Differentiation of renal neoplasms from high-density cysts: use of attenuation changes between the corticomedullary and nephrographic phases of computed tomography.
OBJECTIVE
The current study evaluated attenuation changes for proven renal neoplasms between the corticomedullary and the nephrographic phases of a contrast-enhanced computed tomographic (CT) scan as a possible means for differentiating these tumors from the cysts of the kidney when high-density renal masses are detected on a CT scan that does not include a noncontrast baseline.


METHODS
We retrospectively reviewed the CT scans performed on 20 patients with 21 biopsy-proven renal neoplasms, which had been done using standard contrast-enhanced computed tomography only. Attenuation values for the 21 renal neoplasms and for 23 simple cysts, used as an internal control, were measured and recorded from the 2 phases of enhancement. The difference in attenuation between the 2 phases of enhancement for each mass was calculated. Data for the neoplasms and cysts were compared with published data for enhancement changes for proven high-density renal cysts.


RESULTS
The mean absolute value change in attenuation between the corticomedullary and the nephrographic phases for renal neoplasms was 22 Hounsfield units (HU) (range, 1.0-48 HU) and 1 HU (range, 0.1-3.3 HU) for simple cysts. Only one renal neoplasm (5%) changed to less than 10 HU.


CONCLUSIONS
Almost all renal neoplasms studied had an attenuation change of more than 10 HU, either increased or decreased, between 2 phases of a contrast-enhanced CT scan separated by 50 seconds. The results suggest that if the attenuation of a renal tumor changes by more than 10 HU between phases of a contrast-enhanced computed tomography, then the diagnosis of renal neoplasm is very likely. High-attenuation renal masses which change less than 10 HU between the corticomedullary and tubular phases are most likely high-density cysts, but neoplasm is possible.
Zagoria
Ronald J
RJ
Department of Radiology, Wake Forest University School of Medicine, Winston-Salem, NC 27157, USA. rzagoria@wfubmc.edu
Gasser
Tyler
T
Leyendecker
John R
JR
Bechtold
Robert E
RE
Dyer
Raymond B
RB
D000368:Aged; D000369:Aged, 80 and over; D003937:Diagnosis, Differential; D005260:Female; D006801:Humans; D052177:Kidney Diseases, Cystic / Q000000981:diagnostic imaging*; D007680:Kidney Neoplasms / Q000000981:diagnostic imaging*; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies; D014057:Tomography, X-Ray Computed / Q000379:methods*