Several mechanisms may contribute:

1. Increased cell traffic and sequestration
2. With elevated blood cell production and turnover, the spleen may have more filtering/processing demand. [3]
3. Extramedullary hematopoiesis (more typical of advanced-stage disease)
4. As myeloproliferative disease evolves—especially with progression toward a myelofibrosis phenotype—blood cell production can occur outside the marrow, commonly in the spleen, contributing to enlargement. [3,8]
5. Vascular/congestive factors
6. Myeloproliferative neoplasms carry thrombotic risk; vascular complications and congestion can contribute to abdominal symptoms, and (uncommonly) splenic infarction can occur. [2,9]

Many patients have no symptoms. When present, symptoms may include:

• Fullness, pressure, or discomfort under the left ribs
• Early satiety (feeling full after small meals)
• Bloating
• Pain (occasionally, acute pain may relate to complications such as infarction) [4,9]

Note: These symptoms are not specific to PV; other conditions can also enlarge the spleen. [4]

Splenomegaly can be a marker of disease burden and may correlate with symptoms. In PV follow-up, clinicians track spleen size along with blood counts, symptoms, and other clinical features. [1,2,5]

• Stable or mild enlargement can occur without immediate danger.
• Progressive enlargement may prompt reassessment of disease control and evaluation for evolution toward a post-PV myelofibrosis phenotype (in a subset of patients). [2,5,8]

Typical evaluation includes:

• Physical exam (palpation)
• Ultrasound or CT when clarification or more precise measurement is needed [1,7]
• Concurrent PV assessment (CBC trends, symptoms, and hematology review per guideline-based care) [1,2]

1. Can polycythemia cause an enlarged spleen?

Yes. In PV, splenomegaly is a recognized clinical feature. [1,2]

2. Is spleen enlargement dangerous?

Often it is manageable, but a markedly enlarged spleen can cause symptoms and, rarely, complications. Seek prompt evaluation for sudden severe left-upper abdominal pain. [4,9]

3. How do I know if my spleen is enlarged?

A clinician may detect it on physical exam, and imaging (ultrasound/CT) can confirm size more precisely. [1,7]

4. What should I avoid if I have an enlarged spleen?

Clinicians often advise avoiding activities that risk abdominal trauma and seeking care for acute pain; specific recommendations should be individualized by the treating team. [4]

PV — Polycythemia vera

CBC — Complete blood count

CT — Computed tomography

FAQs — Frequently asked questions

1. McMullin, M. F., Harrison, C. N., Ali, S., Cargo, C., Chen, F., Ewing, J., … Mead, A. J. (2019). A guideline for the diagnosis and management of polycythaemia vera: A British Society for Haematology Guideline. British Journal of Haematology, 184(2), 176–191. https://doi.org/10.1111/bjh.15648
2. Tefferi, A., & Barbui, T. (2023). Polycythemia vera: 2024 update on diagnosis, risk-stratification, and management. American Journal of Hematology, 98(9), 1465–1487. https://doi.org/10.1002/ajh.27002
3. Song, M. K., Park, B. B., & Uhm, J. E. (2018). Understanding Splenomegaly in Myelofibrosis: Association with Molecular Pathogenesis. International journal of molecular sciences, 19(3), 898. https://doi.org/10.3390/ijms19030898
4. Mayo Clinic. (2025). Polycythemia vera—Symptoms & causes. https://www.mayoclinic.org/diseases-conditions/polycythemia-vera/symptoms-causes/syc-20355850
5. Silver, R. T., Erdos, K., Taylor, E., 3rd, Scandura, J. M., & Abu-Zeinah, G. (2023). Splenomegaly (SPML) in polycythemia vera (PV): its clinical significance and its relation to symptoms, post-polycythemic myelofibrosis (PPMF) and survival. Leukemia, 37(3), 691–694. https://doi.org/10.1038/s41375-022-01793-w
6. Grunwald, M. R., Stein, B. L., Boccia, R. V., Oh, S. T., Paranagama, D., Parasuraman, S., Colucci, P., & Mesa, R. (2018). Clinical and Disease Characteristics From REVEAL at Time of Enrollment (Baseline): Prospective Observational Study of Patients With Polycythemia Vera in the United States. Clinical lymphoma, myeloma & leukemia, 18(12), 788–795.e2. https://doi.org/10.1016/j.clml.2018.08.009
7. Lee, M. W., et al. (2022). Volumetric splenomegaly in patients with polycythemia vera. Journal of Korean Medical Science, 37, e87. https://doi.org/10.3346/jkms.2022.37.e87
8. Cenariu, D., Zdrenghea, A.-A., Pop, B., et al. (2021). Extramedullary Hematopoiesis of the Liver and Spleen. Journal of Clinical Medicine, 10(24), 5831. https://doi.org/10.3390/jcm10245831
9. Abdalla, E., Musa, M., Musa, M., Hatem, A., Fadul, A., & Ahmed, A. O. (2022). Splenic Infarctions in Polycythaemia Vera are Not Always a Catastrophe. European journal of case reports in internal medicine, 9(6), 003370. https://doi.org/10.12890/2022_003370