Focused Assessment with Sonogram in Trauma

Trauma: The FAST Exam
Anywhere from 1-7 views

Use sector probe 2-3.5 MHz

Each view should take 30-60 seconds

RUQ

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%)

Cardiac

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)

LUQ

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

Pelvis

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.

Pitfalls

· 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.

IVC

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)