The roentgen diagnosis of pelvic extraperitoneal effusion

Extraperitoneal, perivesical pelvic effusions may be hemorrhagic or uriniferous, the latter resulting from extraperitoneal rupture of the bladder or disruption of the posterior urethra. The effusions may be recognized on anteroposterior radiographs of the pelvis by (a) displacement of the bladder (small effusion); (b) obliteration of the normal soft-tissue anatomy within the pelvis (moderate effusion); and (c) upward displacement of the pelvic ileal loops and extension of the effusion into the flank stripes (large effusion). Perivesical effusions most frequently accompany anterior pelvic arch injuries, i.e., double vertical and Malgaigne fractures and fractures involving, or separation of, the pubic symphysis.