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

Abstract

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.

Introduction

Congenital portosystemic shunts (CPSS) are rare vascular malformations classified as either extrahepatic or intrahepatic. Extrahepatic CPSS, also known as Abernethy malformations, were first described by John Abernethy in 1793[1]. These anomalies are associated with serious long-term complications, including portopulmonary hypertension, hepatic atrophy, hyperammonemia, and hepatic encephalopathy.

HIGHLIGHTS

• Congenital portosystemic shunts (CPSS) are rare vascular malformations resulting from persistent embryonic venous connections between the portal and systemic circulations.

• An extrahepatic CPSS (Abernethy malformation) may lead to serious complications such as portopulmonary hypertension and hepatic encephalopathy.

• The branchless intraparenchymal portal vein trunk draining into the right atrium has not previously been described.

• Diagnosis relies heavily on imaging modalities, as clinical findings are often nonspecific.

• Management is shunt type-dependent: Type II lesions may undergo shunt closure, whereas Type I lesions often require conservative care or liver transplantation.

Globally, fewer than 330 cases have been reported to date[2]. Here, we present a 7-year-old female with a portal vein that courses unusually through the hepatic parenchyma without giving rise to any intrahepatic branches and then drains directly into the right atrium. To the best of our knowledge, this anatomic variant of a branchless intraparenchymal portal vein trunk draining into the right atrium has never been described before. This case underscores the importance of early recognition, careful evaluation, and tailored management of these rare anomalies.

This case is reported in accordance with the SCARE 2025 guidelines[3].

Case presentation

A 7-year-old girl presented to our outpatient department for a routine general examination. She had no significant complaints except for occasional mild fatigue during sports activities. There was no history of jaundice, abdominal distension, gastrointestinal bleeding, or recurrent infections. Developmental milestones were appropriate for her age.

Physical examination

The child appeared well, active, and in no distress. Vital signs were within normal limits, and growth parameters were age-appropriate. There was no pallor, jaundice, or cyanosis. Cardiovascular examination revealed normal heart sounds with no murmurs. Respiratory and neurological examinations were unremarkable. The abdomen was soft and non-tender, with no hepatosplenomegaly or ascites.

Investigations

Echocardiography revealed a small atrial septal defect (ASD) and a patent ductus arteriosus (PDA). Triphasic contrast-enhanced computed tomography (CT) of the abdomen demonstrated the portal vein coursing through the liver without branching and draining directly into the right atrium (Figs 1–3). The child’s liver function tests and coagulation profile were within normal limits. Based on the imaging, she was diagnosed with Type Ib Abernethy syndrome.

Figure 2.

Coronal CT image demonstrating the portal vein directly draining into the right atrium (arrow).

Figure 1.

(A) Axial CT image showing the portal vein passing through the liver without branching (green arrow). (B) Portal vein draining directly into the right atrium (red arrow).

Figure 3.

Diagrammatic illustration of Type Ic Abernethy syndrome.

Clinical course:

Given her mild symptoms and the absence of significant portosystemic complications, the patient was managed conservatively with close multidisciplinary follow-up. She remains stable, with periodic clinical and imaging monitoring planned.

Discussion and literature review

Embryology and pathogenesis

CPSS result from abnormal vascular communications between the portal and systemic veins due to failure of involution in one or more primordial venous vessels. In humans, the hepatic venous architecture develops between the fourth and sixth weeks of gestation. The vitelline, cardinal, and umbilical veins are the three embryonic venous systems that form a transient network inside and outside the liver, leaving no permanent communication between the portal and systemic circulation except for the ductus venosus (DV)[4].

Epidemiology and classification

CPSS are exceptionally rare, with an estimated prevalence of 1 in 30 000 to 50 000 births, and by 2022, over 320 cases had been documented globally[5]. CPSS frequently coexist with other congenital anomalies, particularly cardiovascular malformations, as well as with various syndromes such as Down syndrome[6].

CPSS are classified as intrahepatic or extrahepatic portosystemic shunts (EHPS). Extrahepatic CPSS, also known as Abernethy malformations, were further classified into two broad categories – Types I and II – by Morgan and Superina in 1994. Type I is an end-to-side shunt with a complete absence of intrahepatic portal venous branches. It is further divided into Types Ia and Ib. In Type Ia, the splenic vein and the superior mesenteric vein (SMV) drain separately into the systemic venous system, and, in Type Ib, the two veins form a common trunk before systemic drainage^[4,7^]. Type II describes partial shunts in which some portal flow persists into the liver. There are three subtypes: IIa, corresponding to portohepatic shunts and the DV; IIb, shunts arising from the main portal vein (MPV) from the splenomesenteric confluence to the portal bifurcation; and IIc, shunts arising from the mesenteric, gastric, or splenic veins[8]. The majority of the reported cases are extrahepatic or portocaval shunts.

Uniqueness of the present case

In our patient, the splenic vein and SMV form a common portal trunk that traverses the hepatic parenchyma without giving rise to any intrahepatic portal branches and ultimately drains directly into the right atrium. This does not conform to the typical Type Ib configuration. To our knowledge, this intraparenchymal but branchless portal venous course with direct right-atrial drainage has not been previously described. Given its distinct anatomic pattern, we propose that this represents a novel subtype – Type Ic Abernethy malformation.

Clinical manifestations

The fundamental problem in Abernethy syndrome is the diversion of portal venous flow away from the liver, depriving hepatocytes of the trophic signals and substrates normally delivered through the portal system. This disruption affects metabolic activity, cellular regeneration, and overall hepatic architecture, gradually leading to underdeveloped or atrophic liver parenchyma[9].

