Renal colic is one the most common diseases seen in the emergency department. Ultrasound can serve as an initial investigation for detecting stones with or without associated hydronephrosis and is especially useful when avoiding radiation is important. The twinkling artifact in color Doppler aids in the diagnosis of small calculi. Helical CT serves as the imaging modality of choice because of its higher sensitivity in detecting stones. CT may help in diagnosing other nonrenal causes of acute abdominal pain. MR urography is a new modality that can be useful in pregnant women when renal ultrasound findings are equivocal.