PVT is a vascular disorder involving the main portal vein and its branches, characterized by thrombus formation and extension within the portal venous system. The thrombus may propagate into the splenic or mesenteric veins, leading to varying degrees of luminal narrowing or complete occlusion (Hasan et al., 2020). The prevalence of PVT in patients with liver cirrhosis ranges from 0.6% to 16% (Senzolo et al., 2019). As a severe complication of cirrhosis, PVT exacerbates portal hypertension, increasing the risk of esophagogastric variceal bleeding and refractory ascites while reducing liver transplantation success rates and elevating mortality (Qi et al., 2015; Stine et al., 2015). The underlying mechanisms of PVT remain unclear. This study focuses on the pathogenesis of PVT, aiming to identify key factors involved in its development and provide new clinical insights for improving the prognosis of cirrhotic patients.

The pathogenesis of PVT is complex and is currently believed to result from the interplay of multiple factors, including reduced portal venous blood flow velocity, coagulation disorders, endothelial injury, and inflammatory responses (Anton et al., 2022; Huang et al., 2023). Multiple studies (Violi and Ferro, 2013; Carnevale et al., 2017; Praktiknjo et al., 2020) have shown that LPS levels in the portal circulation of cirrhotic patients are significantly higher than those in the systemic circulation. Within the portal venous system, LPS binds to Toll-like receptors (TLRs) expressed on hepatocytes and immune cells, triggering the release of large amounts of inflammatory cytokines, chemokines, vasoactive factors, adhesion molecules, and reactive oxygen species (ROS) (Custodio-Chable et al., 2020). This cascade promotes systemic inflammation, hepatic stellate cell proliferation, and the progression of liver cirrhosis (Tsuchida and Friedman, 2017). Additionally, LPS interacts with TLRs on vascular endothelial cells, platelets, and neutrophils, initiating a systemic inflammatory response and activating the coagulation cascade (Hasan et al., 2020). LPS induces oxidative stress and apoptosis in vascular endothelial cells, impairing their anticoagulant function. Endothelial dysfunction reduces nitric oxide (NO) synthesis, exacerbating vasoconstriction and worsening portal venous stasis (Bartimoccia et al., 2024).

In recent years, with the expanding field of microecology, increasing attention has been given to gut microbiota dysbiosis and its role in the pathological processes of liver cirrhosis. Studies have shown that patients with liver cirrhosis commonly exhibit significant gut microbiota dysbiosis, characterized by a marked reduction in beneficial bacteria (e.g., Bifidobacterium and Bacteroidetes) and a notable increase in opportunistic pathogens (e.g., Enterobacteriaceae and Fusobacterium) (Bajaj et al., 2014; Oh et al., 2020). The increased abundance of Gram-negative bacilli leads to elevated production of LPS in the intestinal lumen. Through mechanisms involving intestinal barrier dysfunction (gut leakage), inflammatory activation, endothelial injury, coagulation abnormalities, and hemodynamic alterations, LPS contributes to the development of PVT.

Portal venous blood serves as a critical conduit for gut microbiota entry into the systemic circulation, and its microbial composition can provide insights into the microbiological mechanisms underlying PVT. Previous studies have primarily focused on fecal microbiota, while research on circulating microbiota remains limited. This study innovatively employs 16S rRNA sequencing to systematically compare the gut, peripheral blood, and portal venous microbiota in cirrhotic patients with PVT. By analyzing microbial composition, diversity, and their associations with clinical parameters, we aim to elucidate gut-liver axis microbiome characteristics and their role in PVT development. Our findings will provide microbiological evidence for the systemic inflammation associated with PVT and offer novel perspectives on its pathogenesis.

The gut microbiota plays a crucial role in the development and progression of PVT in cirrhosis patients (Violi et al., 2023; Pemmasani et al., 2024). However, there is limited research on the characteristics of the circulatory microbiota in cirrhotic PVT patients and its relationship with the gut microbiota and the differences between them. This study explores the changes in the microbiota in the gut, portal vein, and peripheral venous blood of cirrhotic PVT patients, as well as the interactions between these microbiota in different compartments.

