What causes an enlarged ovarian vein?

Causes of Enlarged Ovarian Vein

Enlarged ovarian veins result from five primary mechanisms: ovarian vein incompetence with valvular insufficiency (the most common cause), pregnancy-related changes and postpartum thrombosis, mechanical venous compression syndromes, hormonal factors (particularly estrogen overstimulation), and pelvic inflammatory/infectious processes. 1

Primary Pathophysiological Mechanisms

Ovarian Vein Incompetence

• Valvular insufficiency is the predominant cause, characterized by retrograde flow in dilated ovarian veins measuring ≥8 mm in diameter 1
• The condition manifests as dilated periuterine and periovarian veins with slow or reversed blood flow (<3 cm/s) 1
• This leads to pelvic congestion syndrome, where engorged and refluxing pelvic veins cause chronic venous pooling 1

Pregnancy and Postpartum Complications

• Ovarian vein thrombosis complicates 0.01 to 0.18% of pregnancies, typically peaking 2-6 days after delivery or miscarriage 2
• The right ovarian vein is involved in 70-80% of cases due to compression of the inferior vena cava and dextrorotation of the uterus during pregnancy 3
• Antegrade flow and multiple incompetent valves in the right ovarian vein favor bacterial infection and thrombosis 3
• Postpartum ovarian vein thrombosis presents with acute abdominal pain, fever, and an enlarged ovarian vein with endoluminal thrombus 4

Mechanical Venous Obstruction

• Nutcracker syndrome occurs when the left renal vein is compressed between the superior mesenteric artery and aorta, causing increased pressure that transmits to pelvic veins via the left ovarian vein 1
• May-Thurner syndrome involves compression of the left common iliac vein by the right common iliac artery, causing venous obstruction leading to pelvic congestion 1
• Nonthrombotic iliac vein lesions (NIVL) cause focal stenosis of the common iliac vein or inferior vena cava, with severe compression often not apparent on standard venography 1

Hormonal Factors

• Estrogen overstimulation plays a significant contributory role by promoting increased blood flow to pelvic organs 1
• Estrogen indirectly regulates nitric oxide-mediated smooth muscle relaxation in pelvic vessels, potentially contributing to venous pooling 1
• Many women with pelvic congestion have morphologic findings of polycystic ovarian syndrome (enlarged ovaries with exaggerated central stroma and multiple small peripherally located follicles) without typical clinical features 1
• Symptoms may subside after menopause due to decreased estrogen stimulation 1

Infectious and Inflammatory Causes

• Pelvic inflammatory disease, endometritis, and pelvic infections are recognized risk factors for ovarian vein enlargement and thrombosis 2, 3
• Active infection was present in 61.7% of pregnancy-related ovarian vein thrombosis cases 5
• Ovarian vein thrombosis can be the cause of puerperal fever in approximately one-third of women 2

Additional Risk Factors

Thrombotic and Hypercoagulable States

• In 4-16% of cases, ovarian vein thrombosis can be classified as idiopathic 2
• Thrombophilia was detected in 20% of pregnancy-related and 42.9% of non-pregnancy-related ovarian vein thrombosis cases 5
• Hypercoagulation conditions including antiphospholipid syndrome, systemic lupus erythematosus, factor V Leiden, and protein C and S deficiency are recognized risk factors 3

Iatrogenic and Surgical Causes

• Recent pelvic or gynecological surgeries are common risk factors 2, 3
• Oral contraceptives contribute to ovarian vein thrombosis risk 2

Malignancy-Associated Enlargement

• Malignancies are a recognized risk factor, with ovarian vein thrombosis often an incidental finding at abdominal imaging in oncological patients 2

Clinical Pitfall

The right ovarian vein's preferential involvement (70-80% of cases) is often mistaken for appendicitis or other right-sided pathology, requiring high clinical suspicion and appropriate imaging to establish the correct diagnosis 2, 3.