Purpose Despite the routine use of helical CT in diagnosis of renal colic, there are recent concerns regarding the radiation exposure, overuse and costs. We attempted in this retrospective study to evaluate the accuracy of ultrasound (gray-scale and color Doppler with twinkling), KUB and urinalysis in diagnosis of renal colic due to ureteral calculi presented in Emergency Room. Materials and Methods A total of 939 consecutive cases of renal colic presented to ER have been managed and evaluated by ureteral ultrasound, KUB and urinalysis for the presence of ureteral stones. Non-confirmatory cases were subjected to Helical CT examination. Results Renal and ureteral ultrasound (gray-scale) alone detected ureteral calculi in 615 cases (65.4%) and after utilizing Color Doppler Ultrasound with twinkling the diagnosis was made with confidence in 935 cases (99.6%) but 4 (0.4%). KUB showed radiopaque stones in 503 (53.6%) patients and no stones were detected in 436 (46.4%). Microhematuria presented in 835 (88.9%) cases while absent in 102 (10.9%). There were 190 (20.3%), 77 (8.2%) and 671 (71.5%) patients with upper, middle and lower ureteral stones respectively. The simultaneous positive findings in US and KUB with microhematuria were found only in 453 (48.2%) cases. Conclusions The use of Color Doppler ultrasound with twinkling increased the detection rate of ureteral stones in acute renal colic patients presented to ER with less radiation exposure. Ultrasound examination as a single modality is superior to KUB and urinalysis in initial diagnosis of renal colic.