Diagnostic Accuracy of eFAST in the Trauma Patient: A systematic Review and Meta-Analysis
The objective of this study was to systematically review the published literature on diagnostic accuracy of all components of the eFAST exam.
767 records remained for screening, of which 119 underwent full text review.
75 studies representing 24,350 patients satisfied our selection criteria.
Pooled sensitivities and specificities were calculated for the detection of pneumothorax (69% and 99% respectively), pericardial effusion (91% and 94% respectively), and intra-abdominal free fluid (74% and 98% respectively). Sub-group analysis was completed for detection of intra-abdominal free fluid in hypotensive (sensitivity 74% and specificity 95%), adult normotensive (sensitivity 76% and specificity 98%) and pediatric patients (sensitivity 71% and specificity 95%).
This systematic review and meta-analysis suggests that e-FAST is a useful bedside tool for ruling in pneumothorax, pericardial effusion, and intra-abdominal free fluid in the trauma setting (high specificity, not high sensitivity)
Netherton S, Milenkovic V, Taylor M, Davis PJ. Diagnostic accuracy of eFAST in the trauma patient: a systematic review and meta-analysis. CJEM. 2019 Nov;21(6):727-738. PMID: 31317856.
Sensitivity in Detecting Free Intraperitoneal Fluid with the Pelvic Views of the FAST Exam
In this prospective observational study, von Kuenssberg, et al. aimed to determine the average minimal volume of intraperitoneal fluid required for detection in the suprapubic view of the FAST exam. Seven patients who met inclusion criteria of blunt abdominal trauma and clinically indicated diagnostic peritoneal lavage underwent Foley catheter placement and sequential instillation of 100 mL aliquots of lavage fluid followed by transverse and longitudinal pelvic ultrasound until examiner visualized free pelvic fluid. Hard copy images of ultrasounds were produced at time of evaluation for evaluation by a blinded reviewer. Patients were excluded if initial multiview FAST examination demonstrated free fluid, DPL was positive for hemoperitoneum, or insufficient hard copy images were obtained. Mean minimal volume required for free pelvic fluid visualization were 157 mL and 129 mL by examiner and reviewer respectively. Median minimal volume was determined to be 100 mL for both examiner and reviewer.
Although limited by small sample size, this study adds to existing literature threshold volumes of free fluid required to determine a positive examination in the pelvic view of the FAST exam. Of note, this threshold is below the volumes previously determined for a positive examination in the perihepatic view. While lower fluid volumes may be detectable in the pelvic view, these findings do not alter the order of evaluation of the multiview FAST examination in the setting of blunt abdominal trauma as Morison’s Pouch visualized in the perihepatic window remains the most dependent site for free fluid collection within a supine patient.
Von Kuenssberg Jehle D, Stiller G, Wagner D. Sensitivity in detecting free intraperitoneal fluid with the pelvic views of the FAST exam. Am J Emerg Med. 2003 Oct;21(6):476-8. doi: 10.1016/s0735-6757(03)00162-1. PMID: 14574655.
Focused Assessment with Sonography for Trauma Examination: Reexamining the Importance of the Left Upper Quadrant View
In this retrospective review, Adhikari et al. examine the frequency and predominant location of isolated free fluid within the left upper quadrant view on FAST examination. Ultrasonographic images of patients aged 18 and older with a positive FAST examination were included. Images were excluded if chart review yielded a history of ascites, peritoneal dialysis, or FAST exam preformed for reason other than blunt or penetrating trauma. Images were selected by querying physician work sheets and quality assessment sheets. Image quality was assessed by both a study investigator and a blinded emergency sonologist reviewer. Images were deemed adequate if negative for left upper quadrant fluid and had full visualization of subphrenic space, splenorenal recess, and left paracolic gutter. Images positive for left upper free fluid were deemed adequate regardless of visualization of all three spaces. Of the 405 FAST exams preformed, 100 met inclusion criteria. Of the included images, 32 were positive for free fluid in the left upper quadrant, of which six were found to have left upper quadrant isolated free fluid. The left paracolic gutter was the most common place of isolated free fluid followed by the subphrenic space. No instances of isolated free fluid within the splenorenal recess were found. Of the included examinations, 41% were deemed inadequate on image review with the predominant reason being inadequate visualization of the subphrenic space. The findings of isolated left upper quadrant free fluid most commonly in the left paracolic gutter contradicts conventional teaching of the free fluid accumulating in the subphrenic space and overflowing into the splenorenal recess and then the left paracolic gutter. Given these findings, ultrasound education should emphasize full examination of the left upper quadrant and in particular the left paracolic gutter.
O’Brien KM, Stolz LA, Amini R, Gross A, Stolz U, Adhikari S. Focused Assessment With Sonography for Trauma Examination: Reexamining the Importance of the Left Upper Quadrant View. J Ultrasound Med. 2015 Aug;34(8):1429-34. doi: 10.7863/ultra.34.8.1429. PMID: 26206829.
