Chapter 27: Pediatric Portal Interventions While portal interventions on adults have become commonplace, as most interventionalists are comfortable with the variety of different approaches, portal interventions in children are perhaps more daunting due to their relative infrequency and operator trepidation around performing complex interventions on children. While it is easy to say kids are just small adults, and one can tailor the procedure to a small adult, this is only partially true given certain considerations in children (including preoperative, intraoperative, and postoperative management) that one should be aware of when treating children. Furthermore, certain conditions may present in the pediatric population that may be best managed according to a different algorithm than an adult counterpart. Additionally, these complex portal interventions likely get triaged to larger academic institutions with pediatric liver transplant programs and dedicated children’s hospitals; therefore, these interventions may not be a routine practice. With children, interventional radiologists can provide a great service by offering a minimally invasive approach in managing a life-threatening disease process. In lieu of creating a surgical splenorenal or mesocaval shunt, creating a transjugular portosystemic shunt (TIPS) can be life-saving in a child with variceal bleeding. Congenital abnormalities, such as direct portosystemic shunts and Abernethy malformations, may be discovered early in the pediatric population and be managed with minimally invasive interventional techniques. Children commonly present in ways similar to adults including with variceal bleeding, ascites, or hepatic hydrothorax. However, the etiology of portal hypertension in children is certainly different than in adults. In adults, portal hypertension is often the result of alcohol consumption or underlying liver cirrhosis secondary to hepatitis or non-alcoholic steatohepatosis (NASH); in children, the causes may be congenital or acquired. Post–chemotherapy-related liver disease after leukemia treatment is one situation where a child may present with portal hypertension. Long-term jejunal tube feeding in the setting of chronic liver disease may result in stomal variceal formation, which may be prone to bleeding. Children with biliary atresia may undergo liver transplantation and be susceptible to the complications that go along with it, including hepatic artery occlusion or portal vein anastomotic narrowing. Another etiology in senestral (left-sided) portal hypertension due to splenic thrombosis is dehydration in infants and small children. These are all complications that can be managed from a minimally invasive interventional approach, and, in children, this is generally preferable compared to larger open-surgical operations. The remainder of this chapter is divided along technical (procedural) lines. Due to the longer life expectancy of children relative to their adult counterparts with portal hypertension, TIPS creation may be a bridge to liver transplantation in the setting of portal hypertension. Although the techniques for placement of a TIPS are similar among adults and children, factors to consider include the smaller size of the liver and consequently the smaller size of the hepatic veins and portal branches. Shunts may also need to be tailored and may eventually be modified as the child grows.1 Depending on the degree of portal hypertension and the specific circumstances, direct transhepatic portal access or transjugular transhepatic portal sclerotherapy without placement of a TIPS may be options to consider to avoid potential complications associated with creation of a TIPS, such as hepatic encephalopathy, liver failure and right heart failure.1,2 Children are much more susceptible to these potential risks if appropriate pre-procedural screening or planning is not undertaken. In the setting of a variceal hemorrhage, often the first line of management may be endoscopic with banding, vasoconstricting medication injection, or glue directly into the varices. In the setting of a life-threatening hemorrhage, a Sengstaken-Blakemore occlusion balloon may also be placed. Medical management may include beta-blockers, vasopressin, pressor support, and/or octreotide with supportive therapy with blood and fluid resuscitation. Creation of a TIPS in a child is similar to that in an adult. Internal jugular vein access is obtained and, depending on the size of the child, ideally a 10-F, 40-cm sheath is placed. A catheter such as an MPA or C2 Cobra catheter (with tip cut off) is utilized to select a hepatic vein branch (right or middle). Venography is performed with contrast and then with CO2 while the catheter is wedged, in order to obtain a map of the portal venous system. A Rosch Uchida set or a Colapinto needle is used to make a puncture into a portal venous branch from the hepatic vein. Once needle positioning is confirmed with contrast, a wire is placed into the portal venous system. A catheter is then passed into the portal venous system and a stiff wire such as an Amplatz wire is placed. Pressures are measured, the tract is measured, the balloon dilated, and a stent is placed. Eight- to 10-mm diameter Viatorr stentgrafts (Gore & Associates, Flagstaff, AZ) can be placed to establish TIPS in larger children and adolescents as shown in Variceal sclerotherapy using sotradecol, alcohol, and/or coils should also be performed. Patients should be admitted postoperatively to assess for complications, which, similar to adults, include bleeding, hepatic encephalopathy and liver failure. TIPS in pediatric transplant recipients can be particularly challenging because the recipients commonly have split grafts. Left hepatic lobe split grafts are particularly challenging because of the size of the liver and vessels as well as the unfamiliar orientation of the vessels because most operators are used to right-sided TIPS (from right or middle hepatic to right portal trajectories). Moreover, split left lobe grafts (especially segment 2/3 grafts) grow, rotate, and may have rotated vessels conventionally oriented.3–5 Portal vein thrombosis (PVT) occurs at a rate of approximately 12% in pediatric patients after liver transplantation. Patients with late PVT, defined as detection 30 or more days after transplant, often present with variceal bleeding, which can cause significant morbidity. Pediatric liver transplant patients pose unique challenges to successful portal vein recanalization due to altered anatomy, postoperative fibrosis, and smaller caliber vessels. However, essentially the same techniques that are utilized in adults can be similarly employed in children to recanalize an occluded portal vein. In children, generally portal vein occlusion/stenosis is most likely in the setting of a liver transplant. Young children most commonly receive liver transplants in the setting of biliary atresia. Splenic