Off the beaten track: finding a route for embolization of a liver haemangioma in a neonate

What is congenital hepatic haemangioma?

According to the classification of the International Society for the Study for Vascular Anomalies (ISSVA), congenital hepatic haemangioma (or congenital haemangioma of the liver) is a benign endothelial vascular tumour that proliferates in utero and reaches its peak size around the perinatal period. It has a similar natural history as congenital haemangioma in other anatomic locations and may be subclassified as rapidly involuting (RICH), partially involuting (PICH), and non-involuting congenital haemangioma (NICH).

The clinical spectrum of congenital hepatic haemangioma is highly variable, ranging from asymptomatic incidental finding to life-threatening high output cardiac failure. Some of the congenital haemangioma may be detected on prenatal imaging as the fetus may develop hydrops. In addition to heart failure, the dilated vascular spaces within the haemangioma can cause anaemia, thrombocytopaenia and hypofibrinogenaemia, leading to bleeding diathesis.

On imaging, congenital hepatic haemangioma usually manifests as a unifocal mass (in contradistinction to infantile hepatic haemangioma which is more common in multifocal or diffuse form). Intralesional calcification, central scarring or fibrosis are also important diagnostic clues for congenital hepatic haemangioma. Dynamic contrast imaging demonstrates avid peripheral nodular enhancement followed by gradual centripetal fill-in.

By one year of age, most RICHs will be reduced to about 80% of their original size and appear as small calcified lesions.

Since rapidly involuting congenital haemangioma (RICH) will regress on its own, why do we need to intervene?

For RICH, the involution phase usually occurs around 2 to 3 months after birth, before which the high flow arteriovenous shunting within the congenital hepatic haemangioma can cause life-threatening complications – most notably high-output cardiac failure. If left untreated, the high-output state would lead to a vicious cycle of pulmonary hypertension, right heart failure, arterial hypoxaemia and ultimately multi-organ failure. In contrast to infantile hepatic haemangioma, propranolol has no effect on congenital haemangioma. If there is significant high flow shunting, medical therapy such as fluid restriction, diuretics, and steroids may not be able to tide the neonate over the critical period.

Embolization of the feeding arteries of the haemangioma can be life-saving in this scenario. The goal of embolization is not to occlude ALL arterial feeders, but to occlude the most sizeable ones in order to reduce the arteriovenous shunting to a manageable level. Use of coil and histoacryl glue have been described for trans-arterial occlusion of high flow shunts in congenital haemangioma.

However, performing vascular interventions and embolization in neonates can be challenging. Firstly, the amount of iodinated contrast that can be administered is limited. In a 2kg neonate, the upper limit of undiluted iodinated contrast is around 8 to 10mL. Secondly, the neonatal circulatory volume is small (around 200mL in a 2kg neonate). Injudicious use of saline flush or blood loss from other complications can easily lead to clinically significant anaemia. Lastly and most importantly, the neonatal arteries are very small. Gaining vascular access for intervention can be very difficult. In addition, the relatively large sheath-to-vessel ratio may also lead to increased access site complications such as arterial occlusion and limb ischemia.

The arteries in neonates are so small, what are the options for accessing them?

While femoral arteries are commonly accessed for vascular interventions in adults, they may not be the best options for neonates. In our case, the femoral arteries measure only around 1.2 to 1.5mm. The infrarenal aorta is also small in size, limiting the use of reverse curve catheters. The cannulation of the downward sloping celiac artery is anticipated to be difficult with a forward-facing catheter.

Alternative arterial access routes have been described, including the left axillary artery and carotid artery. Both of these arteries present a better “attack” angle for the celiac artery from above. Their calibers are also slightly larger than the femoral artery. However, these access routes are not without potential severe complications, including upper limb ischemia, pseudoaneurysms and nerve injury with trans-axillary access; and stroke with trans-carotid access.

One elegant solution for neonatal arterial access is to exchange a pre-existing umbilical artery catheter (UAC) with a vascular sheath. UAC is commonly placed in critically ill neonates by neonatologists soon after delivery and can be kept in-situ for up to one week. Unfortunately, a UAC was not available in this case and the umbilical artery had already involuted.

Physiological shunts between arterial systems and venous systems from the foetal circulation may persist into neonatal period, i.e. patent ductus arteriosus (PDA) and patent foramen ovale. These shunts present unique opportunities for interventional radiologists to access the arterial system from the venous side. Larger vascular sheaths can be used in veins and the risk of post-access haematoma is also reduced compared to conventional arterial access. In my presentation, I will show how the arterial system can be accessed via the PDA, using the “up-and-over” technique.