To determine the value of secondary signs of ureteral obstruction on helical unenhanced CT in
diagnosing or excluding ureteral stone disease.
Over a period of 15 months, we prospectively analysed the CT scans of 283 patients with acute flank
pain for the presence of ureteral stones & associated signs of ureteral obstruction. 105 patients had no
confirmatory imaging studies or surgery & were unable to be contacted for follow up .These were
excluded from the study. In the remaining 178 patients confirmatory data were availabe & thus were
included in the study. Ureteral stone disease was confirmed to be present in 114 patients & absent in 64
patients. For each patient, we determined the presence or absence of ureteral stone, ureteral or
collecting system dilatation, perinephric stranding, &renal parenchymal thickening. We also noted the
presence or absence of the (" tissue rim" sign) surrounding ureteral stones & extraurinary calcifications.
Hydroureter was the sign with the highest sensitivity (92 %) & highest specificity (92%), While
hydroureter had the highest specificity (95 %) & highest PPV (97%). The combination of unilateral
hydroureter & 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.
In patients having acute flank pain with suspected ureteral stone disease imaged with unenhanced CT ,
secondary signs including hydroureter , hydronephrosis , perinephric fat stranding , & renal
parenchymal thickening are very common & provides supportive evidence that an acute obstructive
process is present & that the urinary tract is likely responsible for the patients' complaints even when
the ureteral stone itself could not be identified on CT .