In the supine patient, free fluid from the right upper quadrant (RUQ) will tend to collect in Morison pouch first, whereas free fluid from the left upper quadrant (LUQ) will often accumulate in the left subphrenic space initially (i.e., not the splenorenal recess) The amount of intraperitoneal fluid needed for detection by ultrasound has been reported to be as little as 100 mL in adults and will depend on the source of the bleeding and patient positioning Technique Probe selection is the first step A low-frequency (2 to MHz) probe should be chosen for adequate penetration, most commonly a large footprint curvilinear probe In pediatric trauma, however, the smaller head of a phased array probe or microconvex probe may be more useful to obtain images between the small intercostal spaces There are four views of the FAST examination: (a) hepatorenal recess or Morison pouch, (b) splenorenal recess, (c) pelvic/bladder view, and (d) subxyphoid pericardial view (Fig 131.6 ) Many practitioners also incorporate views of the thorax to assess for hemothorax or pneumothorax, referred to as the enhanced FAST or eFAST The sonographer should perform the FAST examination in a systematic manner in a standard sequence This will allow greater focus on image acquisition and optimization as the examination order becomes routine A view of Morison pouch can be obtained by placing the probe in the coronal plane (marker toward the patient’s head) in the anterior axillary line between the seventh and ninth ribs on the patient’s right-hand side If rib shadows prevent optimal images, the probe can be rotated slightly in a counterclockwise fashion such that it is oriented in between and parallel to the ribs Once the hepatorenal recess comes into view, the probe can be moved or fanned superiorly toward the patient’s head and inferiorly toward the feet to visualize Morison pouch completely, as well as the inferior portions of the liver and kidney ( Video 131.2 ) As mentioned earlier, blood will tend to accumulate in these dependent portions of the peritoneal cavity initially ( Video 131.3 ) The splenorenal recess is often more difficult to view Because the left kidney sits more superior and posterior than the right kidney, starting position for the probe is the coronal plane (marker to the patient’s head) between the fifth and seventh ribs in the posterior axillary line on the left Rotation of the probe slightly should help avoid rib shadows In this view, blood will frequently accumulate between the spleen and diaphragm, so it is important to visualize the superior portion of the spleen in addition to the splenorenal junction ( Videos 131.4 [normal] and 131.5 [abnormal]) The pelvic view is obtained by placing the probe transversely (marker to the patient’s right), just above the symphysis pubis and angling the probe inferiorly toward the feet A full bladder will appear as a large anechoic structure and free fluid will be seen either posterior to or superior to the bladder wall For this reason, a sagittal view visualizing the superior bladder wall is always necessary for a complete examination ( Videos 131.6 [normal] and 131.7 [abnormal]) Finally, the subxiphoid view of the heart is obtained It is important to remember that the heart sits slightly rotated in the thorax, with the right ventricle most anterior and the left ventricle posterior and toward the patient’s left hip The transducer should lie almost parallel to the abdomen, just below the xiphoid process, with the marker toward the patient’s right-hand side and probe angled toward the left shoulder (Fig 131.6 ) The probe can be slid rightward along the inferior portion of the rib, using the liver as an acoustic window to avoid the artifacts caused by air in the stomach The normal pericardium is seen as a hyperechoic (bright) line surrounding the heart (Fig 131.7 ) Pericardial fluid will appear as an anechoic collection between the myocardium and bright pericardium ( Video 131.8 ) A more detailed description of bedside echocardiography is discussed in the next section FIGURE 131.6 Probe positions for the abdominal FAST scan (A) Morison pouch, (B) splenorenal recess, (C) pelvic, and (D) subcostal cardiac Pitfalls For the Morison pouch and splenorenal recess views, the most common difficulty arises from rib shadows The probe can be rotated about 20 degrees such that its orientation is parallel to the course of the ribs above and below The probe can also be moved either anterior or posterior to optimize images It is also important to recognize the inferior vena cava and the gallbladder in the RUQ scan Both of these structures typically appear anechoic and can mimic free fluid in Morison pouch for the inexperienced sonographer The splenorenal recess is more difficult to visualize than Morison pouch because of the relative superior position of the left kidney and smaller spleen size Often, the probe is not positioned posterior or cephalad enough A frequent pitfall with the pelvic view is the inability to visualize the bladder Sometimes the bladder is empty (i.e., when a Foley catheter has been placed) More often, the probe is positioned too superior and should be slid and/or angled toward the feet Less commonly, the bladder is off of midline to the right or left There are several reasons why a sonographer may not view the heart during the cardiac examination First, the depth has not been adjusted from the abdominal scans The abdominal organs lie relatively closer to the skin than the heart does to the subxiphoid process, and thus, the heart will often be deeper than the maximal depth set on the monitor By increasing the depth prior to the cardiac scan, the heart will come into view easily Second, the angle of the probe may be too steep Remember that from the subcostal position, the heart lies superiorly and the head of the transducer must be pointed in that direction Third, air from the stomach can scatter the ultrasound beams, rendering the image unreadable The probe should be slid to the patient’s right, away from the stomach, thereby using the liver as an acoustic window instead FIGURE 131.7 Normal subxiphoid cardiac view RV, right ventricle; LV, left ventricle; RA, right atrium; LA, left atrium Cardiac Cardiac ultrasound as part of the FAST examination was one of the first applications of POCUS Subsequently, there has been increasing use of cardiac examinations for nontraumatic conditions The basic questions asked when performing focused bedside echocardiography are (i) “Is the heart beating?” and (ii) “Is there a pericardial effusion?” Consequently, the two most common indications for bedside cardiac ultrasound are (i) evaluating for cardiac activity in patients with cardiac arrest or pulseless electrical activity (PEA) and (ii) assessing for pericardial effusions Although these scenarios are much less common than in