Transjugular Intrahepatic Portosystemic Shunts



Transjugular Intrahepatic Portosystemic Shunts


Mark Duncan Brooks and Changqing Li


Cirrhosis and its complications are common throughout the world. Hepatitis B and C and alcohol abuse account for about 90% of cases. Autoimmune chronic active hepatitis, primary and secondary biliary cirrhosis, hemochromatosis, Budd-Chiari syndrome, and others make up the remaining 10%. Risk of death comes from variceal bleeding, progressive liver failure, and hepatoma. Key quality-of-life issues include management of ascites and hepatic encephalopathy.


Cirrhosis is an irreversible condition, the only potential cure being liver transplantation. However, liver transplant is an expensive and complex process. There are strict selection criteria and long waiting lists for transplant. The result is a large pool of patients with portal hypertension. Transjugular intrahepatic portosystemic shunt (TIPS) is one of the treatments available to control the complications of portal hypertension.



Pathophysiology of Portal Hypertension


Venous blood from the gut, spleen, and pancreas drains via the portal venous system into the liver. It reaches the hepatic sinusoids, which drain into the hepatic veins. In cirrhosis, the liver responds to persistent damage by regenerating in nodules of hepatocytes, disrupting normal anatomy. Drainage through the sinusoids is impaired, leading to an increase in the pressure gradient between the portal vein and hepatic veins.


Two additional factors contribute to portal hypertension. Vasoconstriction in intrahepatic vessels elevates sinusoidal resistance further. Vasodilation in splanchnic vessels results in increased intestinal blood flow and a consequent increase in portal venous inflow. When portal pressure is chronically elevated, naturally existing collateral veins enlarge, becoming varices that provide alternative venous drainage from the portal venous system into systemic veins.


Esophageal varices are most common, occurring in 40% of cirrhotic patients at diagnosis and increasing by 6% per year. Gastric varices are seen in about 20% of patients and tend to occur later in the course of cirrhosis. Ectopic varices are less common. Sites include duodenum, jejunum, lienorenal, rectal, and parastomal varices. Although varices close to a mucosal surface are associated with bleeding risk, those distant from the surface are unlikely to bleed. Drainage through these veins helps keep portal pressure down.


Variceal bleeding is a major cause of death in portal hypertension. In patients with varices, the risk of a first hemorrhage is around 4% per year. Risk factors include size of varices, Child-Pugh class B or C, and hepatic vein pressure gradient (HVPG) greater than 12 mmHg. HVPG is measured using a transjugular catheter, comparing pressure when the catheter tip is wedged and free within the vein, and reflects the portal-to-systemic pressure gradient. Esophageal varices account for 70% of bleeding, and most of the remainder are gastric variceal hemorrhages. Mortality within 6 weeks of bleeding is about 30%. It is most often related to uncontrolled bleeding or early rebleeding. Other important causes of death after variceal bleeding are liver failure, multiorgan failure, and sepsis. Without preventive treatment, rebleeding occurs within 2 years in up to 65% of patients, and mortality from rebleeding is 33%.1


Ascites in patients with cirrhosis and portal hypertension is a result of multiple factors. Elevated venous pressure in the gut causes low protein fluid transudate into the peritoneal cavity. Elevated sinusoidal pressure causes high protein transudate from the liver surface. Renal effects of cirrhosis result in sodium and water retention. Reduced albumin contributes to extravascular fluid retention. Ascites causes significant impairment of quality of life. Frequent percutaneous drainage procedures may be required. Complications include spontaneous bacterial peritonitis and hepatorenal syndrome. TIPS is most effective in treatment of ascites when the HVPG is high.2




Indications


Variceal Hemorrhage


Endoscopic banding is effective in controlling acute bleeding in 80% to 90% of esophageal varices. Gastric varices are more difficult to control but may respond to endoscopic glue injection. Ectopic varices are not treatable endoscopically. Emergency TIPS is indicated when endoscopic therapy fails to control esophageal or gastric variceal bleeding and as a first-line therapy for bleeding ectopic varices. Outcomes are best when TIPS is performed early, ideally within 24 hours of presentation.3,4


TIPS is also used for prevention of rebleeding. Recurrence of bleeding after successful endoscopic control is a common problem, with high morbidity, mortality, and cost. Even with preventive medical therapy, rebleeding occurs in 25% to 33% of patients over 18 months.5 A recent randomized controlled trial identified patients with high risk of rebleed and compared the outcome of endoscopic banding plus TIPS with banding alone. The study demonstrated a marked reduction in rebleeding and improved patient survival at 1 year.4 The authors identified the timing of TIPS within 72 hours of endoscopy as a critical factor in producing an improved clinical outcome.


Gastric varices have a greater tendency to rebleed acutely after successful TIPS. Rebleeding can occur despite reducing the portal systemic pressure gradient to less than 12 mmHg. For this reason, transvenous embolization and sclerosis of varices should be performed routinely during TIPS for bleeding gastric varices.6



Ascites


Transjugular intrahepatic portosystemic shunting is effective in reducing ascites in patients with portal hypertension. In addition to symptomatic control, potential benefits are reduced risk of hepatorenal syndrome and spontaneous bacterial peritonitis. However, its role is limited by the risk of developing the complications of encephalopathy and progressive liver failure. Results of trials and meta-analyses are mixed when assessing benefits to survival and quality of life.7–11 Improvement in control of ascites can be expected in approximately two thirds of patients. New or worsened encephalopathy is seen in 32%. This can usually be controlled with medication but may require a shunt-reducing stent or shunt occlusion.12 Six-month mortality is around 36%.7 Poor outcome is more likely in those with a bilirubin level over 3 mg/dL, creatinine level over 1.5 mg/dL, and age older than 60.9 Improved ascites control is more likely in those with a higher portosystemic pressure gradient (mean 21 mmHg vs. 15 mmHg).10


Because of its potential complications and uncertain effects on life expectancy and quality, TIPS is generally considered to be indicated only in those patients with large-volume ascites that cannot be controlled with medical therapy and requires repeated large-volume paracentesis at less than monthly intervals.


