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Background
Catheter-based interventions are relatively rare in the pediatric population but serve as an invaluable tool in managing many pathologies. There are several hepatic lesions seen during the neonatal or infantile period and indications for intervention vary depending on the underlying pathology. Abnormal tumor vascularity may result in cardiac, pulmonary, renal, or hematologic dysfunction that compromises the patient while simultaneously increasing the risks of emergent surgery. In many cases, catheter-based embolization is the safest approach to stabilizing these patients prior to consideration of major surgical intervention. Transarterial embolization for hepatic lesions is a commonly performed procedure in adults, which is typically performed via a common femoral or radial artery puncture. In neonates, the femoral artery is small in caliber, making cannulation technically difficult. These arteries are even more diminutive in premature neonates, and in this patient population, the umbilical artery is an ideal vessel for arterial access.

Educational Goals / Teaching Points
Brief overview of vascular tumors in the neonatal setting. Clinical presentation and significance of Kasabach-Merritt phenomenon Management of neonatal vascular tumors. Highlight challenges and complications of femoral and carotid artery access in neonates. Review indications, uses, and limitations of umbilical venous and arterial catheters. Multimodal case review of umbilical artery access for embolization of a large hepatic vascular tumor.

Key Anatomic/Physiologic Issues and Imaging Findings/Techniques
Neonates requiring a complex embolization typically reside in the neonatal intensive care unit (NICU) and often have indwelling umbilical venous (UVC) and arterial catheters (UAC) placed at birth to monitor blood pressure, sample blood, and infuse fluids or administer medications. Typically, the umbilical artery regresses within hours of birth, but if catheterized, the artery remains patent for 7 - 10 days, which creates a window for interventional procedures to be performed safely via a simple catheter exchange. There are few case reports of this access utilized for diagnostic angiography and interventions for unstable neonates, often in the setting of vascular malformations or vascular tumors. Certain lesions, such as AVMs, may require multiple interventions and effort should be made to preserve femoral access for future interventions.

Conclusion
The management of critically ill premature neonatal patients requires careful consideration and a multidisciplinary team. When intervention is required, the umbilical artery offers safe vascular access with a lower complication profile than direct femoral cannulation. More so, patients in the NICU setting often already have an indwelling UAC in place. Therefore, in neonates with indwelling UACs that may require an interventional procedure, the risk-benefit analysis warrants leaving the artery accessed as long as feasible. Multidisciplinary conversations involving the interventionalist are important in reiterating that indwelling UAC cannulation can provide safe and reliable access for life-saving intervention.