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Pearls and Pitfalls in the Diagnosis of Ureterolithiasis with Unenhanced Helical CT¹

(CME available in print version and on RSNA Link)

¹ From the Department of Diagnostic Radiology, Wilford Hall Medical Center (59 MDW/MTRD), 2200 Bergquist Dr, Suite 1, Lackland Air Force Base, TX 78236-5302. Presented as a scientific exhibit at the 1998 RSNA scientific assembly. Received April 8, 1999; revisions requested April 20 and received May 26; accepted May 26. Address reprint requests to N.C.D. (e-mail: ncdalrymple@earthlink.net).

View larger version (152K): [in a new window]   Figure 1.   Readily apparent perinephric stranding. Axial CT scan shows stranding of the fat surrounding the left kidney and proximal left ureter. In addition, the left kidney is enlarged, with dilatation of the intrarenal collecting system.

View larger version (164K): [in a new window]   Figure 2.   Subtle perinephric stranding. On an axial CT scan, the interface between the lower pole of the left kidney with the surrounding fat is indistinct, indicating mild stranding of the perinephric fat. In contrast, margins of the lower pole of the right kidney are well defined.

View larger version (165K): [in a new window]   Figure 3a.   Extrarenal pelvis. (a) Axial CT scan shows apparent dilatation of the left renal pelvis. (b) Axial CT scan obtained at a slightly lower level shows that the extrarenal pelvis tapers rapidly to a normal proximal ureter that is not dilated.

View larger version (158K): [in a new window]   Figure 3b.   Extrarenal pelvis. (a) Axial CT scan shows apparent dilatation of the left renal pelvis. (b) Axial CT scan obtained at a slightly lower level shows that the extrarenal pelvis tapers rapidly to a normal proximal ureter that is not dilated.

View larger version (162K): [in a new window]   Figure 4.   Collecting system dilatation. Axial CT scan shows dilated, fluid-filled structures that partially obliterate the renal sinus fat in the lower pole of the left kidney. Smaller, rounded structures in the renal sinus of the right kidney represent the normal collecting system.

View larger version (137K): [in a new window]   Figure 5a.   Unilateral absence of the white pyramid as a sign of urinary tract obstruction. (a) Axial CT scan of a patient with a stone in the distal left ureter shows the renal pyramids, which appear hyperattenuating in the right kidney (arrows) and isoattenuating relative to renal parenchyma in the left kidney. (b) CT image of another patient reveals hyperattenuating pyramids in the left kidney and isoattenuating pyramids in the obstructed right kidney, which has a horizontal axis.

View larger version (135K): [in a new window]   Figure 5b.   Unilateral absence of the white pyramid as a sign of urinary tract obstruction. (a) Axial CT scan of a patient with a stone in the distal left ureter shows the renal pyramids, which appear hyperattenuating in the right kidney (arrows) and isoattenuating relative to renal parenchyma in the left kidney. (b) CT image of another patient reveals hyperattenuating pyramids in the left kidney and isoattenuating pyramids in the obstructed right kidney, which has a horizontal axis.

View larger version (149K): [in a new window]   Figure 6.   Normal ureterovesical junctions. Axial CT scan shows bilateral hyperattenuating areas of focal thickening of the posterior bladder wall (arrows), an appearance that represents normal ureterovesical junctions.

View larger version (162K): [in a new window]   Figure 7a.   Retrograde identification of the ureters. (a) Axial CT scan shows the region of the ureterovesical junctions, which are visualized as focal thickening of the posterior bladder wall (arrows). (b) A more cranial image shows a calcification without a soft-tissue rim posterior in the right pelvis. The ureters can be traced back from the ureterovesical junctions (arrows) and are separate from the calcification. (c) On another more proximal image, the distal ureters that could not be followed from above are now readily identified (arrows). The right ureter is clearly anterior to the pelvic calcification, which can be definitively characterized as a phlebolith.

