The evaluation of suspected renal colic: Ultrasound scan versus excretory urography

Patients commonly present to the emergency department with a suspected diagnosis of renal colic. A prospective study of 98 patients presenting with acute flank or abdominal pain or both was conducted to determine the diagnostic accuracy of ultrasound scan compared with excretory urography for the diagnosis of urinary tract calculi. All patients underwent standardized ultrasound scan and excretory urography as independent procedures. Two staff radiologists who reported the procedures were blinded to the results of the other diagnostic test and ultimate clinical outcome. All patients discharged home from the ED were followed to the hospital urology clinic. The diagnosis of urinary calculus was made only by identification of calculus at surgery or by reported passage of a stone by the patient. Of 85 patients available for follow-up study (56 men, 29 women; mean age, 40.5 years; range 18 to 77 years), calculi were identified in 69 (81%). Ultrasound identified calculi in 44 patients (sensitivity, 64%; specificity, 100%). Excretory urography identified calculi in 44 patients (identical sensitivity and specificity). When the presence of obstructive hydronephrosis only was used to diagnose renal calculi, ultrasound scan identified 59 patients (sensitivity, 85%; specificity, 100%) and excretory urography identified 62 patients (sensitivity, 90%; specificity, 94%). When the results of both diagnostic modalities were combined, calculi were identified in 59 patients (sensitivity, 85%; specificity, 100%) and hydronephrosis was seen in 66 patients (sensitivity, 95%; specificity, 94%). Our study shows that the diagnostic abilities of these procedures are equal in the detection of renal calculi. Excretory urography remains the investigation of choice because of its availability and ease of interpretation, but the procedures may be combined in selected cases to improve diagnostic accuracy.