Portosystemic Anastomoses: A Narrative Review of Anatomy, Clinical Significance of Spontaneous Portosystemic Shunts, and Contemporary Therapeutic Approaches.

Portosystemic anastomoses represent natural or acquired vascular communications between the portal venous system and the systemic circulation, which under physiological conditions constitute vessels of minimal flow and no clinical significance, yet become dilated and develop in states of portal hypertension, predominantly in the context of liver cirrhosis. This narrative review aims to elucidate the complex and essentially dual role of these anastomoses, with particular focus on the spontaneous portosystemic shunts (SPSS) that develop in cirrhotic patients, their clinical significance, and the contemporary therapeutic approaches developed for their management. A systematic literature search was conducted across PubMed/MEDLINE, Scopus, and Google Scholar (from September 2025 to July 2026), without language restrictions, using MeSH terms and free-text keywords including "portosystemic anastomoses," "spontaneous portosystemic shunts," "portal hypertension," "hepatic encephalopathy," "TIPS," and "BRTO." A structured search strategy was applied, incorporating Boolean operators (AND/OR). No formal quantitative synthesis (meta-analysis) was performed. This is a narrative review synthesising published findings from eligible studies. A total of 847 initial records were identified, 644 were screened after duplicate removal, 123 were assessed for full-text eligibility, and 46 studies were ultimately included. The synthesis of the literature reveals that portosystemic anastomoses are anatomically classified into oesophagogastric, anorectal, paraumbilical, and retroperitoneal types, with the spontaneous splenorenal shunt (SSRS) representing the most commonly identified large SPSS in advanced cirrhosis. The presence of SPSS, particularly when their total shunt area (TSA) exceeds 83 mm², is independently associated with an increased risk of hepatic encephalopathy (HE) and mortality, regardless of the Child-Pugh or Model for End-stage Liver Disease (MELD) score. The relationship between SPSS and variceal bleeding is complex and counterintuitive, as the presence of SPSS does not appear to confer protection against haemorrhagic events. Therapeutic management relies primarily on the transjugular intrahepatic portosystemic shunt (TIPS) and on selective embolisation techniques, including balloon-occluded retrograde transvenous obliteration (BRTO), plug-assisted retrograde transvenous obliteration (PARTO), and coil-assisted retrograde transvenous obliteration (CARTO), while surgical shunts retain a role in selected patient categories. This review concludes that portosystemic anastomoses are not a neutral imaging finding but an active participant in the natural course of cirrhosis, with an initially compensatory yet ultimately detrimental character. Their recognition, quantification, and individualised management are critical parameters in the contemporary clinical approach to the patient with cirrhosis and portal hypertension.