View larger version (160K): [in a new window]   Figure 7b.   Retrograde identification of the ureters. (a) Axial CT scan shows the region of the ureterovesical junctions, which are visualized as focal thickening of the posterior bladder wall (arrows). (b) A more cranial image shows a calcification without a soft-tissue rim posterior in the right pelvis. The ureters can be traced back from the ureterovesical junctions (arrows) and are separate from the calcification. (c) On another more proximal image, the distal ureters that could not be followed from above are now readily identified (arrows). The right ureter is clearly anterior to the pelvic calcification, which can be definitively characterized as a phlebolith.

View larger version (167K): [in a new window]   Figure 7c.   Retrograde identification of the ureters. (a) Axial CT scan shows the region of the ureterovesical junctions, which are visualized as focal thickening of the posterior bladder wall (arrows). (b) A more cranial image shows a calcification without a soft-tissue rim posterior in the right pelvis. The ureters can be traced back from the ureterovesical junctions (arrows) and are separate from the calcification. (c) On another more proximal image, the distal ureters that could not be followed from above are now readily identified (arrows). The right ureter is clearly anterior to the pelvic calcification, which can be definitively characterized as a phlebolith.

View larger version (169K): [in a new window]   Figure 8a.   Soft-tissue rim sign in the ureter. (a) Axial CT scan shows a rim of soft tissue surrounding a stone in the midportion of the left ureter. (b) On an axial CT scan of a different patient, no soft tissue is present around a gonadal vein phlebolith. The normal left ureter was followed from above and identified as separate from the calcification (arrow).

View larger version (178K): [in a new window]   Figure 8b.   Soft-tissue rim sign in the ureter. (a) Axial CT scan shows a rim of soft tissue surrounding a stone in the midportion of the left ureter. (b) On an axial CT scan of a different patient, no soft tissue is present around a gonadal vein phlebolith. The normal left ureter was followed from above and identified as separate from the calcification (arrow).

View larger version (163K): [in a new window]   Figure 9.   Soft-tissue rim sign in the pelvis. Axial CT scan shows a rim of soft tissue surrounding a stone in the distal left ureter. A phlebolith in the posterior right pelvis is surrounded by fat.

View larger version (168K): [in a new window]   Figure 10a.   Differentiation of a ureterovesical junction stone from a stone that has passed into the bladder. (a) Axial CT scan of a patient with right flank pain, obtained with the patient supine, shows a stone adjacent to the right posterior bladder wall. Differential diagnosis includes a passed versus ureterovesical junction stone. (b) On a scan obtained with the patient placed prone, the stone does not fall anteriorly, indicating the stone is still within the ureterovesical junction. (c) Axial CT scan of another patient shows a stone posteriorly in the bladder when the patient is supine. (d) On a scan obtained with the second patient placed prone, the stone moves freely within the bladder and rests on the anterior bladder wall.

View larger version (166K): [in a new window]   Figure 10b.   Differentiation of a ureterovesical junction stone from a stone that has passed into the bladder. (a) Axial CT scan of a patient with right flank pain, obtained with the patient supine, shows a stone adjacent to the right posterior bladder wall. Differential diagnosis includes a passed versus ureterovesical junction stone. (b) On a scan obtained with the patient placed prone, the stone does not fall anteriorly, indicating the stone is still within the ureterovesical junction. (c) Axial CT scan of another patient shows a stone posteriorly in the bladder when the patient is supine. (d) On a scan obtained with the second patient placed prone, the stone moves freely within the bladder and rests on the anterior bladder wall.

View larger version (160K): [in a new window]   Figure 10c.   Differentiation of a ureterovesical junction stone from a stone that has passed into the bladder. (a) Axial CT scan of a patient with right flank pain, obtained with the patient supine, shows a stone adjacent to the right posterior bladder wall. Differential diagnosis includes a passed versus ureterovesical junction stone. (b) On a scan obtained with the patient placed prone, the stone does not fall anteriorly, indicating the stone is still within the ureterovesical junction. (c) Axial CT scan of another patient shows a stone posteriorly in the bladder when the patient is supine. (d) On a scan obtained with the second patient placed prone, the stone moves freely within the bladder and rests on the anterior bladder wall.