Caudal Edge of the Liver in the Right Upper Quadrant (RUQ) View is the most Sensitive Area for Free Fluid on the FAST Exam
In this single center retrospective review, Gharahbaghian et al. reviewed recorded positive FAST exams to evaluate for the most sensitive intraperitoneal area of free fluid accumulation. Positive studies were assessed for free fluid accumulation in the traditional four quadrant FAST exam views with subcategorization of each quadrant [RUQ1, 2, 3 – hepatodiaphragmatic, Morison’s Pouch, caudal liver edge; LUQ1, 2, 3 – splenic diaphragmatic, splenorenal, inferior pole of left kidney; SP1, 2, 3 – bilateral to bladder, posterior to bladder, posterior to uterus (females only)]. Study included all adult trauma patients with recorded FAST examinations. Images were excluded for incomplete visualization of all three quadrants, poor image quality such that subquadrants were not assessable, incomplete medical record information for review of CT or operative findings. A total of 1,158 images were obtained, of which 12.9% were excluded. Of the 1,008 included images, 4.8% (48) were positive for free fluid. To calculate test characteristics, ultrasound imaging findings were compared to CT imaging or operative report findings. Of the traditional intraperitoneal FAST views, the right upper quadrant was most commonly positive (32/48), followed by the suprapubic (23/48) and left upper quadrant (17/48). Among the subquadrants, RUQ3 was most commonly positive (30/32) followed by RUQ2 and RUQ1 views. Of the left upper quadrant and suprapubic subquadrant analyzes, LUQ1 and SP1 were most sensitive. Of note, the RUQ1 and LUQ3 quadrants do not perform better than chance; whereas, all other subquadrants predict their outcome with statistical significance. While this study is limited by design constraints including retrospective analysis and time lag between ultrasonic evaluation and criterion imaging or surgical evaluation, it provides sufficient evidence that right upper quadrant view in the fast examination is the most sensitive region and that the caudal edge of the liver is the most sensitive site within the right upper quadrant for detection of free fluid.
Lobo V, Hunter-Behrend M, Cullnan E, Higbee R, Phillips C, Williams S, Perera P, Gharahbaghian L. Caudal Edge of the Liver in the Right Upper Quadrant (RUQ) View Is the Most Sensitive Area for Free Fluid on the FAST Exam. West J Emerg Med. 2017 Feb;18(2):270-280. doi: 10.5811/westjem.2016.11.30435. Epub 2017 Jan 19. PMID: 28210364; PMCID: PMC5305137.
Emergency Physician Use of Ultrasonography in Blunt Abdominal Trauma
In this prospective observational study, Knotts et al. evaluated the utility of emergency physician preformed diagnostic ultrasound for intraperitoneal free fluid of patients presenting for evaluation following blunt abdominal trauma. Emergency attendings and residents underwent a two hour training course with one hour of didactic learning and one hour live scanning prior to study initiation. Patients were selected on a convenience sampling based on availability of study provider. Patients of any age who presented for evaluation of blunt abdominal trauma and were deemed by trauma surgeon to require further evaluation with abdominal CT, diagnostic peritoneal lavage, or laparotomy were included. Cases without criterion reference, insufficient documentation, and those lacking medical records were excluded. FAST examination consisted of ultrasonographic imaging of hepatorenal space, suprapubic space, and splenorenal recess. Real time hard copy images were produced for review by radiologist who was blinded to patient outcomes. Additionally, the trauma surgeon was blinded to the ultrasound findings at time of examination. Secondary outcomes assessed time to image acquisition and test characteristics between pediatric and adult populations.
Of the 110 enrolled patients, 13 were excluded for either poor image quality, technical difficulties with the ultrasound machine, or no available hospital records. Of the 97 remaining patients, 66 were adults and 31 pediatrics (age less than or equal to 18). Point-of-care ultrasound revealed 21 total positive case (18 true positives, 3 false positives) and 76 negatives (70 true negative, 6 false negatives) for test characteristics of 75% sensitivity, 96% specificity, 86% positive predictive value, and 92% negative predictive value. Of the criterion testing, 24 true positive were found, all of whom underwent laparotomy either directly after ultrasound or following CT or DPL. Notably, not all three FAST views were obtained in every patient. Heptaorenal view was obtained in 100% of patients, followed by splenorenal recess in 89% and suprapubic in 73% of patients. Mean time for obtaining ultrasound images was 4.9 +/- 2.9 mins. Time constraints in scanning hemodynamically unstable patient and prior positive region cited as most common reasons for not obtaining all views. Blinded radiology reviewer reported more indeterminate images from splenorenal recess and suprapubic views than from hepatorenal recess. Additioanlly, hepatorenal view had the highest sensitivity for intraperitoneal free fluid as compared to remaining views; however, overall sensitivity of study increased with multiple views. No difference in sensitivities or specificities were determined between emergency medicine attending or resident obtained images. And, no difference in test characteristics observed between age groups.
