What are the typical findings on a liver ultrasound in a patient with polycythemia vera (a myeloproliferative disorder characterized by excessive red blood cell production)?

Liver Ultrasound Findings in Polycythemia Vera

In polycythemia vera, liver ultrasound typically shows splenomegaly (present in approximately 75% of patients), and may reveal portal vein thrombosis with cavernous transformation, porto-systemic collaterals, and signs of non-cirrhotic portal hypertension—findings that reflect the vascular complications of this myeloproliferative disorder rather than primary liver parenchymal disease. 1, 2

Primary Vascular Findings

Portal Vein Abnormalities

• Portal vein thrombosis is a characteristic finding, occurring in approximately 60% of patients with PV who develop portal hypertension, and may progress to cavernous transformation 2
• The presence of porto-systemic collaterals on ultrasound is a highly specific sign of clinically significant portal hypertension and should be routinely documented 3
• Portal vein diameter may be increased, though this finding has lower diagnostic accuracy for portal hypertension 3

Hepatic Vein Assessment

• Doppler ultrasound should assess hepatic vein patency, as PV is strongly associated with Budd-Chiari syndrome (hepatic vein thrombosis), accounting for approximately 49% of all Budd-Chiari cases 1
• Non-visualization or non-opacification of hepatic veins is the hallmark finding of Budd-Chiari syndrome, though ultrasound has limitations with approximately 50% false positive/indeterminate results 1
• Doppler ultrasound remains the first-line investigation for suspected Budd-Chiari syndrome with diagnostic sensitivity >75%, superior to CT for this indication 1

Organ Size Changes

Splenomegaly

• Splenomegaly is present in approximately 36-75% of patients and is one of the most consistent ultrasound findings in PV 4, 2, 5
• All five patients in a case series of PV with non-cirrhotic portal hypertension demonstrated splenomegaly 2
• Spleen size should be measured and documented, as it contributes to risk stratification for clinically significant portal hypertension 3

Liver Appearance

• The liver parenchyma typically appears normal or shows only mild changes, as PV causes non-cirrhotic portal hypertension rather than cirrhotic changes 2
• Liver function remains relatively preserved (Child-Pugh grades A-B) even when portal hypertension develops, distinguishing this from cirrhosis-induced portal hypertension 2
• Caudate lobe hypertrophy may occur in approximately 75% of patients if Budd-Chiari syndrome develops, representing compensatory enlargement 1

Additional Ultrasound Features

Collateral Vessels

• Large intrahepatic or subcapsular collateral vessels are present in more than 80% of Budd-Chiari cases, providing strong diagnostic evidence 1
• Porto-systemic collaterals should be actively searched for and documented, as they indicate clinically significant portal hypertension and are associated with gastro-esophageal varices and worse prognosis 3

Ascites

• Ascites may be present as a manifestation of portal hypertension, though liver synthetic function typically remains preserved 2

Critical Diagnostic Considerations

When to Suspect PV from Ultrasound Findings

• Unusual thrombosis patterns (portal vein thrombosis, Budd-Chiari syndrome) in patients under 55 years without chronic liver disease should prompt evaluation for PV 1, 6
• The combination of splenomegaly, portal vein thrombosis, and preserved liver parenchyma is highly suggestive of an underlying myeloproliferative disorder 2

Limitations and Next Steps

• If Doppler ultrasound findings are equivocal for Budd-Chiari syndrome, MRI or CT should be performed focusing on specific vascular patterns rather than generalized parenchymal changes 1
• Liver biopsy is not necessary for diagnosis and should be regarded as risky in patients with suspected vascular malformations or thrombotic complications 3

Common Pitfall to Avoid

• Do not assume cirrhosis based on portal hypertension findings; PV causes non-cirrhotic portal hypertension with relatively mild liver function impairment, fundamentally different from cirrhotic portal hypertension 2
• The presence of portal hypertension signs (splenomegaly, collaterals, varices) with normal or near-normal liver parenchyma should raise suspicion for PV rather than chronic liver disease 2