Abstract
PurposeTo retrospectively evaluate whether prone CT scanning is superior to supine scanning for correct localization of distal urinary calculi in patients with acute flank pain.MethodsConsecutively performed unenhanced CT scans in patients with acute flank pain were retrospectively analyzed in 150 patients in supine and another 150 patients in prone position. Images were reviewed by two radiologists on consensus. Findings in both groups were compared using two-sided Fisher Exact tests and Wilcoxon–Mann–Whitney test.ResultsUrinary calculi were found in 67% of patients in each group. In the supine scanning group, there were 16 cases, in which the location of the stone was equivocal being either located intramurally at the ureterovesical junction (UVJ) or having already passed into the bladder. In contrast, in the prone imaging group all distal stones could be allocated accurately, either to the intramural UVJ or the urinary bladder (37 intramural UVJ stones and six bladder stones in prone scanning group vs. 21 intramural UVJ stones and one bladder stone when scanned supine).ConclusionProne scanning is superior to supine CT scanning for acute flank pain to accurately distinguish intramural UVJ stones from stones that have already passed into the bladder, a distinction which influences patient management.
Highlights
To retrospectively evaluate whether prone computed tomography (CT) scanning is superior to supine scanning for correct localization of distal urinary calculi in patients with acute flank pain
Prone scanning is superior to supine CT scanning for acute flank pain to accurately distinguish intramural ureterovesical junction (UVJ) stones from stones that have already passed into the bladder, a distinction which influences patient management
In the prone imaging group, all stones could be unequivocally located to the intramural UVJ (37 cases, 37%) or to the urinary bladder (6 cases, 6%), and so there were no cases with equivocal stone location with regard to UVJ vs. urinary bladder (Table 1)
Summary
To retrospectively evaluate whether prone CT scanning is superior to supine scanning for correct localization of distal urinary calculi in patients with acute flank pain. Conclusion: Prone scanning is superior to supine CT scanning for acute flank pain to accurately distinguish intramural UVJ stones from stones that have already passed into the bladder, a distinction which influences patient management. Levine et al demonstrated that the location of a considerable number of distal calculi remains equivocal in conventional supine CT scans (Fig. 2) They suggested that additional prone scanning is needed in these cases to accurately locate stones to UVJ or urinary bladder [6]. Due to their work and upon expert consensus at our department, we changed the standard protocol for patients referred to CT imaging with acute flank pain from supine to prone scanning effective from June 2008. This retrospective review was designed to further validate prone scanning as standard protocol in 150 consecutive patients with acute flank pain and to perform a comparison to 150 consecutively performed supine scans for the same indication before changing the protocol
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