A novel variant of Type I Abernethy syndrome: branchless intraparenchymal portal vein trunk draining into the right atrium in a 7-year-old girl: a case report and literature review.

INTRODUCTION AND IMPORTANCE: Abernethy malformations, also known as extrahepatic congenital portosystemic shunts, are uncommon vascular anomalies that can result in significant long-term complications. This case underscores the diagnostic challenges they present and highlights the importance of detailed multimodal imaging and timely diagnosis. CASE PRESENTATION: We describe a rare vascular anomaly in a 7-year-old girl with exertional dyspnea. Imaging revealed an unprecedented variant of the Abernethy malformation: the portal vein traversing the liver without intrahepatic branches and draining directly into the right atrium. The patient remains clinically stable under close surveillance. CLINICAL DISCUSSION: Type I Abernethy malformations are defined by the complete absence of intrahepatic portal venous arborization. However, the intraparenchymal - but branchless - portal vein observed in our patient, with direct drainage into the right atrium, does not align with existing subtypes. Given its distinct anatomic pathway and potential implications for diagnosis, classification, and management, we propose this configuration as a novel subtype: Type Ic Abernethy malformation. Stable patients with limited associated anomalies can be safely managed conservatively. CONCLUSION: Abernethy syndrome is a rare congenital vascular anomaly that may result in unpredictable multisystem complications. Clinicians should consider it in children with unexplained cardiopulmonary symptoms or atypical hepatic vascular anatomy. Recognition of previously undescribed variants, such as the proposed Type Ic, is essential for improving classification accuracy and guiding individualized management. Early identification remains crucial to prevent serious sequelae.