vein thrombosis, which may propagate to PVT, may be due to infection and/or dehydration in small children, especially in warm/tropical environments. Recanalization of the portal vein can be performed from either a transhepatic or trans-splenic approach ( Depending on the degree, length, and chronicity of occlusion, recanalization may be difficult and may require multiple approaches and potentially sharp recanalization. Follow-up ultrasound and/or MRI of these patients is advisable both initially for diagnosis as well as in follow-up to ensure no restenosis. It is easier to remedy any problems if they are discovered early. A pure subacute/acute stenosis may potentially respond to angioplasty alone; however, more chronic long-standing occlusions that have progressed over time likely require support with a stent. The tract, whether trans-splenic or transhepatic, should be embolized with either coils, gelfoam pledgets, or glue (N-butyl cyanoacrylate). Particularly with the trans-splenic (especially in the setting of splenomegaly) approach, there is a definite concern for post-procedural bleeding, and therefore the patient should be admitted to the hospital postoperatively to assess for signs of bleeding. As these pediatric cases are commonly performed with general anesthesia, one has to ensure that when the patient awakens from anesthesia there is not a sudden increase in intra-abdominal pressure, which results in bleeding. It may be wise to hold pressure at the puncture site while the patient is waking up from anesthesia, particularly with the trans-splenic approach in children. A follow-up ultrasound should also be performed the subsequent day to ensure that no acute complications develop from the access and to ensure stent patency. Children with portal hypertension, similar to their adult counterparts, can develop spontaneous splenorenal shunts, esophageal and gastric varices, and enteric varices. Enteric varices are an uncommon manifestation of portal hypertension and occur in about 5% of patients with portal hypertension. Treatment may include surgery, TIPS, enteroscopic sclerotherapy, percutaneous embolization, and occasionally the stenting of a stenosed portal vein. Treatment planning should begin with MRI/MRV of the portal venous system to minimize radiation dose in the pediatric population. MRI/MRV provides for treatment planning prior to performing a procedure. Approaches to treating varices are similar to that in adults, though—if possible in smaller children—avoiding a TIPS at least initially is preferable until they reach full-grown size. Transhepatic access to the portal venous system is preferred in children with a balloon antegrade transvenous obliteration approach (BATO) with coils and sodium tetradecyl sulfate (STS) ( Gastrorenal shunts (a prerequisite for conventional balloon-occluded retrograde transvenous obliteration–BRTO) in the setting of gastroesophageal varices or isolated gastric varices have recently been described in children.2,6 Prior to this recent report, gastrorenal shunts (GRS), and thus conventional BRTO, were only described in adults.2 According to the report, conventional BRTO for children with bleeding gastric varices is technically feasible along similar lines with BRTO in adults albeit with smaller balloon sizes and less foam sclerosant volumes.2 Partial splenic embolization has also been described as an adjunct to variceal sclerosis in the setting of partial or complete portal vein thrombosis and/or complete splenic vein thrombosis (see below).2 Partial splenic embolization is usually performed for either (1) symptomatic portal hypertension or (2) hypersplenism (not synonymous with symptomatic portal hypertension) for the management of thrombocytopenia or pancytopenia. In the treatment of symptomatic portal hypertension, the authors resort to partial splenic embolization either to augment other management approaches (BRTO, for example) or as the only/least-invasive option for managing portal hypertension (managing gastroesophageal varices without a shunt, for example). Recently recanalized portal vein and/or splenic vein is a relative contraindication to splenic embolization because it reduces the inflow to the splenic/portal vein and thus may predispose to premature rethrombosis after the recanalization. Complications from splenic embolization are post-embolization syndrome, liquefactive infarction with superadded infection (abscess formation), and severe flank pain. Unlike in adults, the flank pain after splenic embolization in children can be a source of considerable morbidity requiring hospital admission for hydration and pain management. In order to reduce the risk of liquefactive infarction and make the post-procedural pain manageable, the authors prefer to do multiple2 embolization sessions with 25% to 35% of the splenic parenchymal infarcted per session. The interval between sessions would be at least 6 to 8 weeks, and the schedule of the sessions can be tailored to the child’s schedule (school and summer activity schedule). If large areas of the spleen are embolized (intentionally or inadvertently), careful surveillance of the platelet count may be warranted to make sure the platelet count does not become excessively high. Excessively high platelet counts may lead to thrombogenic states and thrombose the splenic and portal veins, particularly when coupled with the reduced inflow effect of embolizing a large portion of the spleen.
Introduction
Transjugular Intrahepatic Portosystemic Shunts (TIPS)
Technique
Fig. 27.1. However, in smaller prepubertal children, balloon-expandable stents are preferred to provide adequate—but not excessive—portal decompression but at the same time allow subsequent expansion of the shunt to 8 to 10 mm as the child grows. As a general rule, 8- to 10-mm TIPS can take a child into adolescence and adulthood.
Portal Vein Recanalization
Fig. 27.2). The transsplenic approach may be preferable in some situations due to the straight-line approach provided the splenic vein is patent. A transhepatic portal vein approach using ultrasound or fluoroscopic guidance can also be performed. Generally stenting should be performed with balloon expandable covered stents such as the iCast stent (Atrium Medical) (
Fig. 27.2). This allows for the stent to be dilated as needed in the future as the child grows. Again, similar to TIPS, 8- to 10-mm portal vein stents can take a child into adolescence/adulthood.
Variceal Sclerotherapy
Fig. 27.3). Depending how superficial the varices are, 1% STS may be preferred over 3% STS. Following sclerotherapy of the varices, embolization of the transhepatic portal tract can be performed with coil/gelfoam pledgets or glue (N-butyl cyanoacrylate). Direct percutaneous access into the varices using ultrasound guidance with direct sclerotherapy could also be performed in this setting.
Splenic Embolization
Thoracic Key
Fastest Thoracic Insight Engine
