Basic scan in patients with trauma, abdominal or thoracic pain, or unexplained hypotension. The caudal edge of the liver in the right upper quadrant is the most sensitive position to identify even small amounts of pathologic peritoneal fluid. Findings of free fluid in the abdomen can suggest blood from trauma or ectopic rupture, ascites from any cause, or in rare cases bowel contents. The probe can easily slide up to screen for pleural effusions and/or hemothroax by crossing the diaphragm after scanning the abdomen.