Discussion

Abernethy malformation is defined as any congenital communication between the portal and systemic venous system.Reference Morgan and Superina ¹ In all, 8–9% of Abernethy malformations may be associated with other congenital cardiac anomalies such as heterotaxy syndromes.Reference Kothari ^{2 ,} Reference Ratnasamy, Kubegov and Swaminathan ³ The manifestations of this malformation are due to the effects of unmetabolised intestinal nitrogenous substances including ammonia on the systemic circulation causing symptoms of raised ammonia and hepatic encephalopathy. On the pulmonary vasculature, this can lead to pulmonary arterio-venous malformations or pulmonary artery hypertension.

In Abernethy malformation, typically the blood flow is from the portal system to the systemic veins. When Abernethy malformation is coexistent in a patient who has undergone Kawashima operation, the inferior caval vein reflects the pulmonary artery pressure and when the pulmonary artery pressure is elevated for any reason, flow in the malformation can be predominantly from the inferior caval vein to the portal vein. This can act as a veno-venous collateral and contribute to significant desaturation.Reference Doraiswamy and Sivakumar ⁴ The shunt can transiently reverse and flow from the portal vein to the inferior caval vein, and can cause the unmetabolised intestinal nitrogenous substances including ammonia to reach the lung, leading to pulmonary artery hypertension, which in turn can worsen the inferior caval vein to portal vein shunt. Thus, the patient can be symptomatic owing to the desaturation caused by the reversed Abernethy flow from inferior caval vein to the portal vein, as well as owing to the raised pulmonary artery pressure induced by the transient flow from the portal vein to inferior caval vein. Our patient had elevated pulmonary artery pressures (mean 16 mmHg) and significant desaturation (SaO₂ 74% in room air).

Catheter intervention of Abernethy malformation is safe and effective.Reference Knirsch, Benz and Bühr ⁵ Pre-procedure planning of closure of Abernethy malformation in heterotaxy syndrome requires detailed study of venous anatomy, as these patients may have other venous anomalies as well. The vascular plug has to be meticulously placed to avoid occluding any systemic vein. The anomalous Abernethy collateral in our patient communicated above to a tributary of the superior mesenteric vein and below to both renal veins. Therefore, the malformation was closed with a plug positioned midway between the entry of the renal veins and the superior mesenteric veins, and thus the renal veins drained to the inferior caval vein end of the channel, and the superior mesenteric vein to the portal end. Post procedure, her oxygen saturation improved from 74 to 91%. Liver function tests remained normal before the procedure and at 2 months’ follow-up.

We do not routinely prescribe anti-coagulants following vascular plug closure of Abernethy malformation. However, a patient with heterotaxy syndrome, particularly one who has undergone Kawashima procedure, is prone for venous thrombosis,Reference Kothari ² and it is advisable to start them on oral anti-coagulation and an anti-platelet medication after the procedure. Our patient developed significant inferior caval vein and portal vein thrombosis and had to be anti-coagulated with heparin. She is presently asymptomatic (at 2 months of follow-up) with an oxygen saturation of 90%, with near complete resolution of the venous thrombus, and she is on optimal anti-coagulation.