Congenital hepatic fibrosis
Congenital disorders of bile acid metabolism
Metabolic diseases (e.g., alpha-1 antitrypsin deficiency)
Post-hepatic portal hypertension. It is caused by thrombosis of large or small veins draining blood from the liver into the inferior vena cava (Budd-Chiari syndrome, rare in children).
Extrahepatic portal vein obstruction can be caused by:
Thrombosis of the portal vein (Fig. 27.1): instrumentation and cannulation of the umbilical vein at birth including umbilical vein catheters for intravenous access in the first days of life, omphalitis, sepsis, hypovolemic shock and hereditary hypercoagulable states represent risk factors for this condition. Regarding the umbilical cannulation, some authors report a 40 % risk of thrombosis after the catheter is left in place for 48 hours; 100 % if more than 72 hours. Some others believe this risk has been nowadays reduced by the improvement of catheters’ materials. However the principle is that this kind of venous line must be taken into consideration only if extremely needed.
Causes of prehepatic portal hypertension: portal vein thrombosis
Portal vein congenital stenosis/atresia (Fig. 27.2a) or postnatal fibrotic stenosis (Fig. 27.2b). The latter is due to abnormal spreading of the normal process, obliterating the umbilical vein or ductus venosus of Aranzio, to the trunk of the portal vein.
Causes of prehepatic portal hypertension. (a) Atresia/stenosis of the portal vein. (b) Postnatal fibrotic stenosis
Occlusion of the main trunk of the portal vein may lead to recanalization of the vein and its transformation into a series of smaller collateral veins that assume the appearance of a venous cavernoma. It is a network of small collaterals that supply the liver with a small amount of mesenteric blood and keep the intrahepatic portal circulation patent, even though hypoplastic (Fig. 27.3). Even though the role of all these risk factors is established, in daily practice the etiology remains unknown in about 50 % of cavernomas [2–6].
Anatomic variants of cavernomas
27.3 Pathophysiology and Collateral Circulation
The main areas where the abnormal shunts between the systemic and portal venous system occur are:
Gastroesophageal area: left gastric (coronary) vein and short gastric veins to oesophageal veins (forming submucosal oesophageal varices) thence to azygous/hemiazygous veins in the thorax
Hemorrhoidal plexus in the rectum: superior hemorrhoidal veins to the middle and inferior hemorrhoidal veins and ultimately to the inferior vena cava
Paraumbilical network: paraumbilical and umbilical veins to superficial veins of the abdominal wall and the superior/inferior epigastric veins (forming the “caput medusae”)
Intestinal veins to the branches of the inferior vena cava in the retroperitoneum (veins of Retzius)
Depending on the type of Portal obstruction, every “shunting” area will be more or less developed. For instance, in the EXPVO, the paraumbilical plexus will be little represented since the umbilical veins drain beyond the obstruction (Figs. 27.4 and 27.5) .
Development of portosystemic shunts in prehepatic portal hypertension
Development of portosystemic shunt in intrahepatic portal hypertension
27.4 Clinical Presentation
Unlike children with preexisting liver disease (mainly the ones affected from cirrhosis secondary to biliary atresia), children with extrahepatic portal vein obstruction are usually completely well before the sudden onset of symptoms. The significant manifestation of portal hypertension in childhood is massive upper gastrointestinal bleeding. Oesophagogastric varices have been noted in very young infants and 70 % of patients experience their first bleeding episode before the age of 7. Almost 90 % of patients with bleeding varices secondary to extrahepatic obstruction of the portal vein hemorrhage before the age of 10 (Fig. 27.6).
(a–d) Endoscopic diagnosis of oesophageal varices
The second most common finding is splenomegaly and progressive fibrosis of the organ (fibro-congestive splenomegaly) together with a certain degree of functional hyperactivity (hypersplenism). By the term hypersplenism, we mean an excessive splenic sequestration of red and white blood cells and platelets, therefore resulting in anemia, thrombocytopenia and leukopenia.
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Routine lab parameters of liver function (transaminases, bilirubin, albumin, alkaline phosphatase, gamma-GT, PT) and splenic sequestration of cells (blood cells count) are essential. A coagulation work-up is often required if no risk factors (like an umbilical catheter) are present in order to rule out a hereditary hypercoagulable state (C and S protein, AT –III, etc.).
This could sometimes be hard to interpret because anomalies in both the pro- and anticoagulant pathway may be secondary to the hepatic deprivation of portal blood and are reversible after the successful restoration of portal flow.
The presence of a cavernoma and portal vein thrombosis are usually first diagnosed by ultrasonography with Doppler interrogation. The precise portal venous anatomy must be assessed, first by Doppler ultrasound which is suitable to demonstrate patency and flow (Fig. 27.7).
Ultrasound with Doppler interrogation for the study of portal venous anatomy and flow
Afterward patients being considered for shunting should also be evaluated by CT or MR angiography (each with its own advantages) that has replaced traditional invasive angiography except for retrograde trans-jugular portal venogram which can still be a useful tool, especially when evaluating Rex process patency (Fig. 27.8) [1–4].
CT angiography for portal anatomy assessment in a patient considered for a shunting procedure