The occult unilateral hydronephrotic kidney is often discovered during the genitourinary evaluation of patients sustaining blunt abdominal trauma. Few cases have been reported documenting the angiographic, computerized tomography (CT), and ultrasound appearances. Two cases are described which demonstrate that relatively minor trauma can precipitate hematuria and hypovolemic shock. Angiography demonstrated the bleeding site in both cases and was utilized in conjunction with other parameters of clinical assessment to plan initial management. CT and ultrasound proved to be useful noninvasive diagnostic parameters for baseline and follow-up studies in patients undergoing conservative management. They accurately demonstrated the degree of hydronephrosis, residual renal parenchymal, and resolving hematoma.