While limited by high percentage of indeterminate scans (18%) as assessed by radiology reviewer and significant percent of enrolled patients not having all three intraperitoneal FAST views assessed (35%), this landmark paper provides sufficient evidence that timely ultrasonographic images can be obtained by emergency trained physicians on patients presenting with blunt abdominal trauma. Furthermore, these images should be used to guide trauma evaluation based on hemodynamic stability.
Ingeman JE, Plewa MC, Okasinski RE, King RW, Knotts FB. Emergency physician use of ultrasonography in blunt abdominal trauma. Acad Emerg Med. 1996 Oct;3(10):931-7. doi: 10.1111/j.1553-2712.1996.tb03322.x. PMID: 8891039.
Does This Adult Patient Have a Blunt Intra-abdominal Injury?
In this systematic review, Holmes et al. assess the precision and accuracy of clinical signs, laboratory testing, and bedside imaging in identification of intra-abdominal injuries secondary to blunt abdominal trauma. A structured search of MEDLINE and EMBASE databanks was conducted to find English-language studies. Of 2,704 studies meeting search criteria, 12 studies assessing clinical signs and symptoms of intra-abdominal injury secondary to blunt abdominal trauma were selected. An additional query was performed for diagnostic accuracy of bedside ultrasound returning 22 articles for review. All evidence was of grade one or two.
Prevalence of intra-abdominal injury in adult emergency department patients was determined to be 13%, representing pretest probability. Among historical findings and clinical signs, presence of ecchymosis across lower abdomen or a “seat belt” sign provides highest evidence for underlying injury (LR 5.6-9.9). While infrequently present, rebound tenderness should also raise clinical suspicion (LR 6.5). Abdominal distension and abdominal guarding were more often present and provide moderate evidence for injury (LR 3.8 and 3.7); whereas, reported abdominal pain and abdominal pain on palpation are less predictive of underlying injury (LRs 1.6 and 1.4).
Among commonly acquired laboratory testing in setting of trauma, base deficit of < -6 mEq/mL is highly predictive of intra-abdominal injury (LR 18). Hematuria as defined by >25 to 50 RBCs per high powered field, elevated trasaminases, and anemia with hematocrit levels < 30% carry moderate predictive values for underlying injury (LR 3.7-4.1, LR 2.5-5.2, and LR 3.3 respectively). In contrast, less severe anemia (Hct < 36%), elevated WBC count, and elevated lactate levels are less demonstrative of underlying pathology (LRs 2.2, 1.7, 1.3). An abnormal chest radiograph increases likelihood of concomitant intra-abdominal findings; however, a normal chest radiograph does not sufficiently rule out intra-abdominal injury (LR 2.5-3.8 and LR 0.7-0.96).
The FAST examination is the single most accurate bedside test for intra-abdominal injury in the setting of blunt abdominal trauma with likelihood ratios ranging from 30 to 82 based on factors including hemodynamic stability of patient, statistical heterogeneity, and possible publication bias. Given this high clinical probability, a positive FAST exam may outperform physician clinical judgement and essentially confirms intra-abdominal injury in cases with high clinical suspicion. However, a negative FAST exam in cases of low clinical suspicion is not sufficient to rule out intra-abdominal injury. Implementing routine FAST examination into trauma protocols has been shown to safely reduce frequency of abdominal CTs. A caveat to this is underestimation of false negative FAST examination can results in less accuracy of overall test. Overall, combinations of historical, physical exam, lab, and bedside imaging findings should be utilized to best evaluate for intra-abdominal injury in evaluation of patients for blunt abdominal trauma.
Nishijima DK, Simel DL, Wisner DH, Holmes JF. Does this adult patient have a blunt intra-abdominal injury? JAMA. 2012 Apr 11;307(14):1517-27. doi: 10.1001/jama.2012.422. PMID: 22496266; PMCID: PMC4966670.
Utility of Cardiac Component of FAST in Blunt Trauma
Retrospective chart review of two institutional databases at a Level I trauma center
Of 29,236 blunt trauma patients over an 8.5 year period, 18 (0.06%) had hemopericardium and cardiac rupture (14 and 4, respectively).
The prevalence of incidental or insignificant effusions was 0.13% (95% CI 0.09-0.18%). One case of blunt hemopericardium was identified in the emergency ultrasound database out of 777 cardiac ultrasounds over a 3-year period. No patient with blunt hemopericardium or cardiac rupture presented without a major mechanism of injury, hypotension, or emergent intubation.
Blunt hemopericardium is rare. High-acuity variables may help guide the selective use of echocardiography in blunt trauma.
Press GM, Miller S. Utility of the cardiac component of FAST in blunt trauma. J Emerg Med. 2013 Jan;44(1):9-16. doi: 10.1016/j.jemermed.2012.03.027. Epub 2012 Jul 4. PMID: 22766409.