an injury to the upper urinary tract with urinary extravasation caused by blunt abdominal trauma is uncommon and often unrecognized in an initial evaluation. a late diagnosis of this injury significantly increases morbidity. two cases are discussed, one with avulsion of right upper ureter and the other one with parenchymal and right renal pelvis laceration with delayed diagnosis and severe complications subsequent to a direct blunt abdominal trauma. knowledge of the mechanism of trauma and the assessment of local signs and symptoms are important data for suspecting ureteropelvic injury regardless of the trauma severity. the absence of initial hematuria is not uncommon and their presence and degree is unrelated to the severity of the injury. an abdominal computed tomography with iv contrast evaluated in delayed excretory phase allows an early detection of extravasation of urine.