Background: Recent evidence indicates that acute hemoperitoneum may have lower than expected attenuation values at CT.
Objective: To characterize the attenuation of acute hemoperitoneum at CT in children following blunt abdominal trauma and to assess the prevalence of low-attenuation fluid.
Materials and methods: The CT scans of 19 consecutive children with isolated hepatic or splenic injury and associated peritoneal fluid were retrospectively analyzed. The attenuation value of peritoneal fluid was assessed in all peritoneal spaces.
Results: Fluid was noted in 53 peritoneal spaces (27 abdominal, 26 pelvic). Fluid attenuation ranged from 20 to 64 HU. The mean fluid attenuation in pelvic spaces (37.5 +/- 9.4 HU) was significantly lower than in abdominal spaces (444.9 +/- 10.2 HU) (P = 0.008). Fluid in 8/26 (31 %) pelvic spaces and 2/27 (7 %) abdominal spaces had attenuation values < or = 30 HU. Fluid surrounding the site of injury (perihepatic or perisplenic space) was significantly higher in attenuation than fluid at other sites (P < 0.001). There was no correlation between the mean attenuation value of peritoneal fluid in each patient and the admission hematocrit (r = -0.14, P = 0.55).
Conclusions: There is great variability in the attenuation of acute hemoperitoneum. Blood in pelvic spaces has significantly lower attenuation than blood in abdominal spaces. Hemoperitoneum in the pelvis has values of < or = 30 HU in approximately one-third of spaces. The attenuation of acute hemoperitoneum does not correlate with hematocrit.