This study found that the gut microbiota α-diversity in the PVT group was higher than that in the NPVT group, and there was a significant difference in β-diversity between the two groups. These findings suggest a marked dysbiosis in the gut microbiota of cirrhotic PVT patients, with significant changes in the community structure of the microbiota. Huang et al. (2023) found that in cirrhotic PVT patients, the abundance of pathogenic bacteria such as anaerobes and Pseudomonas increased, while the abundance of beneficial bacteria such as Bacteroides and Weissella significantly decreased. Another study (Georgescu et al., 2023) also found that the incidence of overall microbiota dysbiosis was increased in cirrhotic PVT patients, with a significant increase in LPS + bacteria. The results of this study found that in the gut microbiota, the abundance of Gram-negative bacilli such as Escherichia-Shigella and Negativibacillus was significantly increased in the PVT group, while beneficial bacteria such as Bacteroides, Butyricicoccus, and Lachnospiraceae were significantly decreased. The Shiga toxin produced by Escherichia-Shigella can cause endothelial cell damage, leading to endothelial dysfunction and promoting thrombus formation (Siniscalchi et al., 2024). It can also lead to excessive activation of coagulation factors, triggering a systemic coagulation response (Adams et al., 2017). Studies have found that in patients with liver cirrhosis, intestinal barrier dysfunction allows Escherichia-Shigella and its produced LPS to enter the portal vein through the gut-liver axis, triggering immune responses and coagulation abnormalities, thereby promoting the formation of PVT (Nightingale and Cutler, 2013). He et al. (2022) found that Escherichia-Shigella infection significantly reduces gut microbial diversity, increases the proportion of harmful bacteria such as Proteus, and decreases beneficial bacteria such as Lactobacillus, leading to a decrease in SCFAs levels. The reduction in SCFAs is closely associated with inflammation and coagulation abnormalities. Negativibacillus is a pathogenic bacterium associated with intestinal dysbiosis or pediatric Crohn’s disease (Tang et al., 2021; Wang et al., 2021). Studies have found that Negativibacillus is significantly negatively correlated with the length of the small intestine and colon, leading to impaired intestinal development and dysfunction of the intestinal barrier in mice (Wu et al., 2021). Bacteroides is an important component of the gut microbiota. It may indirectly influence thrombosis formation by regulating intestinal barrier function and immune responses (Liu et al., 2024; Khuu et al., 2025). A study by Popescu et al. (2024) found that Bacteroides exerts anti-inflammatory effects through the production of SCFAs, which may indirectly reduce the risk of thrombosis. Huang et al. (2023) discovered that in cirrhotic PVT patients, the abundance of Bacteroides significantly decreased. Their research also showed that Bacteroides effectively reversed the formation of PVT in a rat model of cirrhosis induced by carbon tetrachloride. In this study, Bacteroides was significantly reduced in the PVT group, suggesting that Bacteroides plays a protective role in the development of cirrhotic PVT. Butyricicoccus produces butyrate, which plays a crucial role in maintaining the intestinal barrier, inhibiting intestinal inflammation, promoting immune regulation in the gut, and modulating systemic immune responses. Butyrate has been shown to regulate the inflammatory response and oxidative stress in endothelial cells by inhibiting histone deacetylases (HDACs), processes that are important in thrombosis formation (Umei et al., 2021). In cirrhotic PVT patients, the gut microbiota is severely dysregulated, primarily characterized by an increase in Gram-negative pathogenic bacteria and a decrease in beneficial SCFA-producing bacteria. Modulating the gut microbiota may serve as a potential therapeutic strategy to alleviate symptoms and improve prognosis in cirrhotic PVT patients.

