Relationship between duration of pain and secondary signs of obstruction of the urinary tract on unenhanced helical CT

OBJECTIVE, The objective of this study was to investigate the relationship between duration of flank pain and the frequency of secondary signs of uret eral obstruction on unenhanced helical CT. SUBJECTS AND METHODS. The duration of flank pain was prospectively determin ed in 227 consecutive patients diagnosed with acute ureterolithiasis on une nhanced helical CT. These CT studies were evaluated for the presence or abs ence of perinephric stranding, ureteral dilatation, perinephric fluid, coll ecting system dilatation, periureteral stranding, and nephromegaly. The fre quency of each sign was determined as a function of the duration of pain. RESULTS. The frequency of moderate or severe perinephric stranding increase d from 5% at 1-2 hr to 51% at 7-8 hr (p < 0.001); ureteral dilatation incre ased from 84% at 1-2 hr to 97% at more than 8 hr (p < 0.03); moderate or se vere perinephric fluid increased from 0% at 1-2 hr to 22% at 3-4 hr (p < 0. 03); collecting system dilatation increased from 68% at 1-2 hr to 89% at 7- 8 hr (p < 0.03); periureteral stranding increased from 35% at 1-2 hr to 76% at 7-8 hr (p < 0.004); and nephromegaly increased from 40% at 1-2 hr to 54 % at 7-8 hr (p < 0.36). CONCLUSION. All CT secondary signs of ureteral obstruction except nephromeg aly showed a significant increase in frequency as duration of flank pain in creased. This observation may explain why the CT studies of some patients w ith acute ureterolithiasis show negative findings for some or all CT second ary signs of obstruction. Therefore, knowledge of the duration of pain is i mportant when interpreting unenhanced CT studies in patients with acute ure terolithiasis.