[Venous thrombosis at unusual sites]

Venous thrombosis at unusual sites such as the upper extremity, the splanchnic and cerebral veins, and rarer ovarian, renal and retinal sites has long been managed in analogy to lower-limb deep vein thrombosis because dedicated trials were lacking. This has changed substantially. The 2023 German S2k guideline now addresses these sites explicitly, and a growing body of randomized and prospective evidence supports the use of direct oral anticoagulants (DOACs). For upper-extremity thrombosis, therapeutic anticoagulation is first-line and is managed according to deep vein thrombosis. A functioning, still-needed catheter can remain in situ. For splanchnic vein thrombosis, anticoagulation reduces recurrence and mortality and improves recanalization, including in cirrhotic portal vein thrombosis (Child-Pugh A/B). In cirrhotic portal vein thrombosis DOACs are possible depending on the liver function (rivaroxaban/edoxaban in Child A, apixaban in Child B, low molecular weight heparin in Child C). A JAK2-V617F screen identifies an underlying myeloproliferative neoplasm before blood-count changes appear and should be part of the etiological work-up of a non-cirrhotic splanchnic vein thrombosis. For cerebral venous thrombosis, DOACs have shown to be as effective as vitamin K antagonists with fewer major, particularly intracranial, bleeds, while vaccine-induced immune thrombotic thrombocytopenia (VITT) requires non-heparin anticoagulation. For ovarian, renal and retinal veins, robust data remains absent. This article summarizes the practice-relevant advances for the general internist, focusing on the upper extremity and the splanchnic veins.