The dysregulated gut microbiota in cirrhosis can translocate into the bloodstream through the compromised intestinal barrier, further influencing the microbiome in the portal vein and peripheral vein. The blood microbiome is primarily dominated by Proteobacteria, with low concentrations of Actinobacteriota, Bacteroidota, and Firmicutes, consistent with previous studies (Iebba et al., 2018; Alvarez-Silva et al., 2019; Schierwagen et al., 2019). In this study, no significant differences were found in the α and β diversity of the peripheral venous microbiota between the PVT and NPVT groups, suggesting that the peripheral venous microbiota in cirrhotic PVT patients remains relatively stable and is not influenced by the gut microbiota. However, significant differences were observed in the α and β diversity of the portal venous microbiota. As the central pathway of the “gut-liver axis,” the microbiota of the portal vein directly reflects the effects of gut microbiota translocation, while the peripheral venous microbiota remains relatively stable due to liver filtration and systemic immune clearance. LEfSe analysis revealed that Massilia was significantly increased in the portal circulation of the tPVT group. Massilia, a Gram-negative bacterium, has been shown in a study to have a higher relative abundance in the blood microbiome of patients with cirrhosis and chronic hepatitis C, especially in those whose hepatic venous pressure gradient has not decreased, and it is significantly associated with inflammation and plasma biomarkers of metabolism (Virseda-Berdices et al., 2022). Park and Shin (2013) isolated Massilia from the tympanic membrane exudate of patients with otitis media. Additionally, Massilia has been identified in the femurs of patients with osteomyelitis, in the eyes of patients with endophthalmitis, in the cerebrospinal fluid of patients with pseudotumors, as well as in the blood of patients with cerebellar lesions, end-stage renal disease, sepsis, and common variable immunodeficiency—conditions associated with immune dysfunction (La Scola et al., 1998; Lindquist et al., 2003; Kämpfer et al., 2012). Furthermore, studies have indicated that overgrowth of Massilia in cases of dysbiosis may exacerbate inflammation (Aghamajidi and Maleki Vareki, 2022; Maciel-Fiuza et al., 2023). Given the commonly observed immunosuppressed state in patients with cirrhosis and PVT, we observed a significant enrichment of Massilia in their portal vein blood, suggesting a potential link to local inflammatory responses or the status of the coagulation system. However, there is currently no direct evidence indicating a pathogenic role of Massilia in the formation of PVT. Further studies incorporating functional experiments are needed to explore the potential mechanistic role and clinical significance of this genus in the pathogenesis of PVT.

The gut microbiome has been utilized as a novel molecular biomarker, with previous studies evaluating diagnostic accuracy based on liver fibrosis/cirrhosis-associated bacteria and metabolomic characteristics, yielding effective results (AUC: 0.72–0.91) (Loomba et al., 2019; Lee et al., 2020). The present study found that the AUC values of fecal microbiome and portal vein biomarkers were 0.78 and 0.95, respectively, both demonstrating good diagnostic value. In contrast, the AUC of peripheral venous biomarkers was 0.43, indicating that portal vein microbiome is the optimal biomarker for diagnosing PVT. The high AUC value highlights the crucial role of the “gut-portal vein-liver” axis in thrombosis formation. Portal vein microbiome detection shows potential clinical value in the early diagnosis of PVT. However, this analysis is exploratory in nature and the observed AUC should be interpreted with caution. The identified microbial features should be validated in larger, independent cohorts to confirm their diagnostic potential and reproducibility.

