Rare Causes of Portal Vein Thrombosis and Occlusion: A Narrative Review.

Portal vein thrombosis (PVT) refers specifically to the presence of a thrombus within the main portal vein trunk or its intrahepatic branches. In contrast, portal vein occlusion encompasses a broader spectrum of conditions, including tumor invasion, external compression and disorders that predispose to thrombosis, such as thrombophilia or inflammatory states. Advanced liver disease, particularly cirrhosis, is the most common cause of PVT, primarily due to portal hypertension, altered hemostasis and hemodynamic changes, followed by malignancies and inherited or acquired thrombophilic conditions. In contrast to these common etiologies, our clinical experience has highlighted rare causes of portal vein obstruction associated with typical presentations, which pose diagnostic challenges. Examples include acute PVT during transjugular intrahepatic portosystemic shunt (TIPS) placement and non-thrombotic porto-mesenteric obstruction related to portal venous gas. While these events may appear unexpected, they represent a recognizable group of uncommon causes rather than isolated incidents. PVT can present as an acute or chronic condition: acute thrombosis is characterized by recent thrombus formation and potential intestinal ischemia, whereas chronic thrombosis is associated with long-standing obstruction, cavernous transformation and portal hypertension. This narrative review integrates a comprehensive literature search with clinical experience, with particular emphasis on uncommon etiologies of portal vein obstruction.