OBJECTIVE We investigated the role of Helical Computed Tomography (CT) in the evaluation of low or high flow vascular injuries in patients with blunt pelvic trauma. METHODS From May 1998 to December 1999, forty-nine patients (32 men and 17 women, ranging in age 14-59 years) with acute symptoms from blunt pelvic trauma were submitted to Computed Tomography (CT). A conventional radiography of the pelvis had been performed in all cases. CT was performed with a helical unit (thickness 8 mm, reconstruction interval 8 mm, pitch 1.5) after intravenous contrast agent (150-180 mL) rapid infusion (4-5 mL/s, 60 s acquisition delay from bolus starting) and using a power injector. A second spiral acquisition was performed in all cases from the iliac roofs to the inferior border of the pubic symphysis. Vascular hemorrhage was considered as low flow when the hematoma appeared as a focal homogeneous density area and as high flow when associated with contrast agent extravasation. Moreover, traumatic assessment included evaluation of the hematoma, of the leakage site and of the involved vessel. RESULTS Radiologic examination of the pelvis revealed fractures in 35/49 patients (71.4%). Helical CT allowed us to identify low flow hemorrhage in 37 patients, affected with hematomas from fracture of the iliac wing or of the sacrum (14 cases), tear of the pelvic (3 cases) or extrapelvic (4 cases) muscular structures, or injury of the venous plexus (20 cases). In four patients two vascular injuries were detected. High flow hemorrhage was seen in 12 patients, who had Helical CT findings of contrast agent extravasation along the common iliac vein (3 cases), external iliac artery (3 cases), internal iliac artery (4 cases), internal pudendal artery (1 case), obturator artery (1 case), inferior epigastric artery (2 cases), superior gluteal artery (2 cases), inferior gluteal artery (1 case), cremasteric artery (1 case). In 6 patients with high flow hemorrhage, two vascular injuries were shown. In all these patients, an extraperitoneal hematoma was associated with the contrast agent extravasation. CONCLUSIONS Fractures of the pelvic ring generally result from severe trauma. Management of these injuries must include not only treatment of the skeletal trauma but also of the associated shock and complications. Major blood loss usually occurs as a result of bleeding from the branches of the internal iliac artery. With respect to pelvic plain radiography, CT provides superior detailing of fractures, position of fracture fragments and extent of diastasis of the sacroiliac joints and pubic symphysis. Moreover CT provides diagnostic information regarding the presence or absence of pelvic bleeding and can identify the site of bleeding. In our experience, Helical CT allows us to distinguish high flow hemorrhage, where vascular injuries must be treated first, from low flow hemorrhage which can be managed differently.