CPSS presents with a wide clinical spectrum, and no single feature is diagnostic. Detection may occur in utero, incidentally, or after the onset of complications. Reported manifestations can be grouped into three broad categories: (1) findings related to associated congenital malformations; (2) consequences of impaired hepatic development, such as fatty infiltration or benign nodular transformation; and (3) symptoms attributable to portosystemic shunting, including hyperammonemia, hepatic encephalopathy, hepatopulmonary syndrome, and pulmonary vascular complications, which may lead to significant hypoxemia and cyanosis[10]. The most frequent functional disturbance is hepatic encephalopathy[4]. Other complications include renal anomalies, cardiomyopathy, gastrointestinal bleeding, hypoglycemia, and benign or malignant hepatic masses, including focal nodular hyperplasia, adenoma, hepatocellular carcinoma, or hepatoblastoma[2].

Our patient remained largely asymptomatic, apart from mild exertional dyspnea, and was found to have small congenital cardiac anomalies (PDA and ASD) during the evaluation.

Imaging

Given the nonspecific nature of clinical and laboratory findings in Abernethy syndrome, imaging plays a central role in establishing the diagnosis and guiding management. Doppler ultrasonography is typically the initial modality for assessing shunts, liver morphology, nodules, and associated malformations[11]. CT and MRI provide high-resolution delineation of the portal and systemic venous anatomy, enabling detailed vascular mapping and evaluation of potential complications^[11,12^].

Before intervention, evaluating the extra- and intrahepatic portal veins using angiography with temporary balloon occlusion is strongly recommended as it helps differentiate side-to-side EHPS from end-to-side, which is crucial for the management. The rise in portal pressure under temporary occlusion guides procedural planning. Shunt flow or shunt index (SI), which correlates with hyperammonemia and encephalopathy, can be quantified using nuclear medicine techniques such as rectal scintigraphy[13]. A decrease in SI was associated with an increase in shunt diameter in EHPS[14]. Evaluation of intrapulmonary shunts, pulmonary hypertension, and neurologic involvement with further imaging is warranted[15].

Management

The management strategy for CPSS depends primarily on the anatomic type and the presence of symptoms or complications[16]. Many portohepatic shunts detected in infancy close spontaneously within the first year of life; therefore, conservative observation is appropriate for selected asymptomatic neonates and infants[17]. Symptomatic or life-threatening shunts generally require intervention^[1,16^].

In the management of Type II Abernethy syndrome, shunt closure is possible because some intrahepatic portal flow is preserved. Percutaneous or transcatheter shunt closure is achieved using vascular plugs, coils, and variable shunt occluder devices[18]. In scenarios where endovascular therapy fails or is not available, surgical ligation or banding is indicated^[6,19^]. Most of the complications resolve or regress after shunt closure. Benign liver tumors regress, hepatopulmonary syndrome improves, and neurological symptoms normalize in most cases[18]. Occasionally, persistence of portopulmonary hypertension has been observed, but no new complications have been reported after shunt occlusion[9].

In Type I Abernethy malformation, however, shunt closure is not feasible due to the lack of intrahepatic portal branches, and the only definitive treatment is liver transplantation. While awaiting transplantation, supportive care to control hyperammonemia, hepatic encephalopathy, and other multisystem issues is crucial. Most of the neurologic, hepatic, and cardiopulmonary complications resolve after liver transplantation^[9,20^].

Given that our patient had an absence of intrahepatic portal veins, mild clinical symptoms, and minor associated cardiac anomalies, the multidisciplinary team opted for conservative management with close clinical surveillance. The patient has remained clinically stable during follow-up. Our case highlights the role of conservative management in asymptomatic patients with Type I Abernethy syndrome, consistent with findings reported in previous case studies[21].

Conclusion

Abernethy syndrome is a rare but important cause of noncirrhotic portal hypertension and multisystem complications that impact the neurological, hepatic, and pulmonary systems. Early recognition, thorough imaging, and individualized management, with shunt closure (either surgically or through interventional radiology) in Type II and transplantation in symptomatic Type I, offer the best outcomes. Our case highlights the importance of detailed vascular evaluation and the role of careful observation in asymptomatic patients with Type I Abernethy malformation.

Ethical approval

Protection of human and animal subjects. The authors declare that the procedures followed were in accordance with the regulations of the relevant clinical research ethics committee and with those of the Code of Ethics of the World Medical Association (Declaration of Helsinki).

Confidentiality of data. The authors declare that they have followed the protocols of their work center regarding the publication of patient data.

Consent

Written informed consent was obtained from the patient for publication of this case report and accompanying images.

Sources of funding

This case report received no specific grant from any funding agency.

Author contributions

Z.A.A.: Conceptualization, Validation, Writing – original draft, Writing – review & editing. Z.A.S.: Conceptualization, Validation, Writing – original draft, Writing – review & editing. A.G.W.: Writing – original draft. All authors have read and approved the final manuscript and agree to be accountable for all aspects of the work.

Conflicts of interest disclosure

The authors declare no conflicts of interest.

Research registration unique identifying number (UIN)

Not applicable.

Guarantor

Zeki A. Abubeker.

Provenance and peer review

Not commissioned; externally peer reviewed.

Data availability statement

All relevant data supporting the findings of this case report are included within the article. No additional datasets were generated or analyzed.

Disclosure statement

The authors declare that they have no financial or personal relationships that could have inappropriately influence or bias the work reported in this article.