Background: Rapid ultrasound in shock (RUSH) is the most recent emergency ultrasound protocol, designed to help clinicians better recognize distinctive shock etiologies in a shorter time frame. Objectives: In this study, we evaluated the accuracy of the RUSH protocol, performed by an emergency physician or radiologist, in predicting the type of shock in critical patients. Patients and Methods: An emergency physician or radiologist performed the RUSH protocol for all patients with shock status at the emergency department. All patients were closely followed to determine their final clinical diagnosis. The agreement between the initial impression provided by RUSH and the final diagnosis was investigated by calculating the Kappa index. Sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of RUSH for diagnosis of each case. Results: We performed RUSH on 77 patients. Kappa index was 0.71 (P Value = 0.000), reflecting acceptable general agreement between initial impression and final diagnosis. For hypovolemic, cardiogenic and obstructive shock, the protocol had an NPV above 97% yet it had a lower PPV. For shock with distributive or mixed etiology, RUSH showed a PPV of 100% but it had low sensitivity. Subgroup analysis showed a similar Kappa index for the emergency physician and radiologist (0.70 and 0.73, respectively) in performing rush. Conclusions: This study highlights the role of the RUSH exam performed by an emergency physician, to make a rapid and reliable diagnosis of shock etiology, especially in order to rule out obstructive, cardiogenic and hypovolemic shock types in initial exam of shock patients.