Pelvic fractures, while primarily diagnosed by CT or X-ray, can have indirect findings on a FAST (Focused Assessment with Sonography for Trauma) exam. In the context of trauma ultrasound, the primary utility of FAST is to rapidly detect free fluid, such as blood, in the peritoneal cavity, which may be associated with pelvic bleeding. While ultrasound cannot directly visualize bone fractures, the presence of significant free fluid in the pelvic views (suprapubic or retrovesical spaces) of the FAST exam in a trauma patient with suspected pelvic injury should raise concern for hemorrhage.
Ultrasound may also show a pelvic hematoma, appearing as an ill-defined, heterogeneous collection of fluid. Therefore, while not definitive for bone injury, ultrasound plays a crucial role in the initial assessment of hemodynamic stability by identifying intrapelvic hemorrhage in trauma patients.