Flank pain with hematuria is a common chief complaint in the emergency department (ED).  Patients are often diagnosed with renal calculi or pyelonephritis and discharged with analgesics or antibiotics and follow-up. This case study describes a patient who presented to the ED with a 1 week history of flank pain and hematuria and was subsequently found to have a large renal mass on bedside ultrasound. [West J Emerg Med 2013;14(2):123-126.]