Unenhanced CT Scanning in Acute Flank Pain: Value of Secondary Signs of Ureteral Obstruction

Abstract

ABSTRACT:BACKGROUND:To determine the value of secondary signs of ureteral obstruction on helical unenhanced CT indiagnosing or excluding ureteral stone disease.METHODS:Over a period of 15 months, we prospectively analysed the CT scans of 283 patients with acute flankpain for the presence of ureteral stones & associated signs of ureteral obstruction. 105 patients had noconfirmatory imaging studies or surgery & were unable to be contacted for follow up .These wereexcluded from the study. In the remaining 178 patients confirmatory data were availabe & thus wereincluded in the study. Ureteral stone disease was confirmed to be present in 114 patients & absent in 64patients. For each patient, we determined the presence or absence of ureteral stone, ureteral orcollecting system dilatation, perinephric stranding, &renal parenchymal thickening. We also noted thepresence or absence of the (" tissue rim" sign) surrounding ureteral stones & extraurinary calcifications.RESULTS:Hydroureter was the sign with the highest sensitivity (92 %) & highest specificity (92%), Whilehydroureter had the highest specificity (95 %) & highest PPV (97%). The combination of unilateralhydroureter & unilateral perinephric stranding had both the highest PPV (98 %) & NPV (91 %)compared with any individual sign alone . The tissue rim sign was present in (57 %) of urteral stones &in none of the extraurinary calcifications.CONCLUSION:In patients having acute flank pain with suspected ureteral stone disease imaged with unenhanced CT ,secondary signs including hydroureter , hydronephrosis , perinephric fat stranding , & renalparenchymal thickening are very common & provides supportive evidence that an acute obstructiveprocess is present & that the urinary tract is likely responsible for the patients' complaints even whenthe ureteral stone itself could not be identified on CT .