MDCT evaluation of blunt abdominal trauma: clinical significance of free intraperitoneal fluid in males with absence of identifiable injury.

Objective: The purpose of our study was to determine the clinical significance of the isolated finding of free intraperitoneal fluid on 64-MDCT in male patients who have undergone blunt trauma.

Materials And Methods: A retrospective study was performed of 669 consecutive male patients, ranging in age from 15 to 85 years, who underwent CT evaluation of the abdomen and pelvis at our level 1 trauma center over a 17-month period. Two radiologists evaluated the images for the presence of free intraperitoneal fluid and for an underlying cause. For patients with free intraperitoneal fluid, the mean attenuation and the size of the largest pocket of fluid on both portal venous and delayed phase images were measured for both those with and those without injury. For the patients who had free intraperitoneal fluid as an isolated finding, the electronic chart was reviewed to determine the clinical outcome, specifically whether these patients were observed, had short-interval follow-up imaging, or underwent exploratory laparotomy.

Results: Forty-eight of the 669 patients (7.2%) had free intraperitoneal fluid. Twenty-nine (4.3%) of these patients had an identifiable solid organ, bowel, bladder, or pelvic injury to explain the free fluid. In the remaining 19 (2.8%) patients, free fluid was an isolated finding. The size of the largest collection of fluid was smaller for patients without identifiable injury on portal venous phase (1,236 vs 348 mm(2)) and delayed phase (1,325 vs 298 mm(2)) images (p = 0.0015 and p < 0.0001, respectively). Fluid in patients without identifiable injury was also shown to be less dense. A statistically significant difference between the mean attenuation coefficients of the fluid in the patients with and without injury was also found on both the portal venous phase (45.1 vs 13.1 HU, p < 0.0001) and delayed phase (45.6 vs 20.8 HU, p < 0.0001) images. All 19 patients without identifiable injury were admitted for observation and discharged without surgical intervention.

Conclusion: With 64 MDCT, the isolated finding of free intraperitoneal fluid in male patients who have undergone blunt trauma is seen in approximately 3% of patients. The size and mean attenuation coefficient measurements may add useful information regarding the clinical management of these patients, suggesting that small amounts of low-attenuation free fluid, in the absence of identifiable injury, may have no significant clinical implications.