Usefulness of diffusion-weighted imaging in the evaluation of renal masses.
OBJECTIVE
The objective of our study was to assess the value of diffusion-weighted imaging in differentiating among the various subgroups of renal masses.


METHODS
This retrospective study measured the apparent diffusion coefficients (ADCs) of renal masses. Malignant lesions were confirmed with surgical pathology results. Benign cystic lesions were stable without treatment for a minimum follow-up of 24 months.


RESULTS
There were 20 and 22 patients, respectively, with benign lesions (three abscess, 31 cysts) and malignant lesions (17 clear cell, five papillary, one chromophobe, and two transitional cell cancers). The malignant lesions were larger than the benign lesions (mean diameter, 4.2 vs 2.6 cm, respectively; p = 0.01, Student's t test). The ADC values of the benign lesions were significantly higher than those of the malignant lesions (mean, 2.72 vs 1.88 x 10(-3) mm(2)/s; p < 0.0001). The ADCs of the 31 benign cysts were significantly higher than those of the seven cystic renal cancers (2.77 vs 2.02 x 10(-3) mm(2)/s; p < 0.001). There was no significant difference between the ADCs of clear cell cancers and non-clear cell cancers (1.85 vs 1.97 x 10(-3) mm(2)/s; p = 0.18), but an ADC of less than 1.79 x 10(-3) mm(2)/s was seen only with clear cell cancer. The ADCs of high-grade clear cell cancers (Fuhrman grades III and IV) tended to be lower than those of low-grade clear cell cancers (1.77 vs 1.95 x 10(-3) mm(2)/s; p = 0.12). Among the clear cell cancers, an ADC value of greater than 2.12 x 10(-3) mm(2)/s was seen only with low-grade histology. For differentiating benign from malignant lesions, receiver operating characteristic (ROC) analysis showed an area under the ROC curve of 0.989 (95% CI, 0.919-0.996; p < 0.0001).


CONCLUSIONS
ADC measurements may aid in differentiating among the various subgroups of renal masses, particularly benign cystic lesions from cystic renal cell cancers.
Sandrasegaran
Kumaresan
K
Department of Radiology, Indiana University School of Medicine, Indianapolis, 46202, USA. ksandras@iupui.edu
Sundaram
Chandru P
CP
Ramaswamy
Raja
R
Akisik
Fatih M
FM
Rydberg
Magnus P
MP
Lin
Chen
C
Aisen
Alex M
AM
D000328:Adult; D000368:Aged; D002292:Carcinoma, Renal Cell / Q000175:diagnosis* / Q000473:pathology; D003287:Contrast Media; D003937:Diagnosis, Differential; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods*; D005260:Female; D006801:Humans; D007680:Kidney Neoplasms / Q000175:diagnosis* / Q000473:pathology; D008297:Male; D008536:Meglumine / Q000031:analogs & derivatives; D008875:Middle Aged; D009942:Organometallic Compounds; D012372:ROC Curve; D012189:Retrospective Studies; D018709:Statistics, Nonparametric
D003287:Contrast Media; D009942:Organometallic Compounds; C064572:gadobenic acid; D008536:Meglumine