Can polycythemia vera (PV) cause an inferior mesenteric venous varix, particularly in a patient with a history of thrombotic events?

Can Polycythemia Vera Cause Inferior Mesenteric Venous Varix?

Yes, polycythemia vera (PV) can cause inferior mesenteric venous varix through its well-established association with splanchnic vein thrombosis, which leads to portal hypertension and subsequent development of venous varices including those in the mesenteric circulation. 1

Mechanism of Varix Formation in PV

Polycythemia vera is the most common acquired risk factor for splanchnic vein thrombosis (SPVT), which encompasses portal, mesenteric, and splenic vein thrombosis. 1 The pathophysiology involves multiple prothrombotic mechanisms:

• Hyperviscosity from elevated hematocrit creates low shear rates in large veins, enhancing thrombogenic interactions between platelets, leukocytes, and endothelial cells 1
• Qualitative platelet defects including increased thromboxane A2 production and abnormal platelet activation contribute to the baseline prothrombotic state 1
• JAK2V617F mutation (present in >95% of PV patients) is detected in 20-40% of patients with SPVT even without overt myeloproliferative disease 1, 2

Development of Varices from Thrombosis

When mesenteric vein thrombosis occurs in PV patients, chronic thrombosis leads to formation of collateral veins (portal cavernoma) and portal hypertension, which manifests as splenomegaly and varices including esophageal and mesenteric venous varices. 1

• Chronic SPVT is often asymptomatic due to collateral vein formation, but the presence of splenomegaly and/or esophageal varices indicates established portal hypertension 1
• Complications from variceal bleeding can occur in these patients, with gastrointestinal bleeding reported in 5% of cases 1

Clinical Recognition in Patients with Thrombotic History

In a patient with PV and a history of thrombotic events, the risk of splanchnic vein involvement is particularly elevated. 1, 3, 2 Key considerations:

• Thrombotic events occur in 16% (arterial) and 7% (venous) of patients prior to or at PV diagnosis, with venous events frequently involving unusual sites like splanchnic veins 2
• The highest rates of thrombosis occur shortly before or at diagnosis and decrease over time with treatment 3
• Underlying myeloproliferative neoplasms require indefinite anticoagulation for splanchnic vein thrombosis 1

Diagnostic Approach

When evaluating a mesenteric venous varix in a PV patient, confirm the diagnosis with CT angiography (CTA) or MR venography, as these modalities best evaluate vascular structure, venous patency, and identify complications like bowel ischemia. 1

• Duplex ultrasonography may be limited by overlying bowel gas for mesenteric veins 1
• The presence of portal cavernoma on imaging indicates chronic thrombosis 1
• Test for JAK2V617F mutation if not previously done, as it has diagnostic and prognostic implications 1

Management Implications

All PV patients should receive therapeutic phlebotomy to maintain hematocrit <45% and low-dose aspirin (100 mg daily) to reduce thrombotic risk. 4, 5, 2

• High-risk patients (age ≥60 years or prior thrombosis) require cytoreductive therapy with hydroxyurea or interferon-alpha in addition to phlebotomy and aspirin 5, 3, 2
• For established SPVT with underlying myeloproliferative neoplasm, anticoagulation should be given indefinitely with vitamin K antagonists 1
• Hematocrit must be maintained <45% as levels above this threshold are associated with progressive vascular occlusive episodes 5

Critical Pitfall to Avoid

Do not assume that adequate phlebotomy alone prevents all thrombotic complications. While phlebotomy substantially reduces thrombosis risk, it does not abolish it, and factors beyond hematocrit (platelets, leukocytes, endothelial dysfunction) continue to contribute to thrombotic risk. 1 Patients with prior thrombosis require both optimal hematocrit control AND cytoreductive therapy to minimize recurrent events. 5, 3