View larger version (159K): [in a new window]   Figure 10d.   Differentiation of a ureterovesical junction stone from a stone that has passed into the bladder. (a) Axial CT scan of a patient with right flank pain, obtained with the patient supine, shows a stone adjacent to the right posterior bladder wall. Differential diagnosis includes a passed versus ureterovesical junction stone. (b) On a scan obtained with the patient placed prone, the stone does not fall anteriorly, indicating the stone is still within the ureterovesical junction. (c) Axial CT scan of another patient shows a stone posteriorly in the bladder when the patient is supine. (d) On a scan obtained with the second patient placed prone, the stone moves freely within the bladder and rests on the anterior bladder wall.

View larger version (149K): [in a new window]   Figure 11a.   Protease inhibitor deposition in a 35-year-old man with HIV disease taking indinavir who presented with right flank pain radiating to the right groin. (a) Axial CT scan of the kidneys shows dilatation of the right renal collecting system, as well as mild stranding of the perinephric fat medial to the lower pole of the right kidney. (b) A more inferior image shows dilatation of the right ureter (arrow). (c) Another more inferior scan shows that the right ureter remains dilated to the ureterovesical junction (arrow). No calcification was identified. (d) Subsequent retrograde ureterogram shows multiple filling defects in the distal right ureter. Stricture of the ureter distal to the indinavir fragments is likely caused by recent stone impaction near the ureterovesical junction.

View larger version (138K): [in a new window]   Figure 11b.   Protease inhibitor deposition in a 35-year-old man with HIV disease taking indinavir who presented with right flank pain radiating to the right groin. (a) Axial CT scan of the kidneys shows dilatation of the right renal collecting system, as well as mild stranding of the perinephric fat medial to the lower pole of the right kidney. (b) A more inferior image shows dilatation of the right ureter (arrow). (c) Another more inferior scan shows that the right ureter remains dilated to the ureterovesical junction (arrow). No calcification was identified. (d) Subsequent retrograde ureterogram shows multiple filling defects in the distal right ureter. Stricture of the ureter distal to the indinavir fragments is likely caused by recent stone impaction near the ureterovesical junction.

View larger version (164K): [in a new window]   Figure 11c.   Protease inhibitor deposition in a 35-year-old man with HIV disease taking indinavir who presented with right flank pain radiating to the right groin. (a) Axial CT scan of the kidneys shows dilatation of the right renal collecting system, as well as mild stranding of the perinephric fat medial to the lower pole of the right kidney. (b) A more inferior image shows dilatation of the right ureter (arrow). (c) Another more inferior scan shows that the right ureter remains dilated to the ureterovesical junction (arrow). No calcification was identified. (d) Subsequent retrograde ureterogram shows multiple filling defects in the distal right ureter. Stricture of the ureter distal to the indinavir fragments is likely caused by recent stone impaction near the ureterovesical junction.

View larger version (152K): [in a new window]   Figure 11d.   Protease inhibitor deposition in a 35-year-old man with HIV disease taking indinavir who presented with right flank pain radiating to the right groin. (a) Axial CT scan of the kidneys shows dilatation of the right renal collecting system, as well as mild stranding of the perinephric fat medial to the lower pole of the right kidney. (b) A more inferior image shows dilatation of the right ureter (arrow). (c) Another more inferior scan shows that the right ureter remains dilated to the ureterovesical junction (arrow). No calcification was identified. (d) Subsequent retrograde ureterogram shows multiple filling defects in the distal right ureter. Stricture of the ureter distal to the indinavir fragments is likely caused by recent stone impaction near the ureterovesical junction.