Anatomical patterns and collateral pathways in congenital aplasia, atresia, and hypoplasia of iliac and lower extremity veins: a retrospective cohort study.

PURPOSE: Congenital aplasia, atresia, and hypoplasia of the iliac and lower extremity veins are rare vascular anomalies characterized by disrupted venous drainage and compensatory collateralization. Despite the clinical significance of these anomalies, their embryological origins, anatomical patterns, and hemodynamic consequences remain understudied. This study aimed to elucidate the anatomical variability, collateral pathways, and clinical implications of these anomalies through a single-center retrospective analysis.

METHODS

Chinese patients with lower extremity congenital capillary-venous malformations and deep venous aplasia/atresia/hypoplasia were included. Imaging protocols included color Doppler ultrasound in all cases, supplemented by magnetic resonance and/or computed tomography venography in selected cases.

RESULTS

An evaluation of the patient demographics demonstrated a male predominance (male:female, 40:24), mean age of 6.9 ± 6.7 years (2 months to 33 years), and 59.4% of cases in childhood (2-12 years) at referral. Anatomical patterns included left-sided iliac vein aplasia (36 left and 31 right cases) with frequent multi-segment defects (58%). Severe cases included deep vein aplasia (12%) and saphenous system anomalies (22%). Five key collateral pathways were identified: 1) superficial cross-pubic, great saphenous vein (GSV) → pudendal veins → contralateral GSV; 2) deep pelvic, internal pudendal → obturator → internal iliac veins; 3) ascending trunk, thoracoepigastric → axillary veins; 4) marginal systems, gluteal-external vertebral networks; and 5) reflux-driven collaterals mimicking post-thrombotic syndrome.

CONCLUSION

Congenital iliac and lower extremity venous anomalies demonstrated left-sided and male predominance and complex collateralization. The observed anatomical patterns, including the persistence of embryonic veins, provide a practical framework for distinguishing compensatory collaterals from pathological vessels.