Differentiating Renal Neoplasms From Simple Cysts on Contrast-Enhanced CT on the Basis of Attenuation and Homogeneity.
OBJECTIVE
The purpose of this study is to compare the attenuation and homogeneity of renal neoplasms with those of cysts on contrast-enhanced CT.


METHODS
A total of 129 renal neoplasms and 24 simple cysts were evaluated. Two readers determined whether each mass was qualitatively heterogeneous or homogeneous. Mean, minimum, and maximum attenuation values were measured. Statistical analysis was performed.


RESULTS
A total of 116 heterogeneous renal cell carcinomas (RCCs) (99 clear cell, four papillary, four oncocytic, seven chromophobe, and two unclassified RCCs), 13 homogeneous RCCs (10 papillary, two oncocytic, and one chromophobe RCC), and 24 cysts (all of which were homogeneous) were evaluated. All homogeneous RCCs had mean attenuation values of more than 42 HU, whereas renal cysts had mean attenuation values of up to 30 HU (p < 0.001). Two readers qualitatively and identically categorized all RCCs as homogeneous or heterogeneous (κ = 1.0; p < 0.001).


CONCLUSIONS
Homogeneous simple renal cysts can have mean attenuation values of up to 30 HU, as determined by contrast-enhanced CT, whereas homogeneous RCCs have mean attenuation values as low as 42 HU, with no overlap occurring between the two groups. These data suggest that further evaluation of a homogeneous renal mass with a mean attenuation value of 30 HU or less on a contrast-enhanced CT scan likely is unwarranted.
1 Department of Urology, Yale University School of Medicine, New Haven, CT.
Nnenaya
N
Agochukwu
2 Department of Radiology and Biomedical Imaging, Yale University School of Medicine, 333 Cedar St, Box 208042, New Haven, CT 06520.
Steffen
S
Huber
2 Department of Radiology and Biomedical Imaging, Yale University School of Medicine, 333 Cedar St, Box 208042, New Haven, CT 06520.
Michael
M
Spektor
2 Department of Radiology and Biomedical Imaging, Yale University School of Medicine, 333 Cedar St, Box 208042, New Haven, CT 06520.
Alexander
A
Goehler
2 Department of Radiology and Biomedical Imaging, Yale University School of Medicine, 333 Cedar St, Box 208042, New Haven, CT 06520.
Gary M
GM
Israel
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D003287:Contrast Media; D003937:Diagnosis, Differential; D005260:Female; D006801:Humans; D007089:Image Enhancement / Q000379:methods; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D007472:Iohexol; D052177:Kidney Diseases, Cystic / Q000000981:diagnostic imaging*; D007680:Kidney Neoplasms / Q000000981:diagnostic imaging*; D008297:Male; D008875:Middle Aged; D015588:Observer Variation; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014057:Tomography, X-Ray Computed / Q000379:methods*
D003287:Contrast Media; D007472:Iohexol
Hounsfield units; cysts; homogeneity; kidney; renal neoplasms