Anqin Li1, Zhen Li1, and Daoyu Hu1
1Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
Synopsis
To
improve understanding of DWI features of complex renal cysts, and compare diagnostic
performance of MRI and CT in discrimination of benign
and malignant masses. Images
of each lesion were analyzed, including size, thickness of wall,
number of septum, enhancement of wall/septum, wall nodule, calcification, and cyst content.
CT and MRI image characteristics were compared with pathology or follow-up
results. The
incidences of high signal intensity on DWI were
significantly higher in malignant than
in benign masses. MRI showed higher AUC than CT for
differentiating benign from malignant masses.
MRI could be useful in improving diagnosis of complex
renal cysts.
Introduction/Purpose
Renal
cystic masses are common and are being detected more and more frequently due to
the increasing use of cross-sectional imaging. 21% of cystic masses show a complex pattern,
making it difficult to identify benign or malignant and subsequent treatment1. At present, the Bosniak
classification criteria based on CT has been widely used to evaluate renal
cystic masses and guide clinical management2. However, due to the low
contrast resolution of CT, the CT-based Bosniak classification criteria have
certain limitations for detecting septa and solid components. In addition,
there are some clinical factors and image findings that are helpful in
identifying benign and malignant, such as body mass index (BMI) of patients and
high signal intensity of solid components on diffusion weighted imaging (DWI), but
are not included in the classification criteria. Therefore, the accuracy of
Bosniak classification criteria only based on CT for the diagnosis of complex
renal cysts remains controversial3.
Studies have shown that the Bosniak criteria can also be useful on MRI4,5. The
purpose of this study was to compare the diagnostic performances of CT and MRI
in the evaluation of renal cystic mass according to pathology and follow-up
results.Materials and Methods
This
study retrospectively analyzed 85 renal cystic masses in 81 patients with CT or
MRI, including 42 patients with DWI (b = 600, 1000 s/mm2). Clinical variables and histopathological results
were recorded. Two radiologists in consensus
analyzed images of each lesion for the size, thickness of wall,
number of septum, enhancement of wall/septum, wall nodule, calcification, and cyst content.
Clinical variables, CT and MRI image
characteristics were compared with pathology or follow-up results to evaluate
the diagnostic performance for renal cystic masses.Results
Of the 85 lesions in 81
patients, histological analysis reported that
31 were malignant, 31
were benign, and no change was found in 23 followed-up lesions (mean follow-up of 17 months). The incidences of
cystic wall thickened, more septa,
measurable enhancement of wall/septum, wall nodule on CT/MRI, and high signal intensity on DWI were
significantly higher in malignant than
in benign masses (CT: P = 0.007, P < 0.001, P = 0.001, P = 0.002, P < 0.001; MRI: P = 0.006, P < 0.001,
P < 0.001, P = 0.020, P < 0.001, P < 0.001). MRI showed
higher area
under the receiver operating characteristic curve (0.951) than CT (0.912) for differentiating benign from malignant
cystic masses (Fig. 1). The images of
several representative cases are shown in Figure 2-4.Discussion
Because
of the superiority in soft tissue resolution, MRI exhibits additional findings
in some cases, such as irregular thickened walls or more septa4,6. In addition, DWI sequence of
MRI can provide additional histological features inside the renal cystic masses6,7. Using contrast-enhanced MRI
by
subtraction imaging technique, the influence of
calcification can be removed to determine whether it is really enhanced4,7. The diagnostic power of MRI
for complex cysts was higher than that of CT in our study. This was similar to
the previous research findings2-4,7. Because of the
superiority in soft tissue resolution of MRI, the potential of DWI to detect malignant
features, and enhanced MRI to avoid the effect of calcification, MRI may be more accurate and
favorable than CT in evaluating renal cystic masses.Conclusions
MRI
has high contrast resolution, functional imaging sequences such as DWI, lack of ionizing radiation, more sensitive
depiction of septa and wall nodules, better characterization of enhancement, and more precise imaging of inner structure and content of
the lesions.
MRI could be useful in improving the assessment of complex renal cysts.Acknowledgements
No acknowledgement found.References
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