Congenital portosystemic shunts (CPSS) are rare vascular anomalies with abnormal connections between the portal and systemic venous systems, diverting portal blood away from the liver. This can lead to hyperammonemia (with or without encephalopathy), hepatopulmonary syndrome, portopulmonary hypertension, and liver nodules/tumors – often without portal hypertension. Advances in Doppler ultrasound, CT angiography, and MRI have improved detection and classification. Treatment depends on shunt type and severity, ranging from interventional embolization to surgical ligation. Most persistent or symptomatic shunts require intervention. Emerging genetic and embryological insights are shedding light on pathogenesis. This review summarizes current knowledge on CPSS epidemiology, pathophysiology, clinical presentation, diagnosis, and management, and highlights the need to consider CPSS in patients with unexplained hepatic encephalopathy or liver disease.
Introduction
CPSS are rare vascular anomalies from aberrant fetal development, causing partial or complete diversion of portal blood away from the liver. They are classified as intrahepatic (IHPS) or extrahepatic (EHPS, historically Abernethy malformations). Estimated incidence is 1 in 30,000–50,000 live births, though true prevalence is uncertain due to underdiagnosis. CPSS may be detected incidentally or during evaluation for congenital heart disease, syndromic conditions, or after onset of characteristic symptoms.
Pathogenesis
Genetics : Studies in dogs with IHPS identified impaired aryl hydrocarbon receptor (AHR) pathway signaling, with a LINE-1 insertion in the AHR gene reducing expression. IHPS and EHPS show distinct hepatic gene expression profiles (e.g., VCAM1, WEE1), suggesting different developmental pathways. Association with human congenital anomalies (heterotaxy, heart disease, microdeletions) supports a genetic component.
Embryology : CPSS arise from incomplete involution of embryonic venous structures (umbilical, cardinal, vitelline veins) during weeks 4–6 of gestation. Failure of ductus venosus closure leads to persistent shunting.
Clinical Presentations
Pediatric : Neonatal cholestasis (~32%), hepatopulmonary syndrome (~3–18%), portopulmonary hypertension (PoPH), neurocognitive dysfunction/hepatic encephalopathy (17–30%), and liver nodules/tumors (27.8%, more common in EHPS).
Adult : Hepatic encephalopathy (28% by age 30), PoPH (7–14%), hepatopulmonary syndrome, benign/malignant liver tumors (focal nodular hyperplasia, adenomas, HCC). Cumulative incidence of at least one major manifestation reaches 58% by age 40. Liver synthetic function is usually preserved; portal hypertension is uncommon unless concurrent liver disease exists.
Diagnosis
Doppler ultrasound : First-line imaging, can detect shunts and regenerative nodules.
MRI/CT : Preferred for precise anatomy. MRI avoids radiation and is superior for visualizing hepatic nodules; hepatobiliary contrast agents increase sensitivity.
Angiography with occlusion testing : Essential for preoperative planning. Measures portal pressure change during temporary shunt occlusion. A rise <10 mmHg favors single-stage closure; higher values suggest staged or partial closure. Portosystemic pressure gradient (PSPG) is preferred over absolute portal pressure.
PoPH screening : Echocardiography (if >50 mmHg or right heart dysfunction, then right heart catheterization).
Neurocognitive testing : Psychometric hepatic encephalopathy score (PHES), critical flicker frequency, continuous reaction time, inhibitory control test, Stroop test.
Treatment
Early intervention is recommended for persistent shunts beyond infancy, symptomatic presentations, or lack of portal vein visualization. Intrahepatic shunts may close spontaneously by age 1 year. All extrahepatic or persistent intrahepatic shunts beyond 1 year should be closed.
Endovascular treatment (first choice) : Transcatheter embolization with coils or vascular plugs. Staged closure with reducing stent or modified plug if portal pressures are high. Associated with shorter procedure time, less blood loss, favorable outcomes. Preferred for long, narrow shunts.
Surgical treatment : Ligation (single-stage or two-stage). Required for short, broad shunts, when endovascular access is not feasible, or after failed radiological intervention. Bicêtre classification guides approach.
End-to-side shunts (Abernethy type I) often require two-stage closure.
Side-to-side shunts (Abernethy type II) can be closed in one stage.
Medical therapy for complications : For PoPH: endothelin receptor antagonists, PDE5 inhibitors, prostacyclin analogues.
Liver resection or transplantation : For large or malignant tumors, failed occlusion test, severe underlying liver disease, or severe portal hypertension.
Conclusions
CPSS are rare but important causes of hepatic encephalopathy without cirrhosis, hepatopulmonary syndrome, PoPH, and liver tumors. Genetic and embryological insights are emerging. Management requires multidisciplinary evaluation, occlusion testing, and individualized approach (endovascular vs. surgical, single-stage vs. staged). Screening for CPSS should be considered in young patients with unexplained hepatic encephalopathy in the absence of portal hypertension.
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The study was recently published in the Journal of Clinical and Translational Hepatology .
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Journal of Clinical and Translational Hepatology
Congenital Portosystemic Shunts: A Review
4-Feb-2026