A bladder-flap hematoma is generally thought of as a blood collection in a potential space located between the urinary bladder and lower uterine segment (vesicouterine space). These collections can also extend over the bladder and uterus beneath the peritoneal reflection. In this study, ten patients with a bladder-flap hematoma were evaluated for fever, mass, or dropping hematocrit after surgery. No one sonographic appearance is specific for bladder-flap hematoma; however, the diagnosis can be made by finding a mass in the extraperitoneal pelvic space in the postoperative patient.