Applications of percutaneous mechanical thrombectomy in transjugular intrahepatic portosystemic shunt and portal vein thrombosis.

Portal vein thrombosis (PVT) is an uncommon cause for presinusoidal portal hypertension. PVT can be caused by one of three broad mechanisms: (1) spontaneous thrombosis when thrombosis develops in the absence of mechanical obstruction, usually in the presence of inherited or acquired hypercoagulable states; (2) intrinsic mechanical obstruction because of vascular injury and scarring or invasion by an intrahepatic or adjacent tumor; or (3) extrinsic constriction by adjacent tumor, lymphadenopathy or inflammatory process. Usually, several combined factors are necessary to result in PVT. The consequences of portal vein thrombosis are mostly related to the extension of the clot within the vein. Gastrointestinal bleeding from gastroesophageal varices is the most frequent presentation. Noninvasive imaging techniques are currently used for the screening of patients and the initial diagnosis of PVT. The invasive techniques are reserved for cases when noninvasive techniques are inconclusive, before percutaneous interventional treatment, or in preoperative assessment of patients who are candidates for surgery. Recanalization of the portal vein with anticoagulation alone may not be consistent or appropriate in highly symptomatic patients. Catheterization of the superior mesenteric artery (SMA) is helpful for diagnosis as well as for therapy by allowing the intra-arterial infusion of thrombolytic drugs in the same setting. Direct transhepatic portography allows precise determination of the degree of stenosis and extension within the portal vein, as well as pressure measurements. Thrombotic occlusions of the portal, mesenteric, and splenic veins can be managed by mechanical thrombectomy (MT) or pharmacologic thrombolysis. Underlying occlusions because of organized or refractory thrombus or fixed venous stenosis are best corrected by balloon angioplasty and stent placement. Access into the portal venous system can also be established through creating a transjugular intrahepatic portosystemic shunt (TIPS). Creating a TIPS is also important in the setting of PVT associated with cirrhosis to decompress portal hypertension and improve portal venous flow. PVT involving the portal, splenic, and/or mesenteric veins can also complicate a preexisting TIPS in which case the shunt can be readily used as therapy access. Several techniques may be used to recanalize the shunt and portal venous system, including thrombolytic therapy, balloon angioplasty/embolectomy, suction embolectomy, basket extraction of clots, and mechanical thrombectomy with a variety of devices. Advantages of MT include the potential to rapidly remove thrombus without the need for prolonged thrombolytic infusions, and reducing the potential life-threatening complications of thrombolytic therapy. Possible drawbacks include the risk of intimal or vascular trauma to the portal vein, which may promote recurrent thrombosis.