Relationship of Spontaneous Passage of Ureteral Calculi to Stone Size and Location as Revealed by Unenhanced Helical CT

OBJECTIVE. Prior studies using radiography have examined the relationship of ureteral stone size and location to the probability of spontaneous passage. Given the improved accuracy and new role of unenhanced CT in the diagnosis of acute ureterolithiasis, we studied the relationship of stone size and location as determined by unenhanced CT to the rate of spontaneous passage.MATERIALS AND METHODS. Over a 29-month period, 850 patients with acute flank pain were evaluated with unenhanced CT. Confirmation of the CT diagnosis was obtained retrospectively for 172 patients with ureteral stones: 115 stones passed spontaneously and 57 required intervention. Stone size was defined as the maximum diameter within the plane of the axial CT section. Stone location was classified as proximal ureter (above the sacroiliac joints), mid ureter (overlying the sacroiliac joints), distal ureter (below the sacroiliac joints), and ureterovesical junction.RESULTS. The spontaneous passage rate for stones 1 mm in diameter was 87%; f...