This is known as a pear bladder. The description refers to the shape that the bladder takes when it is compressed from the sides - with the commonest reason being a pelvic haematoma secondary to injury. In this instance there is a large left sided extraperitoneal haematoma compressing the bladder. Other causes include pelvic lipomatosis, lymphadenopathy and lymphocoeles.
An axial CT image shows that the cause in this case is a left sided pelvic haematoma, compressing the bladder and leading to the pear shaped bladder sign.
These CT images were obtained in a delayed phase - infact 20 minutes after contrast administration. This has allowed enough time for the contrast to be excreted via the kidneys into the ureters and urinary bladder. This phase was acquired to check for ureteric or bladder injury. There is no such injury here, just a venous bleed into the pelvis.