Liver diseases are closely related to gut microbiome translocation. Schierwagen et al. (2019) found strong evidence of bacterial translocation, showing that in patients with decompensated cirrhosis, the bacteria in different circulatory compartments (portal vein, hepatic vein, and central vein) are similar. Iebba et al. (2018) discovered that the microbiome composition in the portal vein blood of cirrhotic patients resembles that of the cecal mucosa, suggesting that the portal vein microbiome may originate from gut microbiome translocation. Effenberger et al. (2023) found that DNA from the fecal microbiome was significantly enriched in the blood and liver tissues of patients with liver cancer and cirrhosis, compared to patients with non-alcoholic fatty liver disease (NAFLD). The Venn diagram results of this study show that the tPVT group has more shared bacterial genera between the portal vein and feces compared to the tNPVT group, indicating a more significant abnormal translocation of gut microbiota into the portal venous system in patients with PVT. This suggests a more severe impairment of the intestinal barrier function in cirrhotic PVT patients, leading to a greater amount of gut microbiota entering the portal venous system. The shared microbiota between the portal vein, peripheral vein, and feces in the tPVT group primarily consists of pathogenic bacteria such as Escherichia-Shigella, Veillonella, Streptococcus, Bacillus, Klebsiella, and Haemophilus. Veillonella can work synergistically with Streptococcus to release endotoxins and inflammatory factors, thereby damaging the intestinal barrier function (Mashima and Nakazawa, 2014). In the gut microbiota, many facultative anaerobes (such as Streptococcus) can survive and proliferate in oxygen-rich living tissues. When the intestinal barrier weakens or their numbers increase, these bacteria can translocate from the intestinal contents to the intestinal wall and further spread into the bloodstream (Arab et al., 2018; Ponziani et al., 2018; Jin et al., 2022). Pathogenic bacteria and pro-inflammatory cytokines (such as TNF-α, IL-6) released from the intestinal inflammatory microenvironment can migrate to the liver through the portal venous system, exacerbating the process of liver cirrhosis and fibrosis (Arab et al., 2018; Skinner et al., 2020). The findings of this study suggest that pathogenic bacteria from the inflamed gut microenvironment may translocate to the liver via the portal venous system, potentially playing a critical role in the development and progression of PVT. Our research team plans to integrate data on gut and portal vein microbiota composition, inflammatory markers, and coagulation function to construct a personalized PVT risk assessment model, providing a basis for early clinical intervention. Strategies aimed at improving gut barrier function or modulating microbial composition—such as the use of probiotics, fecal microbiota transplantation, or targeted antibiotics—hold promise for preventing bacterial translocation and the spread of inflammatory mediators, thereby delaying or even preventing the onset of PVT. However, the feasibility and safety of these diagnostic and therapeutic approaches require further validation through large-scale clinical studies and mechanistic investigations.

Spearman rank correlation analysis was used to assess the relationship between the microbiota and clinical parameters. In the tPVT group, the majority of portal vein microbiota in portal vein blood showed significant positive correlations with LPS and FVIII. LPS can activate the NF-κB signaling pathway by binding to TLR4, prompting monocytes, endothelial cells, and other cells to release pro-inflammatory factors (such as TNF-α, IL-6, IL-1β) (Khuu et al., 2025). These inflammatory factors can activate the coagulation system, thus promoting the formation of PVT. Iebba et al. (2018) found that in cirrhotic patients, both peripheral blood and portal vein blood mainly consisted of p_Proteobacteria, and the presence of p_Proteobacteria members was positively correlated with the levels of IL-6, IL-1β, and TNF-α. Georgescu et al. (2023) reported a significant increase in LPS + bacteria in cirrhotic PVT patients, with a significant correlation between LPS + bacteria and biomarkers (such as D-Dimer, CRP, and TNF-α), as well as with the severity of PVT. In the study of the relationship between intestinal microbiota and blood parameters in the tPVT group, it was found that Faecalibacterium, Ruminococcus, Bacteroides, Eubacterium_hallii_group, Agathobacter, and Romboutsia were significantly negatively correlated with the Child-Pugh score, suggesting that these bacteria may have a protective role in maintaining liver metabolism and immune stability. Additionally, Faecalibacterium, Ruminococcus, Bacteroides, Eubacterium_hallii_group, Alistipes, Agathobacter, Blautia, and Subdoligranulum were negatively correlated with the MELD score, indicating that dysbiosis could be an important feature of liver function deterioration. Subdoligranulum was positively correlated with LPS in the portal vein, and studies have shown that intestinal bacteria Subdoligranulum can drive the production of systemic autoantibodies, antibody deposition at joint centers, and immune activation, thus triggering rheumatoid arthritis in at-risk populations (Chriswell et al., 2022). This genus is associated with elevated endotoxins, suggesting that it may be involved in the process of intestinal barrier dysfunction and endotoxin translocation.

This study is the first to detect gut-liver ecological dysregulation associated with cirrhosis-related PVT and elucidates the role of the intestinal and circulating microbiomes, supporting the hypothesis that microbial imbalance may promote the development of PVT. To validate these findings, future studies will expand the sample size and identify more biomarkers to assist with early diagnosis and treatment of PVT. Additionally, animal models and genomics can be utilized to investigate how microbial imbalance influences PVT formation through immune modulation, intestinal barrier dysfunction, and endotoxin translocation, further exploring the role of gut-liver axis ecological dysregulation in PVT.