LOW ATTENUATION OF ACUTE TRAUMATIC HEMOPERITONEUM ON CT SCANS

OBJECTIVE. This study was undertaken to determine the incidence of low attenuation values in intraperitoneal hemorrhage, which could be conf used with ascites. MATERIALS AND METHODS. We retrospectively analyzed the CT scans of 42 consecutive patients with hepatic or splenic lacera tions and intraperitoneal fluid after blunt abdominal trauma, Patients were excluded if they had prior peritoneal lavage, bladder or bowel i njury, or low hematocrit values. Intraperitoneal fluid was categorized by the site of accumulation (perihepatic, perisplenic, Morison's pouc h, paracolic gutters, or pelvis), The amount of fluid in each intraper itoneal location was categorized as small, moderate, or large. Attenua tion values were obtained from each intraperitoneal site, and overall mean attenuation values were determined for each patient, We correlate d the size of each fluid collection with the attenuation value. We als o compared attenuation Values at locations adjacent to the site of eac h injury with those at other intraperitoneal sites, We then evaluated technical factors that could have lowered attenuation values, includin g CT miscalibration, volume averaging, and beam-hardening artifacts. R ESULTS. For the 42 patients, we measured 131 separate attenuation valu es. Attenuation values ranged from 0 to 80 H, with attenuation at 24% of sites (32/131) measuring less than 20 H. Only 16% of sites (21/131) had attenuation values greater than 45 H. Attenuation at the remainin g 78 sites (60%) measured from 20 to 45 H. All intraperitoneal locatio ns except the pelvis had mean attenuation values significantly lower t han 40 H. Mean attenuation values (determined by averaging measurement s from different intraperitoneal sites) were also calculated for each patient. Only 6 (14%) of 42 patients had mean attenuation values great er than 40 H, whereas 4 (10%) of 42 patients had mean attenuation valu es less than 20 H. The remaining 32 patients (76%) had mean attenuatio n values between 21 and 40 H, Patients with hepatic lacerations showed no significant difference (p = .3509) in attenuation between perihepa tic fluid and the remainder of intraperitoneal fluid. However, in pati ents with splenic lacerations, perisplenic fluid had a significantly h igher (p = .0013) attenuation value (43 H) than did fluid at other int raperitoneal locations. CONCLUSION. Low attenuation measurements for a cute hemoperitoneum represented a common finding that was not attribut able to technical factors or underlying anemia. Fluid with attenuation values less than 20 H in acute trauma should not be dismissed as asci tic fluid.