|
|
|
Trauma: The FAST Exam
Anywhere from 1-7 views
Use sector probe 2-3.5 MHz
Each view should take 30-60 seconds
Most sensitive view for free fluid in peritoneal space
Made more sensitive by scanning in Trendelenburg. 97% sensitivity c 1 L of
fluid, 10 % Sensitivity with 400 cc
Attempt the scan in sagittal at right midclavicular line moving the probe
laterally until kidney/liver interface comes into view. From this position, you
can see Morrison’s, check for pleural effusion (sensitivity increased with
patient flat or in reverse Trendelenburg,) examine paracolic gutters and the
liver parenchyma.
If you must scan RUQ in coronal, placing arms over head will open up
intercostals spaces. Scan in oblique just off coronal with probe on mid-ax line
and indicator pointing towards post-ax line
Blood/fluid collections have sharp edges and points b/c it will fill the space
between structures. Blood is anechoic, but if there are clots, will be
hypoechoic.
Liver level signals should be seen on both sides of the diaphragm, if there is
an anechoic area opposite liver tissue, it is pleural fluid.
RUQ mean volume required to detect fluid in a dialysis
model was 619 cc, at 1 liter, sensitivity was 97%)
Subxiphoid scan c overhand grip. 20-30° off of abdomen
aiming at left midclavicular line in transverse orientation with the indicator
to patient’s right (The surgeons do it in sag for some reason). The liver and
right ventricle (wedge shaped) will be the first structures seen. They should be
in close contact. Anterior fat pad can give false positive, so best if fluid can
be seen posterior to left ventricle as well.
Rozycki Study (J Trauma 1999;46(4):543)
Higher than right kidney. Mid axillary line with probe
aimed at posterior axillary line. Find kidney then move up until spleen
interface is seen. Examine potential splenorenal space for fluid. Scan paracolic
gutter, look above diaphragm for pleural effusion, and examine spleen parenchyma
for obvious injury (intraparenchymal blood is echogenic), or subdiaphragmatic
blood.
false positive:
gastric
bubble
The most inferior part of the peritoneal cavity is the
pouch of Douglas (cul-de-sac) in women or the Retrovesicular pouch in men.
Bladder is the acoustic window, so makes life easier if the FAST is done before
foley placement. The bladder will cause acoustic enhancement directly behind it
so adjust gain accordingly. First do sagittal to locate bladder and determine
level (you must be above prostate or vagina), then turn transverse to evaluate
fluid.
Women: blood may be seen anterior or posterior to the uterus
Men: do not be confused by prostate or seminal vesicles. Look for bowtie sign,
fluid on either side of bladder as this is the easiest part for blood to fill.
· Identification of portal vein or IVC as free fluid
· Seminal vesicles as free fluid
· Perinephric fat can appear hypoechoic
· Anterior fat pad of heart can appear hypoechoic (almost always located
anterior to the R ventricle and not behind L ventricle)
· Not going posterior enough or high enough on LUQ exam, fingers should touch
table
· Mistaking ascites for blood. Examine liver for signs of cirrhosis (increased
echogenicity, thickened GB wall, splenomegaly)
RUQ:
Preferably Sagittal showing post. Pleural space, diaphragm, liver, kidney, and
Morrison’s pouch
LUQ:
Coronal showing spleen, kidney, diaphragm, posterior pleural space, splenorenal
interface
Cardiac:
Pericardium, preferably with posterior as well as anterior
Suprapubic:
Transverse of bladder showing pouch of Douglas or Retrovesicular space. Must be
above the level of the prostate or vagina
Include in documentation limited or incomplete study, Dx (Definite, Probable,
Possible, Uncertain), and confirmatory study.
| Study | Study Class | Study Size | No. of Patients With Hemoperitoneum | Sensitivity, % | Specificity, % | Positive Likelihood Ratio | Negative Likelihood Ratio |
| Ma et al 21 | I | 245 patients | 64 | 90 | 99 | 90 | 0.1 |
| Rozycki et al22 | II | 1,227 patients | 96 | 83.3 | 99.7 | 278 | 0.17 |
| Shackford et al23 | I | 241 patients | 51 | 68 | 98 | 34 | 0.33 |
| Smith et al24 | III | 841 patients | 45 | 73 | 98 | 36.5 | 0.28 |
| Tso et al10 | II | 163 patients | 11 | 91 |  |
(Annals 2004, 43:2 Policy on Blunt Abd Trauma)
Radiology. 2003 Dec;229(3):766-74. Related Articles, Links
Screening US for blunt abdominal trauma: objective predictors of false-negative
findings and missed injuries.
Hematuria and fracture of the lower ribs, lumbar spine, or pelvis are objective
predictors of missed abdominal injury in patients with blunt abdominal trauma
and negative US findings, and such patients may benefit from additional
screening with computed tomography.
consider cut of of 8 mm for IVCe diameter (expiratory)
(American JEM 2005;23:45)
100% sensitivity for FAST in pts with hypotension
Rozycki GS, Ballard RB, Feliciano DV, Schmidt JA, Pennington
SD. Related Articles, Links
Surgeon-performed ultrasound for the assessment of truncal injuries: lessons
learned from 1540 patients.
Ann Surg. 1998 Oct;228(4):557-67.
Sens 97% in radiology study for injuries requiring surgery (Radiology 2005;235:436)
Home | Disclaimer | Contact | Podcast