1. Home>
2. Specialties>
3. Emergency Medicine>
4. Summary and Comment

FAST Is Less Accurate in the Presence of Major Pelvic Fracture

Uroperitoneum is responsible for almost 20% of true positives.

Anatomic distortion caused by pelvic fracture displacement and hematoma formation may lessen the accuracy of hemoperitoneum detection by four-quadrant focused assessment with sonography in trauma (FAST). Researchers tested this hypothesis in a retrospective cohort of 87 blunt trauma patients (mean age, 42 years; 55% men) who presented to a single trauma center with any one of four major pelvic fracture Tile subtypes: A2, direct injury to innominate bone or anterior pelvic arch (9%); B, rotational unstable pelvic injury (72%); C, completely unstable pelvic ring injuries (16%); and C, acetabular fractures and associated bone column acetabular fractures (3%). All FAST exams were conducted by emergency physicians or surgeons, and the results were compared against those of abdominopelvic computed tomography (CT), diagnostic peritoneal tap, or exploratory laparotomy.

The overall sensitivity of FAST for detection of free peritoneal fluid was 80.8%, with a specificity of 86.9%, a positive predictive value of 72.4%, and a negative predictive value of 91.4%. Sensitivity and specificity, respectively, ranged from 73% to 75% and 75% to 85% for A2 and B fractures but were each 100% for C fractures. Eight false-positive results included extensive pelvic hematoma, extraperitoneal bladder rupture, and no fluid seen on CT. Five false-negative results included splenic laceration, liver laceration, and hemoperitoneum of unknown source; in each case, small collections of free peritoneal fluid were present on CT. Of the 21 true-positive results, 4 (19%) were caused by urine from intraperitoneal bladder rupture. One of the patients with uroperitoneum was hemodynamically unstable and underwent emergent laparotomy for the nonemergent indication of bladder rupture, followed by diagnostic and therapeutic pelvic angiography.

Comment: Patients with major pelvic fractures are frequently hemodynamically unstable, and the primary purpose of FAST is to rapidly formulate the next critical step. If FAST is negative, that step is angiography to localize and staunch retroperitoneal hemorrhage. If FAST is positive, these authors advise performing a supraumbilical diagnostic peritoneal tap. If blood is aspirated, laparotomy is indicated; if urine is aspirated, then pelvic angiography should precede laparotomy.

— John A. Marx, MD, FAAEM, FACEP

Published in Journal Watch Emergency Medicine February 9, 2007

Citation(s):

Tayal VS et al. Accuracy of trauma ultrasound in major pelvic injury. J Trauma 2006 Dec; 61:1453-7.

• Medline abstract (Free)

2011 Top Stories