Hepatic hydrothorax, in which ascitic fluid passes through defects in the diaphragm, is similar to ascites in its pathophysiology and responds to TIPS in a similar way.



Budd-Chiari Syndrome


Budd-Chiari syndrome is a rare condition resulting from occlusion of hepatic venous drainage. It can be divided into a classic form, resulting from intrahepatic venous thrombosis, and a suprahepatic form, also known as membranous occlusion of the vena cava. Our experience is confined to the classic form. Interventional procedures appear to be important in treating this condition, but its rarity and highly variable prognosis make it difficult to measure improvements in patient outcomes associated with specific treatments. Presentation is most commonly with subacute disease causing ascites and tender hepatomegaly. Less common is fulminant hepatic failure. A small percentage present with end-stage chronic liver disease. Patients with well-compensated disease, particularly where not all hepatic veins are involved, typically have a good long-term prognosis


Treatment is indicated in patients who are symptomatic or have abnormal liver function tests, suggesting ongoing damage to hepatocytes. Treatments aimed at restoring normal hepatic venous drainage include thrombolysis, angioplasty, and stenting. These may be successful at controlling symptoms in the short term, but in our experience, recurrence due to restenosis is common. If these treatments fail or are not appropriate, TIPS can be used to provide an alternative venous outflow path for the liver. TIPS provides good symptomatic control and improved liver function in both fulminant and subacute Budd-Chiari syndrome. With use of covered stents, long-term TIPS patency can be achieved, but it should be noted that this group has an increased risk of shunt stenosis and thrombosis. Regular long-term follow-up is critical because restenosis is associated with progressive liver damage.


Although no randomized studies have been performed, patients treated with TIPS have a good long-term survival compared with historical series and predicted survival based on biochemical and clinical parameters at presentation.13,14 Control of symptoms and prevention of disease progression means these patients can delay or avoid the need for liver transplantation.15



Alternatives to Transjugular Intrahepatic Portosystemic Shunt


With some patients’ liver anatomy, it may be feasible or preferred to place percutaneous portosystemic shunts directly from the inferior vena cava (IVC) to the portal vein or potentially between other portal and systemic veins with appropriate anatomy. The direct intrahepatic portosystemic shunt (DIPS) extends from the intrahepatic IVC through a short parenchymal track in the caudate lobe of the liver into the portal vein. Stented to 8 mm with a covered balloon-expandable stent, it provides a short low-resistance shunt with minimal liver trauma and low risk of restenosis.16


In patients with predicted poor outcome from TIPS, bleeding can be controlled using alternative interventional techniques, either BRTO17 or transhepatic transportal injection of sclerosant, with or without coil embolization. Although these techniques are uncommon in Western countries, they are widely practiced in some Japanese and Chinese centers to the point where they are preferred to TIPS, particularly in the treatment of gastric variceal bleeding. Published results suggest these techniques may result in improved survival with lower rates of encephalopathy and rebleeding.



Contraindications


Relative contraindications to TIPS include:



Polycystic liver disease has previously been considered a contraindication, but TIPS has been performed safely in these patients with the use of bare metal stents. It is likely to be safe with covered stents, although this remains to be tested.18 Coagulopathy, shock, and sepsis are relative contraindications, but it may still be appropriate to perform an urgent TIPS procedure while these are being corrected.


A number of anatomic features may make TIPS difficult or impossible. These include absence or thrombosis of the portal vein and distortion of venous anatomy due to liver atrophy. Modified TIPS techniques may be effective in these patients.


Other relative contraindications are predictors of poor prognosis after TIPS. The most accurate prediction of post-TIPS mortality is the Model for End-Stage Liver Disease (MELD) score. The scoring system was developed specifically for use in prediction of post-TIPS outcome.19 It provides a score based on a weighted mathematical formula including creatinine, bilirubin, and the international normalized ratio (INR):


9.6×log⁡e(Creatinine[mg/dL])+3.8×log⁡e(Bilirubin[mg/dL])+11.2×log⁡e(INR)+6.4×(etiology :0if alcoholic or cholestatic,1otherwise)


image

A 30-day mortality of 3.7% (1 in 27) is reported for patients with a MELD score of 1 to 10. Mortality increases to 60% (3 in 5) with a MELD score above 24.20


The Child-Pugh score has similar predictive effect on patient outcome after TIPS but may be slightly less accurate.21 The simplest prognostic measure is the serum bilirubin value alone. A bilirubin value over 3 mg/dL is associated with an increase in 30-day mortality after TIPS.



Equipment


Equipment required includes a TIPS set, a range of guidewires, angiographic catheters, angioplasty balloons, and stents (Table 112-1). Invasive pressure measuring equipment, appropriate patient monitoring facilities, and high-quality digital subtraction angiographic imaging are essential. Ultrasound imaging is also useful.

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Dec 23, 2015 | Posted by in INTERVENTIONAL RADIOLOGY | Comments Off on Transjugular Intrahepatic Portosystemic Shunts

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