Noncirrhotic Portal Hypertension: Current Concepts and Overview of Causes, Pathophysiology, and Imaging Findings

Noncirrhotic portal hypertension (NCPH) is an uncommon but important entity caused by impaired flow dynamics in the portal venous system in the absence of advanced fibrosis. The exact prevalence of this disease is unknown since many patients with NCPH are labeled as having cryptogenic cirrhosis. Numerous disease processes performed with different mechanisms can result in this entity. Based on the anatomic level of impairment of portal flow, NCPH is classified into prehepatic, intrahepatic, and posthepatic forms. The exact pathophysiology in many cases of intrahepatic NCPH is not well known, and there are overlapping terminologies used to describe histopathologic changes in the liver. The clinical and imaging findings are heterogeneous and are influenced by the mechanism and the underlying cause. In particular, patterns of portal hypertension and liver morphology are different among pre-, intra-, and posthepatic forms. All causes of NCPH can result in liver dysmorphism, but these changes are more drastic with intrahepatic and posthepatic forms (especially when associated with nodular regenerative hyperplasia) and can occasionally mimic cirrhosis. Prehepatic NCPH classically results in marked splenomegaly and large collateral formation with no ascites. On the other hand, ascites is the most common sign in posthepatic NCPH. Venographic pressure measurement and liver biopsy are required for definitive diagnosis. The authors review the current understanding of the mechanisms and causes of NCPH and discuss the approach to imaging findings, role of elastography, management, and complications.