The FAST (Focused Assessment with Sonography for Trauma) exam is a standardized rapid ultrasound protocol used in trauma resuscitation to detect free intraperitoneal fluid (hemoperitoneum) and pericardial effusion. Four windows are assessed: right upper quadrant (Morrison’s pouch), left upper quadrant (splenorenal space), suprapubic (pelvis), and subxiphoid (pericardium). The extended FAST (eFAST) adds bilateral lung and pleural views to detect pneumothorax and hemothorax. A positive FAST in an unstable trauma patient may prompt immediate surgical intervention.