UNASSIGNED: Down syndrome is due to trisomy 21 and is characterized by intellectual disability, dysmorphic facial features, congenital malformations, and gastrointestinal abnormalities. There is an increased appreciation of congenital portosystemic shunts in Down syndrome patients. Congenital portosystemic shunts have been associated with many defects in body systems, including cardiac, metabolic, and neurological.
UNASSIGNED: Herein, we describe a portosystemic shunt in a Down syndrome patient that resulted in hyperammonemia with altered mental status and choreiform movements. Computed tomography angiography of the abdomen and pelvis identified a connection between the right portal vein and inferior vena cava. An 18 mm Amplatzer PFO closure device was placed within the congenital shunt, significantly improving symptoms. The patient has no sequelae from the related shunt or the device at the 2-year follow-up. We extensively reviewed the literature and identified cases of portosystemic shunts in Down syndrome patients. Shunts can either be extrahepatic or intrahepatic and are classified by vasculature connections.
UNASSIGNED: From our literature review and case presentation, we identify other conditions in patients, including cardiac and gastrointestinal defects. We then review the available treatment options, whether observation or surgical, depending on the patient\'s clinical picture.

BACKGROUND: Abernethy syndrome is a congenital vascular anomaly in which the portal blood completely or partially bypasses the liver through a congenital portosystemic shunt. Although the number of recognized and reported cases is gradually increasing, Abernethy syndrome is still a rare disease entity, with an estimated prevalence between 1 per 30000 to 1 per 50000 cases. With this case series, we aimed to contribute to the growing knowledge of potential clinical presentations, course and complications of congenital portosystemic shunts (CPSS) in children.
METHODS: Five children are presented in this case series: One female and four males, two with an intrahepatic CPSS and three with an extrahepatic CPSS. The first patient, who was diagnosed with an intrahepatic CPSS, presented with gastrointestinal bleeding, abdominal pain and hyperammonaemia at six years of age. He underwent a percutaneous embolization of his shunt and has remained asymptomatic ever since. The second patient presented with direct hyperbilirubinemia in the neonatal period and his intrahepatic CPSS later spontaneously regressed. The third patient had pulmonary hypertension and hyperammonaemia due to complete portal vein agenesis and underwent liver transplantation at five years of age. The fourth patient was diagnosed immediately after birth, when evaluated due to another congenital vascular anomaly, and the last patient presented as a teenager with recurrent bone fractures associated with severe osteoporosis. In addition, the last two patients are characterised by benign liver nodules; however, they are clinically stable on symptomatic therapy.
CONCLUSIONS: Abernethy syndrome is a rare anomaly with diverse clinical features, affecting almost all organ systems and presenting at any age.

Abernethy malformation is a rare congenital anomaly in which there is direct communication between the portal and systemic venous circulation. The clinical presentation ranges from asymptomatic with incidental detection on imaging to secondary complications of disease or related to associate anomalies. This is a retrospective analysis of data from nine patients with Abernethy malformation at a single center. This is a referral center for Pediatric Cardiology and for Hepatobiliary and Pancreatic Surgery. The patients presented to the Pulmonary Hypertension Clinic/the Hepatobiliary Surgery Clinic. Out of nine patients, four were male. Type II Abernethy malformation was present in five patients whereas three patients had type I malformation. One of the patients had communication between inferior mesenteric vein and internal iliac vein. Five out of nine patients were erroneously diagnosed as idiopathic primary pulmonary hypertension and were treated with vasodilators. One patient required living donor liver transplant. One patient was managed with surgical shunt closure whereas two patients required transcatheter shunt closure. The rest of the patients were managed conservatively. Abernethy malformation is more common than previously thought and the diagnosis is often missed. There are various management options for Abernethy malformation, which includes surgical or transcatheter shunt closure and liver transplant. Management of Abernethy malformation depends upon type, presentation, and size of shunt.

Abernethy malformation, also termed congenital portosystemic shunt and congenital absence of portal vein is the result of malformation of the splanchnic venous system. Congenital portosystemic shunts are divided into extra- and intrahepatic shunts. Two shunts have been defined: Type I is characterized by the complete diversion of portal blood into the vena cava with an associated congenital absence of the portal vein. Type II is defined by an intact but diverted portal vein through a side-to-side, extrahepatic connection to the vena cava. The clinical manifestations of Abernethy malformation are diverse with a typical presentation consisting of hypoxia and hepto-pulmonary syndrome. Histologically, focal nodular hyperplasia, nodular regenerative hyperplasia, liver adenoma, hepatoblastoma, and hepatocellular carcinoma have all been reported. Herein, we report a case of Abernethy malformation, type Ib, in a 12-month-old male who was found to have a small hepatocellular carcinoma at the time of explant. The immunohistochemical characteristics in relation to the genetic aspects are discussed. To our knowledge, this is the first reported case of hepatocellular carcinoma developing in a patient who is under the age of 5 years with Abernethy malformation.