Anticoagulation Strategy and Timing in Primary Antiphospholipid Syndrome–Associated Splanchnic Vein Thrombosis: A Systematic Review.

Portal vein thrombosis and other forms of splanchnic vein thrombosis associated with primary antiphospholipid syndrome are rare but potentially severe, with substantial morbidity from thrombus progression/recurrence and complications of portal hypertension, and with clinically important bleeding risk under anticoagulation. Despite the central role of anticoagulation in antiphospholipid syndrome, there remains uncertainty regarding the optimal anticoagulant strategy (unfractionated or low-molecular-weight heparin, vitamin K antagonists, direct oral anticoagulants, sequential regimens, treatment duration and INR targets) and, critically, the timing of initiation in recent versus chronic disease (including cavernomatous transformation), where the benefit–risk balance may differ. The available evidence is dispersed across small observational studies and heterogeneous populations, limiting confident clinical decision-making. This systematic review will synthesize the existing evidence on effectiveness (recanalization, progression/recurrence) and safety (major bleeding, mortality) according to anticoagulation strategy and timing in adults with primary antiphospholipid syndrome–associated splanchnic vein thrombosis. By also capturing clinically relevant portal hypertension outcomes (e.g., varices/variceal bleeding, cavernoma, portal biliopathy, and need for TIPS or shunt procedures), the review aims to clarify comparative outcomes, identify knowledge gaps, and inform both practice and the design of future studies in this rare phenotype.