"The small amount of isolated pelvic free fluid were identified at or below the level of the third sacral vertebral body in all 49 patients; no patients in this group had an undiagnosed bowel and/or meseneteric injury."

Frequency and Importance of Small Amount of Isolated Pelvic Free Fluid Detected with Multidetector CT in Male Patients with Blunt Trauma
Yu J et al
Radiology 2010; 256:799-805

"The mean volume and the mean attenuation of the pelvic free fluid in 13 patients who had surgically proved bowel and/or mesenteric injury were 41.5 ml ± 12.4 and 34.8 HU ± 10.7 respectively."

Frequency and Importance of Small Amount of Isolated Pelvic Free Fluid Detected with Multidetector CT in Male Patients with Blunt Trauma
Yu J et al
Radiology 2010; 256:799-805

"In male patients with blunt trauma, a small amount of isolated pelvic free fluid with attenuation equal to that of simple fluid and located in the deep region of the pelvis likely is not a sign of bowel and/or mesenteric injury."

Frequency and Importance of Small Amount of Isolated Pelvic Free Fluid Detected with Multidetector CT in Male Patients with Blunt Trauma
Yu J et al
Radiology 2010; 256:799-805