The prevalence of PVT in patients with cirrhosis is unclear, with a wide variety of incidence claimed by various researchers (estimated to be 1 in 100 by some while others believe it affects nearly 1 in 4).Thrombophilia (including inherited conditions such as factor V Leiden deficiency, protein C or S deficiency, or antiphospholipid antibody syndrome) is another common cause. Nearly one-third of patients have a myeloproliferative disorder (e.g. polycythemia vera or primary thrombocytosis), most commonly due to a Janus kinase 2 (JAK2) gene mutation. Oral contraceptive use or pregnancy are other non-inherited tendencies for thrombosis.Alternatively, the portal vein may be injured as a result of pancreatitis, diverticulitis, cholangiocarcinoma, hepatocellular carcinoma (HCC), or abdominal surgery/trauma. Red flags for cancerous growth as a cause are elevated alpha fetoprotein levels, portal vein diameter greater than 2.3 cm, pulsatility on Doppler ultrasound imaging, or hyperintense hepatic arterial phase (HAP) on CT scan with contrast.PVT is also a known complication of surgical removal of the spleen. During the last several years, myeloproliferative neoplasms (MPNs) have emerged as a leading systemic cause of splanchnic vein thromboses (which include PVT). Mechanism
The main portal vein is formed by the union of the splenic vein and superior mesenteric vein (SMV). It is responsible for approximately three-fourths of the liver’s blood flow, transported from much of the gastrointestinal system as well as the pancreas, gallbladder, and spleen. Cirrhosis alters bleeding pathways thus patients are simultaneously at risk of uncontrolled bleeding and forming clots.
A long-standing hindrance in flow as in chronic PVT, also known as portal cavernoma, can cause an increase in the hepatic venous pressure gradient (portal hypertension) and increased blood flow through subsidiary veins. This may lead to ascites or bleeding from varices.An infected thrombus may become septic, known as pylephlebitis; if blood cultures are positive for growth at this time, the most common organism is Bacteroides. Diagnosis
The diagnosis of portal vein thrombosis is usually made with imaging confirming a clot in the portal vein; ultrasound is the least invasive method and the addition of Doppler technique shows a filling defect in blood flow. PVT may be classified as either occlusive or nonocclusive based on evidence of blood flow around the clot. An alternative characterization based on site can be made: Type 1 is limited to the main portal vein, Type 2 involves only a portal vein branch (2a, or 2b if both branches are affected), and Type 3 if clot is found throughout both areas. Determination of condition severity may be derived via computed tomography (CT) with contrast, magnetic resonance imaging (MRI), or MR angiography (MRA). Those with chronic PVT may undergo upper endoscopy (esophagogastroduodenoscopy, EGD) to evaluate the presence of concurrent dilated veins (varices) in the stomach or esophagus. Other than perhaps slightly elevated transaminases, laboratory tests to evaluate liver function are typically normal.