Extrahepatic portosystemic shunts (EPS) are abnormal vascular communications between the portal and systemic venous systems, often emerging in the context of liver cirrhosis and portal hypertension. While variceal EPS, such as esophageal and gastric varices, are well-recognized, non-variceal EPS (NVEPS) remain underdiagnosed and misunderstood despite their clinical significance. This review synthesizes the latest knowledge on the pathogenesis, classification, diagnosis, complications, and management of NVEPS.
Introduction
EPS are broadly classified into congenital and acquired types. Congenital forms are rare and unrelated to cirrhosis or portal hypertension. Acquired EPS, commonly seen in adults with cirrhosis, include both variceal and non-variceal subtypes. NVEPS are de novo aberrant vascular connections formed via neoangiogenesis due to sustained portal hypertension. These shunts, which include splenorenal, gastrorenal, mesocaval, and portocaval variants, may initially offer decompression benefits but often lead to hepatic decompensation due to reduced hepatic perfusion.
Epidemiology and Classification
NVEPS are more prevalent than previously assumed, with imaging studies estimating their presence in up to 80% of cirrhotic patients. Classification schemes consider size (with 8 mm as the threshold), anatomical position (left- vs. right-sided), and drainage pattern (superior vs. inferior vena cava). NVEPS predominantly drain into the inferior vena cava, differentiating them from variceal EPS.
Pathogenesis
While initially attributed to mechanical pressure changes, recent insights emphasize the role of neoangiogenesis driven by vascular endothelial growth factor and other mediators like nitric oxide. This pathological remodeling initiates a feedback loop of hypoperfusion, tissue hypoxia, and further collateral formation. Consequently, NVEPS contribute to the development of portosystemic shunt syndrome, marked by progressive hepatic dysfunction, encephalopathy, and worsening Child-Pugh scores.
Diagnosis
Noninvasive imaging is essential for diagnosing NVEPS. Doppler ultrasound offers initial assessment but has limitations in detecting small or deep shunts. Contrast-enhanced CT and MRI provide superior sensitivity and anatomical detail, with CT favored for its speed and resolution.
Clinical Presentation and Complications
The clinical manifestations of NVEPS depend on shunt location. While splenorenal and mesorenal shunts commonly present with hepatic encephalopathy (HE), gastrorenal shunts are often associated with bleeding gastric varices. Other complications include ascites and portal vein thrombosis (PVT), though data on these associations remain inconsistent. Notably, the presence and size of NVEPS are independent risk factors for HE, particularly in patients with preserved liver function.
Management Strategies
Timely intervention in NVEPS is crucial to preventing hepatic decompensation. Interventional radiologic embolization, including balloon-, plug-, and coil-assisted retrograde obliteration techniques, is effective for managing HE and bleeding. These approaches have shown high rates of symptom resolution and improved portal flow. However, risks such as ascites and esophageal variceal bleeding necessitate careful patient selection and risk stratification based on MELD and Child-Pugh scores.
NVEPS and TIPS
The relationship between NVEPS and transjugular intrahepatic portosystemic shunt (TIPS) procedures is complex. While TIPS aims to reduce portal pressure, coexisting NVEPS may persist post-procedure and compete for blood flow, exacerbating HE. Emerging evidence suggests that concurrent embolization of NVEPS during TIPS can significantly reduce HE incidence without affecting other outcomes like shunt patency or mortality.
NVEPS and Liver Transplantation
NVEPS may complicate liver transplantation by diverting portal flow from the graft, leading to dysfunction and higher PVT risk. Surgical ligation of large shunts during transplantation has shown benefits in reducing postoperative complications and improving survival. However, some studies argue for a conservative approach, noting spontaneous regression of NVEPS post-transplant and lack of negative impact on outcomes.
Conclusion
NVEPS represent a significant but often overlooked contributor to hepatic decompensation in cirrhosis. Their pathogenesis involves active vascular remodeling rather than passive pressure-related dilation. Timely diagnosis using advanced imaging and appropriate interventional strategies are key to improving outcomes. Management must be individualized, considering the dynamic interplay between liver function, portal pressure, and the presence of collateral circulation. Future research should refine treatment algorithms and explore long-term impacts on liver transplantation outcomes.
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The study was recently published in the Journal of Clinical and Translational Hepatology .
The Journal of Clinical and Translational Hepatology (JCTH) is owned by the Second Affiliated Hospital of Chongqing Medical University and published by XIA & HE Publishing Inc. JCTH publishes high quality, peer reviewed studies in the translational and clinical human health sciences of liver diseases. JCTH has established high standards for publication of original research, which are characterized by a study's novelty, quality, and ethical conduct in the scientific process as well as in the communication of the research findings. Each issue includes articles by leading authorities on topics in hepatology that are germane to the most current challenges in the field. Special features include reports on the latest advances in drug development and technology that are relevant to liver diseases. Regular features of JCTH also include editorials, correspondences and invited commentaries on rapidly progressing areas in hepatology. All articles published by JCTH, both solicited and unsolicited, must pass our rigorous peer review process.
