DETECTION OF URETERAL CALCULI IN PATIENTS WITH SUSPECTED RENAL COLIC - VALUE OF REFORMATTED NONCONTRAST HELICAL CT

OBJECTIVE. The purpose of this study was to determine the Value of ref ormatted noncontrast helical CT in patients with suspected renal colic . We hoped to determine whether this technique might create images acc eptable to both radiologists and clinicians and replace our current pr otocol of sonography and abdominal plain film. SUBJECTS AND METHODS. T hirty-four consecutive patients with signs and symptoms of renal colic were imaged with both noncontrast helical CT and a combination of pla in film of the abdomen and renal sonography. Reformatting of the helic al CT data was performed on a workstation to create a variety of refor matted displays. The correlative studies were interpreted by separate blinded observers. Clinical data, including the presence of hematuria and the documentation of stone passage or removal, were recorded. RESU LTS. Findings on 18 CT examinations were interpreted as positive for t he presence of ureteral calculi; 16 of these cases were determined to be true positives on the basis of later-documented passage of a calcul us, Thirteen of the 16 cases proved to be positive were interpreted as positive far renal calculi using the combination of abdominal plain f ilm and renal sonography. The most useful CT reformatting technique wa s curved planar reformatting of the ureters to determine whether a ure teral calculus was present. CONCLUSION. In this study, noncontrast hel ical CT was a rapid and accurate method for determining the presence o f ureteral calculi causing renal colic. The reformatted views produced images similar in appearance to excretory urograms, aiding greatly in communicating with clinicians, Limitations on the technique include t he time and equipment necessary for reformatting and the suboptimal qu ality of reformatted images when little retroperitoneal fat is present .