Extrahepatic Portal Vein Obstruction

Abstract

Extrahepatic portal vein obstruction (EHPO) is a frequent cause of portal hypertension in children, but it also occurs in adults as a sequela to portal thrombosis. In infants, omphalitis and other forms of infection are the established causes, and in adults pylephlebitis, biliary tract infection, and injury to the portal vein during surgery are known to be associated with EHPO. The etiology is more often obscure in adult cases while in infants there may be only cavernous transformation in the absence of a recognizable portal vein remnant, and a congenital malformation or agenesis cannot be ruled out as a possible etiology. For this reason, some investigators divide this disease into primary and secondary types, but we believe that even in infant cases the majority are due to portal thrombosis, and separation of the two types is difficult and of little significance. One of the important questions regarding its etiopathology is whether EHPO and intrahepatic noncirrhotic portal hypertension (also called hepatoportal sclerosis, idiopathic portal hypertension, and noncirrhotic portal fibrosis) are two entirely different disorders or the same disease with differing sites of primary involvement [1]. Portal vein thrombosis is frequently seen in patients with the latter disorder, and some of the patients with EHPO present the same features seen in the latter [2]. In India, both noncirrhotic portal hypertension and EHPO are very common. In 1975, a research committee was founded in Japan under the auspices of the Japan Ministry of Health and Welfare to study the epidemiology, etiology, clinical features, and management of idiopathic portal hypertension and related disorders. One of the authors (K.O.) was the chairman of this research committee, and this group continues to study these problems. The two first national surveys were conducted in 1983, one for idiopathic portal hypertension (IPH) and the other for EHPO [2]. In 1987, second national surveys were carried out for more recent cases by the other author (HA). In this chapter, therefore, we wish to present the analyses of the two national surveys on EHPO in Japan made by this study group, and a review of the past studies on portal vein obstruction, mainly of the chronic type.