This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Trauma, Subject name: Surgery
False about eFAST 
Select and explain. 
A. Detects free fluid in the abdomen or pericardium, B. Will not reliably detect less than 100 mL of free blood, C. Can reliably exclude injury in penetrating trauma, D. Unreliable for assessment of the retroperitoneum
C: Can reliably exclude injury in penetrating trauma
Answer: C: Can reliably exclude injury in penetrating trauma 
Explanation: Extended focused assessmentwith sonar for trauma (eFAST) is becoming the mostcommon investigation. The technique uses sonar assessmentin the chest, looking for a cardiac tamponade or free bloodand air in the hemithorax on each side, and assessment forblood in the abdominal cavity, in the paracolic gutters,subdiaphragmaticspaces and pelvis.Detects free fluid in the abdomen or pericardiumWill not reliably detect less than 100 mL of free bloodDoes not directly identify injury to hollow viscusCannot reliably exclude injury in penetrating traumaMay need repeating or supplementing with other investigationsIs unreliable for assessment of the retro-peritoneumBailey and love 27e pg: 372