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Free Fluid on MDCT in Males With Blunt Abdominal Trauma May Not Be Clinically Significant

October 1, 2009
Written by: , Filed in: Emergency Radiology
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A recent study was conducted in order to determine if the isolated finding of free intraperitoneal fluid on 64-slice multi-detector CT (MDCT) in male patients after blunt abdominal trauma is clinically significant.

The results, presented in a recent issue of AJR, are of interest in reference to abdominal imaging, since it concludes that the isolated finding of low-attenuation free intraperitoneal fluid in male patients without identifiable injury may not be clinically significant.

The Study

669 male patients underwent CT evaluation after sustaining blunt abdominal  trauma. Patients who had undergone penetrating abdominal injury were excluded.

All examinations were performed with a 64-slice MDCT scanner. Portal venous phase images were acquired after a 70-second scan delay.

If there was an abdominal injury suspected on the portal venous phase images, a 5-minute delayed-phase scan was also obtained.

Images were reviewed by 2 radiologists for presence of free intraperitoneal fluid in the abdomen.

If free fluid was seen, reviewers determined if there was a traumatic or nontraumatic cause for the fluid. Traumatic causes included solid organ injury, bowel or mesenteric injury, or pelvic injuries.

Nontraumatic causes for free fluid included cirrhosis or portal hypertension and cardiac failure.

The 2 largest perpendicular dimensions for the largest pocket of fluid, as well as its mean attenuation measurement in Hounsfield units (HU), were recorded.

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Results of the Study
Free intraperitoneal fluid was found in 48 of 669 patients. 29 of these 48 had at least 1 identifiable cause for the free fluid, which included injuries of the liver, spleen, bowel, mesentery, pancreas, or pelvic osseous structures.

Patients with and without an identifiable cause of injury were aged 15 to 86 years and 15 to 88 years, respectively.

All 19 patients without an identifiable source for intraperitoneal free fluid were admitted either for observation or treatment of other injuries, which included closed head injury, pneumothorax, and orthopedic injuries.

The size of the largest pocket of fluid was smaller for patients without identifiable cause of injury. Intraperitoneal fluid in patients without an identifiable injury was less dense, with a mean attenuation of 13 HU on portal venous phase images and 21 HU on delayed-phase images.

In those patients with an identifiable cause for free fluid, the mean attenuation of the fluid was 45 HU on portal venous phase images and 46 HU on delayed-phase images.

Reviewer’s Comments
The results of this study are useful in demonstrating that isolated free intraperitoneal fluid can be found in approximately 3% of male patients without an identifiable source who have undergone blunt trauma. Consequently, this fluid may have no clinical significance.

However, there was a statistically significant difference in the attenuation value of free fluid found in patients with an identifiable cause of injury as compared to those without a cause.

One of the limitations reported in this study was the lack of a reference standard such as surgical confirmation that there was no injury present in patients with isolated free fluid.

Author: John C. Sabatino, MD, MSD

Drasin TE, Anderson SW, et al. MDCT Evaluation of Blunt Abdominal Trauma: Clinical Significance of Free Intraperitoneal Fluid in Males With Absence of Identifiable Injury. AJR; 2008;191 (December): 1821-1826

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