Urinary bladder displacement from its regular topography happens due to two main factors. The first one, commonly reported, is related to weakness of pelvic ligaments, often seen in male and elderly dogs that develop perineal hernia. The second one is related to the increasing of intra abdominal pressure due to trauma or strength during birth, which causes exteriorization of the bladder through the vagina. In this instance, the exteriorization of the urinary bladder also was observed. However it has happened through rectal laceration after a motor trauma. A non-breed male dog, 6kg, 1 year old, was attended at the Veterinary Hospital of University of Franca after 20 minutes that it had been hit by a car. Physical examination detected a rounded mass prolapsed within the anus, with red color and necrotic areas. It also presented abdominal sensibility in abdominal palpation. The x-ray showed complete fracture in the body of left ilium and after contrasted retrograde urethrocystography it was noted that the urinary bladder was not in its regular anatomic place. Laparotomy was performed and the bladder, after its complete emptying, was re-introduced through the rectum by the assistant at the same time in which the surgeon pulled it into the cavity through the traumatic orifice of the rectal mucous membrane. Partial dorsal cystectomy was performed (around 75%) due to the extensive necrotic area, when it was maintained only the bladder trigone region. The vesical wall was sutured using Cushing with nylon 4-0 and the orifice of the rectum was sutured with nylon 4-0 in simple separate standard. The reduction of the fracture was proceeded by rectum palpation. The oral medication constituted of ampicillin (22mg/kg), metronidazole (15mg/kg), Dipirona (25mg/kg), carprofen (2.2mg/kg) and of topical spray of rifampicin on the surgical wound. However, after two weeks of the surgery the animal went to death without motives apparently. Pelvic fractures are common in motor traumas, and in this case it was observed the laceration of the rectum by a bone fragment of the ilium, that caused prolapse of the bladder. Probably it might have happened because the animal was a male dog, in which the proximity between bladder and rectum being bigger than in females. It is worth emphasizing the importance of the realization of vesical x-ray contrasted for differentiation of other pathologies.