The presented invention provides a detection method for free fluid in the human body. The preprocessing procedure is applied to reduce the speckle noise and enhance tissue volumetric pixels (voxels) intensity levels to make tissue and non-tissue voxels more distinguishable from each other. An initial surface selection step provides flexibility to either manually or automatically selecting a seed point to segment fluid regions in the volumetric data. A kidney and liver organ detection procedure provides a method for determining whether the detected fluid region is a normal fluid-carrying body organ or if it is due to a medical condition as a free fluid region. A combinational approach using a 3-dimensional Snake and Level-Set is utilized to accurately detect fluid regions in the volumetric ultrasound data.