OBJECTIVE: This study is designed as prospective and observational research of patients with sepsis. It was carried out in the intensive care unit (ICU). We investigated the shape change index (SCI) of inferior vena cava (IVC) measured with trans-abdominal ultrasound to detect the signs of septic shock. The aim of this research was to find the most effective tool in predicting shock in patients compared with that of other parameters such as brain natriuretic peptide (BNP), lactate, variation index of inferior vena cava IVC-VI, and extravascular lung water index (EVLWI). PATIENTS AND METHODS: We suppose that SCI can be used as the safest and most sensitive tool in the early recognition of septic dysfunction. The observational study was conducted in the Department of ICU, Shandong Provincial Hospital Affiliated to Shandong University from January 2016 to December 2017. SCI of IVC, serum lactate, BNP, IVC-VI, and EVLWI concentrations were measured in 30 sepsis patients. All studied biomarkers were analyzed and contrasted according to the score of the Sequential Organ Failure Assessment (SOFA). Pearson correlation analysis was analyzed to statistic the relationship between variables. RESULTS: We showed the correlation of BNP value, lactic acid value, IVC-VI, EVLWI, and SCI of IVC in sick patients suffering septic shock. Positive correlation was observed in the BNP value, lactic acid value, IVC-VI, EVLWI, and SCI of IVC (r=0.447, p=0.013; r=0.484, p=0.007; r=0.423, p=0.023; r=0.638, p<0.001; r=0.599, p<0.001; respectively). However, the SCI and EVLWI showed a stronger correlation with the SOFA than the others. SCI of IVC, as estimated by transabdominal ultrasound, was more accurate than the other commonly used non-invasive predictors. EVLWI, as an accurate and classical predictor, was an invasive predictor. SCI of IVC was faster, more convenient and safer than the other. CONCLUSIONS: SCI of IVC was faster, more convenient and safer than the other commonly used non-invasive predictors. Early recognition and diagnosis of sepsis may improve patient outcome.