What causes pelvic venous congestion?

Causes of Pelvic Venous Congestion

Primary Pathophysiologic Mechanisms

Pelvic venous congestion results from three main mechanisms: venous valvular insufficiency causing reflux, mechanical venous obstruction, and hormonal factors—with ovarian and internal iliac vein reflux being the most common causes. 1

Venous Reflux and Valvular Insufficiency

• Ovarian vein incompetence is the predominant cause, characterized by retrograde (caudal) flow in dilated ovarian veins (≥8 mm diameter) due to valvular insufficiency 2, 1
• Internal iliac vein reflux contributes to pelvic congestion by allowing retrograde flow into the pelvic venous plexus 1, 3
• The condition typically manifests as dilated periuterine and periovarian veins with slow or reversed blood flow (<3 cm/s) 2

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 2, 1
• May-Thurner syndrome involves compression of the left common iliac vein by the right common iliac artery, creating venous obstruction that leads to pelvic congestion 1, 4
• Nonthrombotic iliac vein lesions (NIVL) cause focal stenosis of the common iliac vein or inferior vena cava, with intravascular ultrasound often revealing severe compression not apparent on standard venography 2, 1, 4
• The combination of gonadal vein reflux and nonthrombotic iliac vein lesions produces more severe symptoms than either condition alone 1

Hormonal Factors

• Estrogen overstimulation plays a significant contributory role by promoting increased blood flow to pelvic organs and indirectly regulating nitric oxide-mediated smooth muscle relaxation in pelvic vessels 2, 1
• Many women with pelvic congestion demonstrate morphologic findings of polycystic ovarian syndrome (enlarged ovaries with exaggerated central stroma and multiple small peripheral follicles) without typical clinical features like hirsutism or amenorrhea 2, 1
• Symptoms may subside after menopause in some women due to decreased estrogen stimulation 2, 1

Anatomical Variants and Rare Causes

• Median sacral vein incompetence represents a rare but documented cause of pelvic congestion, particularly in cases of recurrent symptoms after ovarian vein embolization 5
• Recurrence of pelvic congestion can occur through alternative tributaries in the venous network even after successful treatment of primary sources 5
• Large cross-pelvic collaterals may develop secondary to chronic venous obstruction, perpetuating the congestion 5, 4

Clinical Context and Associated Conditions

• The condition occurs predominantly in multiparous women, suggesting that pregnancy-related venous changes contribute to development 6, 7
• Pelvic congestion frequently coexists with lower extremity varicose veins of pelvic origin, particularly affecting the posterior thigh, vulva, and inguinal regions through venous escape points from the internal iliac system 2, 1
• The pathophysiology likely involves a combination of genetic predisposition, anatomical abnormalities, damage to vein walls, and venous hypertension 7

Important Clinical Pitfall

A critical diagnostic consideration: nonthrombotic obstruction of the left common iliac vein or inferior vena cava is an underappreciated cause that should be carefully evaluated in all patients presenting with pelvic congestion, as treatment of obstruction alone may resolve symptoms even when ovarian vein reflux is present but left untreated 4. Standard ultrasound and CT may suggest only moderate compression, while intravascular ultrasound reveals severe focal stenosis requiring stenting 4.