The current study was the first to identify metabolic biomarkers that could be used to predict esophageal VNT in cirrhotic patients using 1H-MR spectroscopy in conjunction with their relationships with the clinical variables of spleen diameter, platelet count, and the ratio of platelet count to spleen diameter. We found that hepatic lactate + TG and choline content measured using 1H-MRS strongly correlated with esophageal variceal bleeding, which is one of the complications of liver cirrhosis. In multivariate analysis, the 1H-MR spectroscopic signal intensities of both lactate + TG and choline were associated with the potential risk factors of age, spleen diameter, platelet count, and the ratio of platelet count to spleen diameter in cirrhotic patients with and without VNT. Our findings, therefore, demonstrate the value of 1H-MRS as a diagnostic tool in vivo to evaluate possible esophageal variceal bleeding as well as provide valuable information for understanding the cellular alterations in hepatic metabolism related to progressive EV in cirrhotic liver disease. If 1H-MRS is included in routine MR imaging protocols for the screening and surveillance of VNT or management of liver cirrhosis, it could provide a better targeted, more cost-effective strategy of diagnostic and therapeutic endoscopy in cirrhotic patients.
As an interesting feature of hepatic metabolite differences, the lactate + TG level was significantly higher in cirrhotic patients with VNT than in cirrhotic patients without VNT, indicating that esophageal variceal bleeding induced by cirrhosis could be associated with elevated lactate levels in conjunction with progressive hepatic dysfunction. Although the lactate signal at 1.3 ppm overlapped with large TG resonance in the liver and could not be separated from TG peak in our spectra , we assumed that lactate contributed to differential patterns of metabolite changes between cirrhotic liver with and without VNT, similar to previous studies [11, 12] of in vivo 1H-MRS with a long TE, which have demonstrated a disease-specific lactate + TG signal intensity. The liver plays an important role in modulating cellular homeostatic pathways such as the metabolism of organic acid anions including lactate and amino acids [19, 20]. However, in chronic liver diseases, lactate clearance is impaired due to a reduction of functional hepatocytes, while healthy liver has a major functional reservoir of metabolizing lactate [19, 20]. Several studies [19, 21, 22] using hyperpolarized 13C-MRS with liver disease models reported that the lactate-to-pyruvate ratio could be used as a metabolic marker indicating an inadequate supply of oxygen and glucose, suggesting that higher lactate levels compared with normal controls are induced by hypoxic and hypermetabolic states under anaerobic glycolysis in pathological states. More importantly, our study demonstrated that hepatic metabolite values for lactate + TG were associated with the presence of esophageal VNT. However, the relationships between the metabolic parameters and the endoscopic findings of EVs have been poorly investigated. A recent study  reported that the presence of EVs and the risk of developing variceal bleeding correlated with the severity of cirrhosis. Enomoto et al.  reported the association of the branched-chain amino acids to tyrosine ratio (BTR) with the severity of liver fibrosis and EVs in patients with hepatitis C virus-positive chronic liver disease. In that study, a decreased value of BTR was found to be associated with the progression of liver fibrosis and severity of varices.
Given the results of our correlation analysis, spleen diameter was positively correlated with lactate + TG level in both cirrhotic patients without VNT and with VNT, as well as in the combined group of cirrhotic patients without/with VNT. These positive correlations indicate that any increase in spleen diameter was associated with higher levels of hepatic metabolites, and therefore with impaired metabolic status associated with the progression of EV as well as the presence of esophageal VNT. Additionally, in the combined group of cirrhotic patients without/with VNT, platelet count was negatively correlated with lactate + TG level, suggesting that higher levels of hepatic metabolites could be related to the severity of impaired metabolic status, which might be associated with the development of esophageal VNT in patients with cirrhotic liver. Therefore, the increased lactate + TG level might be a noninvasive metabolic biomarker reflecting disease-specific metabolism in the hepatic pathophysiology to predict the occurrence of esophageal VNT or to help determine an effective follow-up strategy.
Our results also revealed that in cirrhotic patients with VNT, the choline metabolite levels were significantly higher than those in cirrhotic patients without VNT. Choline is an important constituent of the cell membrane in phospholipid metabolism and is an active marker of cellular proliferation, indicating that an elevated choline peak may be associated with increased membrane phospholipid biosynthesis . Given the altered level of choline-containing compounds including choline, phosphocholine, glycerophosphocholine, and taurine in cirrhotic liver, a previous study  reported that alterations of choline-containing compounds may suggest abnormal synthesis or degradation of cell membranes, or may just be related to the mobility of the choline-containing compound parts. In our correlation analysis, choline levels were positively correlated with spleen diameter in both cirrhotic patients without VNT and with VNT, as well as in the combined group of cirrhotic patients without/with VNT. Also, these levels were negatively correlated with platelet count in the combined group of cirrhotic patients without/with VNT. These findings may suggest that in cirrhotic liver with VNT and/or the risk of developing variceal bleeding, the increase in choline as a cellular biomarker reflects the continual destruction of functional hepatic tissue and hepatocytes, which could eventually result in hepatic failure.
In our study, when evaluating the effect of age, spleen diameter, platelet count, and ratio of platelet count/spleen diameter on metabolite alterations in cirrhotic patients with VNT, significant risk factors that were associated with altered hepatic metabolism and indicated the presence of VNT in cirrhotic liver included older age, longer spleen diameter, lower platelet count, and lower ratio of platelet count to spleen diameter. Meanwhile, when a cut-off value of 0.61 for lactate + TG and 0.09 for choline was used, the ROC analysis revealed 100% specificity for lactate + TG and 73% specificity for choline in differentiating cirrhotic patients with esophageal VNT from cirrhotic patients without VNT. This result suggests that 1H-MR spectroscopy could be effectively used to stratify cirrhotic patients in terms of the risk of esophageal variceal bleeding.
Our study has several limitations. First, we did not apply multi-voxel scanning when acquiring in vivo quantitative 1H-MRS because such a technique requires much longer scanning and breath-holding times. Second, the number of patients in our study was relatively small, therefore a larger number of patients in a prospective study may be necessary to verify our results. Third, as mentioned in the discussion, the lactate signal at 1.3 ppm could not be separated from the TG peak. Thus, utilizing high-field MRI equipment, spectrally overlapped lactate and TG signals at 1.3 ppm should be separated and quantified in future studies.