Answer
In stage I or II disease, conditions such as chronic pyelitis, tuberculosis, and xanthogranulomatous pyelonephritis may mimic TCC.
In stage III or IV disease, CT cannot be used to distinguish edema, infection, inflammatory changes, or hemorrhage from tumor. All of these processes may cause inhomogeneous peripelvic attenuation that is indistinguishable from that caused by the infiltration of fat by tumor. Superimposed pyelonephritis can cause inhomogeneous renal enhancement and thus give a false interpretation of invasion by underlying TCC. Occasionally, renal cell carcinoma may simulate TCC with renal parenchymal infiltration.
The characteristic attenuation of a TCC lesion is normally sufficiently different from renal tract filling defects of other causes, such as calculi and blood clots, to enable the correct diagnosis. However, a blood clot may be confused with a hyperattenuating TCC, particularly in the early stages of the disease. Also, in a patient with undiagnosed early-stage TCC, inhomogeneous renal fat attenuation of any cause may hinder accurate diagnosis.
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A 21-year old man presented with a history of intermittent hematuria of 1-month duration. Three months previously, he had been assaulted and kicked in the right loin. A 30-minute intravenous urogram shows a moderate right hydronephrosis without filling of the renal pelvis, although some contrast material has passed into the upper ureter. Note also a polypoid intraluminal filling defect within the left side of the bladder (arrow).
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Left, transverse sonogram of the right kidney in the same patient as in the previous image shows a centrally placed solid mass within the renal pelvis with low-level echoes and with proximal hydronephrosis. Right, transverse sonogram through the bladder shows a polypoid filling defect in the bladder.
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Nonenhanced (top) and enhanced (bottom) CT scans through the kidneys show a mass in the right renal pelvis. The histologic diagnosis was a right renal pelvis neurofibroma and a bladder transitional cell carcinoma.
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An intravenous urogram in a 36-year old woman who presented with evidence of a urinary tract infection and gross hematuria. A 10-minute intravenous urogram shows a filling defect in the lower pole calyx on the right. A provisional diagnosis of transitional cell carcinoma was made. Subsequent investigations and the course of events proved that the filling defect was caused by a blood clot related to the hematuria secondary to acute pyelonephritis.
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Localized views of the right vesicoureteric junction obtained after intravenous urography shows a polypoid filling defect in the lower right ureter due to a transitional cell carcinoma.
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A 10-minute intravenous urogram in a 56-year-old man presenting with hematuria. The image shows a mass lesion in the right renal pelvis that bisects the renal sinus and splays the adjacent calyces.
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Longitudinal sonogram obtained through the right kidney shows a hypoechoic mass bisecting the renal sinus fat. The mass is a transitional cell carcinoma.
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Nonenhanced (top) and enhanced (bottom) CT scans obtained through the kidneys in a 73-year-old woman show a mass in the left renal pelvis is a transitional cell carcinoma.
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Left retrograde pyelogram shows marked irregularity of the infundibulum of the upper pole calyx caused by infiltration by transitional cell carcinoma. This information was unavailable on the CT scans.
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Top, Longitudinal sonogram obtained thorough the left kidney in a 58-year-old man presenting with hematuria shows a normal left kidney. Bottom, More medial section through the same kidney shows a vague isoechoic mass in the upper of the kidney. Whether this finding represented an artifact or a genuine lesion was unclear. Technetium-99m dimercaptosuccinate (99mTc DMSA) scanning is good modality for differentiating a renal pseudomass from a genuine mass.
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Left posterior view of a technetium-99m dimercaptosuccinate (99mTc DMSA) scan shows a photon-deficient mass in the upper pole of the left kidney; this finding indicates a genuine mass in this region. At partial nephrectomy, transitional cell carcinoma was confirmed.
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Scout radiograph in a 53-year-old man presenting with hematuria shows a few small vague opacities in the left renal area; these are suggestive of renal calculi.
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Intravenous urogram shows 2 filling defects: 1 in the upper pole and 1 in the lower-pole calyces. Conventional tomographic results (bottom) confirm the findings.
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Longitudinal sonogram through left kidney shows that the filling defects are due to calculi. Ultrasonography is an efficient means for differentiating between radiolucent calculi and uroepithelial tumors.
