Background and objective We aimed to determine the diameters and respiratory variability of the subclavian vein (SCV), internal jugular vein (IJV), and femoral vein (FV), which are more superficial and easier to visualize with point-of-care ultrasound (PoCUS) in the detection of volume overload, and to investigate whether they can be an alternative to analyzing an inferior vena cava (IVC) to determine volume load. Methodology We prospectively evaluated volume-overloaded and normovolemic patients admitted to the emergency department using PoCUS for six months. Inspiratory-expiratory diameters and collapsibility indices (CI) of IVC and SCV, IJV, and FV were evaluated. The correlation between IVC and SCV, IJV, and FV was analyzed. Results A total of 176 patients were included in the study, including 88 volume-overloaded patients in the study group and 88 normovolemic patients in the control group. The median values of the maximum and minimum diameters of the IVC, SCV, IJV, and FV in the study group were statistically higher compared to the control group. A moderate correlation was found between IVC and SCV, IVC and IJV, and IVC and FV for maximum diameters in all patients (p = 0.447, p = 0.515, and p = 450, respectively). There was a very weak correlation between the IVC-CI and the FV-CI in all patients (p = 0.160), and no correlation was found with the other veins. Conclusion The IVC-CI was not correlated with the SCV-CI, the IJV-CI, or the FV-CI in volume-overloaded patients
therefore, superficial venous vessels cannot be an alternative to the IVC.