’ for evaluating haemodynamic treatments. Splanchnic and systemic circulation must also be measured. Quantitative evaluation of the splanchnic territory by Doppler sonography and other non-invasive investigations, may be performed. Further clinical studies are, however, needed to determine their interest in portal hypertension.

The role of surgery in portal hypertension remains a topic of debate. For the past 100 years, various surgical procedures have been used to treat variceal bleeding, refractory ascites, and end-stage liver disease. The past decade has seen significant advances in pharmacotherapy, endoscopy, interventional radiology, and surgery for the management of patients with portal hypertension. Liver transplantation has come of age in the 1990s and is now an accepted therapy for patients with end-stage liver disease. The wide array of management options can complicate the decision making process and defines the need to evaluate these patients fully. Factors such as the aetiology and extent of liver disease, response to prior medical, endoscopic, and other interventional treatments, and possibility of future liver transplantation must be considered. This manuscript will review the history of surgical treatments of portal hypertension, describe the surgical procedures with their advantages and disadvantages, and evaluate their role in the elective and emergent settings.

Transjugular intrahepatic portosystemic shunt (TIPS) is a procedure recently introduced for the management of complications of portal hypertension. TIPS can be placed in the liver with relative ease by a skilled radiologist with a low risk of mortality. The major complications following the procedure are infection, especially in patients undergoing emergency TIPS, intra-abdominal haemorrhage from capsular punctures, and long-term problems related to encephalopathy and stenosis of the shunt. Encephalopathy is more of a problem in older patients with wide diameter shunts. Stenosis of the shunt is related to pseudo-intimal hyperplasia, probably related to transection of bile ductules during placement of the shunt. In view of the high rate of encephalopathy and stenosis following the shunt, a careful follow-up of all patients, including ultrasonographic and angiographic examination of the shunt, is mandatory. TIPS is used predominantly for the control of acute variceal haemorrhage, prevention of recurrent variceal bleeding, and refractory ascites when conventional treatment has failed. However, the role of TIPS in the management of complications of portal hypertension still awaits the outcome of clinical trials.

In the past few years, there have been important advances in the field of pathogenesis and management of ascites and hepatorenal syndrome in cirrhosis. A new pathogenic theory of ascites and renal dysfunction in cirrhosis has been presented and previously ill-defined conditions, such as refractory ascites and hepatorenal syndrome, have been defined precisely. The link between the diseased liver and the disturbances in renal function and vasoactive systems is not completely known, but a large body of evidence indicates that it consists of a circulatory dysfunction that affects mainly the arterial circulation and is characterized by an inability to maintain an effective arterial blood volume within normal limits. The research on the mechanisms of this circulatory dysfunction will give valuable information in the design of more pathophysiologically oriented therapeutic approaches to the management of ascites.

Promoting the development of oesophageal varices and ascites, portal hypertension dominates the clinical course of cirrhosis. Varices appear in patients with portal pressure gradient above 10 mmHg and enlarge in 10–20% within 1–2 years of their detection. Bleeding occurs in patients with portal pressure gradient above 12 mmHg when the wall tension causes the rupture of varices, with an incidence of about 10% per year. Indicators of bleeding risk are portal pressure gradient, variceal pressure, large varices and liver dysfunction. Mortality per bleeding episode is 30–50%. Among survivors 60% will rebleed and 30% will die in the following year. The risk of rebleeding decreases in patients with spontaneous or treatment induced reduction of portal pressure gradinent or variceal pressure. Ascites develops in almost all patients along the course of the disease. Median survival after its appearance is less than 2 years. Less than 5% of cirrhotic patients die without ascites or without a previous bleeding. Thus portal hypertension is a major determinant of survival in cirrhosis.

The introduction of pharmacological therapy has been one of the major advances in the treatment of the complications of portal hypertension. Many drugs have been shown to reduce portal hypertension in patients with cirrhosis. However, the most widely used drugs and the only ones for which there is sufficient evidence, are the beta-blockers. These drugs have been, up to now, the only accepted prophylactic therapy for oesophageal variceal bleeding and are also an alternative treatment to sclerotherapy or surgery to prevent variceal rebleeding. A reduction in portal pressure gradient by beta-blockers below 12 mmHg or by more than 20% of baseline values is associated with almost a total protection from oesophageal bleeding. Such a marked response in portal pressure is only achieved in some patients receiving propranolol. New pharmacological approaches with a greater portal pressure reducing effect may improve the beneficial effect of drugs in preventing variceal bleeding. The more promising approach is the combined administration of beta-blockers and isosorbide-5-mononitrate, which has been shown to potentiate the reduction in portal pressure and to be highly effective in initial randomized clinical trials.

The current chapter deals with the concept, clinical manifestations and diagnostic tools of the hepatopulmonary syndrome (HPS) and highlights its most salient pathophysiological, mechanistic and therapeutic aspects. Defined as a clinical triad, including a chronic liver disorder, pulmonary gas exchange abnormalities and generalized pulmonary vascular dilatations, in the absence of intrinsic cardiopulmonary disease, this entity is currently growing in interest with both clinicians and surgeons. The combination of arterial hypoxaemia, high cardiac output with normal or low pulmonary artery pressure, and finger clubbing in a patient with advanced liver disease should strongly suggest the diagnosis of HPS. Its potential high prevalence together with failure of numerous therapeutic approaches depicts a life-threatening unique clinical condition that may dramatically benefit with an elective indication of liver transplantation (LT). A better orchestration of the concepts of the pathophysiology of this lung-liver interplay may foster our knowledge and improve the clinical management and indications of LT.

Portal hypertension is a common clinical syndrome associated with chronic liver diseases and is characterized by a pathological increase in portal pressure. Increase in portal pressure is because of an increase in vascular resistance and an elevated portal blood flow. The site of increased intrahepatic resistance is variable and is dependent on the disease process. The site of obstruction may be: pre-hepatic, hepatic, and/or post-hepatic. In addition, part of the increased intrahepatic resistance is because of increased vascular tone. Another important factor contributing to increased portal pressure is elevated blood flow. Peripheral vasodilatation initiates the classical profile of decreased systemic resistance, expanded plasma volume, elevated splanchnic blood flow and elevated cardiac index. The elevated portal pressure leads to formation of portosystemic collaterals and oesophageal varices. Pharmacotherapy for portal hypertension is aimed at reducing both intrahepatic vascular tone and elevated splanchnic blood flow.

Endoscopic treatments for bleeding gastro-oesophageal varices include injection sclerotherapy, variceal obturation with tissue adhesives and variceal rubber band ligation. Today, endoscopic treatments are not recommended for the primary prophylaxis of variceal bleeding. Acute injection sclerotherapy remains a quick and simple technique for the control of active bleeding from oesophageal varices. Its efficacy may be improved by the early administration of vasoactive drugs. Banding ligation is the optimal endoscopic treatment for the prevention of rebleeding from oesophageal varices. The use of tissue adhesives and thrombin as injectates to treat bleeding fundal gastric varices and oesophageal varices not responding to vasoactive drugs or sclerotherapy is promising but needs further assessment by means of randomized controlled trials.