FAST Examination

FAST is a focused, goal-directed ultrasound scan for the abdomen and pericardium in order to detect existence of blood in these cavities. It is part of the primary survey for patient with evidence of abdominal/truncal injury and suspicion of haemorrhage(profuse bleeding from ruptured blood vessels). Demonstration had show FAST has a sensitivity of haemorrhage of 86% to 99% and a specificity of 90% to 99%. FAST is recommended to be performed using a 3.5 or 5 MHz ultrasound sector transducer probe and gray scale ‘B mode’ ultrasound scanning. The total time taken for a scan would be around 5-8 minutes.

A FAST examination consists of 4 scans.

Perihepatic Scanning (RUQ)
The hepatorenal space (pouch of Rutherford-Morison) is the most dependent part of the upper peritoneal cavity and small amounts of intra-peritoneal fluid may collect in this region first. 80% of haemoparitonium  could be detected with heptorenal view alone. Planning beams in this plan demonstrate liver, kidney and diaphragm. Look for blood in the RUQ and fluid between liver and kidney.
The probe is placed in the right mid- to posterior axillary line at the level of the 11th and 12th ribs.
Perisplenic Scanning (LUQ)
The left upper quadrant examination visualises the spleen and perisplenic areas.Planning beams in this plane demonstrate spleen, kidney and diaphragm. Look for blood between spleen and kidney or diaphragm.The transducer is placed on the left posterior axillary line region between the 10th and 11th ribs.
Pelvic Scanning
The pelvic examination visualises the cul-de-sac: the Pouch of Douglas in females and the rectovesical pouch in the male. It is the most dependent portion of the lower abdomen and pelvis, hence where fluid will collect.
The transducer is placed midline just superior to the symphysis pubis, angled downwards. It is then rotated 90 degrees to move beam into sagittal plane.
Pericardial Scanning
The pericardial examination screens for fluid between the fibrous pericardium and the heart, and hence possible cardiac tamponade.
The transducer is placed just to the left of the xiphisternum and angled upwards under the costal margin.

Referenced from:

Focused Abdominal Sonography in Trauma (FAST)

Col R Chaudhry, VSM*, Lt Col A Galagali+, Maj RV Narayanan#