The value of diffusion-weighted MRI in the diagnosis of malignant and benign urinary bladder lesions

Abstract

Objectives: To investigate the role of diffusion-weighted MRI (DWI) in the diagnosis of urinary bladder (UB) tumours by means of measuring apparent diffusion coefficient (ADC) values.

Methods: A total of 83 people aged between 18 and 86 years were included in the study: 63 patients with UB pathology (46 malignant, 17 benign) constituted the case group; 20 individuals without any UB pathology constituted the control group. DWI was applied to all individuals. The ADC values were measured based on the tissue of the UB mass entities and normal UB wall in the control group.

Results: The mean ADC value in the UB carcinoma group was significantly lower than that in the control group: 1.0684 ± 0.26 × 10(-3) mm(2) s(-1) and 2.010 ± 0.11 × 10(-3) mm(2) s(-1), respectively (p<0.01). There was a significant difference among the mean ADC values of different grades of malignant tumours, corresponding to 0.9185 ± 0.20 mm(2) s(-1) and 1.281 ± 0.18 mm(2) s(-1) in high-grade and low-grade malignant UB carcinomas, respectively (p<0.01). The ADC value in the carcinoma group was significantly lower than that in the benign lesion group: 1.0684 ± 0.26 × 10(-3) mm(2) s(-1) and 1.803 ± 0.19 × 10(-3) mm(2) s(-1), respectively (p<0.01). All 46 malignant lesions displayed a restriction in diffusion; 4 of the 17 benign lesions displayed a mild restriction in diffusion. The sensitivity, specificity and accuracy of DWI in the diagnosis of malignant UB lesions was 100%, 76.5% and 93.65%, respectively.

Conclusion: DWI can be beneficial in the differentiation of benign and malignant UB lesions, as well as of high-grade and low-grade UB carcinomas, using quantitative ADC measurements.

Figure 1

(a) Axial T₂ weighted MR image in a 64-year-old male depicting a 4 cm polypoid solid mass with a lobulated contour on the left lateral wall of the bladder. (b) On b = 1000 diffusion-weighted imaging, the mass shows a hyperintense signal corresponding to a restriction in diffusion. (c) Apparent diffusion coefficient (ADC) map of the same lesion. The ADC value of the lesion was measured as 1.27 × 10⁻³ mm² s^–1. Histopathologically, the lesion was reported as low-grade non-invasive urothelial carcinoma.

Figure 2

(a) Axial T₂ weighted MR image of a 76-year-old man depicting a 7 cm polypoid solid mass with a lobulated contour on the left wall of the bladder. (b) On b = 1000 diffusion-weighted imaging, the mass shows a hyperintense signal corresponding to a restriction in diffusion. (c) Apparent diffusion coefficient (ADC) map of the same lesion. The ADC value of the lesion was measured as 0.73 × 10⁻³ mm² s^–1. Histopathologically, the lesion was reported as high-grade invasive urothelial carcinoma.

Figure 3

(a) Axial T₂ weighted MR image in a 37-year-old female depicting a small polypoid solid mass with a lobulated contour on the left posterior wall of the bladder. (b) On b = 1000 diffusion-weighted imaging, the mass lesion on the left bladder wall does not show any restriction in diffusion. The apparent diffusion coefficient of the lesion was measured as 2.01 × 10⁻³ mm² s^–1. The histopathological result was polypoid cystitis.

Figure 4

(a) Axial T₂ weighted MR image in a 53-year-old male shows diffuse thickening of the bladder wall. (b) On b = 1000 diffusion-weighted imaging, the thickened bladder wall does not show any restriction in diffusion. (c) The apparent diffusion coefficient of the thickened bladder wall was measured as 1.64 × 10⁻³ mm² s^–1. The histopathological result was benign wall thickening.

Figure 5

(a) Apparent diffusion coefficient (ADC) distribution of the groups as a box plot. (b) Receiver operating characteristic (ROC) curve analysis. The cut-off value in the differentiation of malignant and benign bladder wall pathologies according to ADC values based on this curve is 1.545 × 10⁻³ mm² s^–1, with a sensitivity of 94.1% and specificity of 95.7%. (c) Cut-off value in the differentiation of high-grade and low-grade bladder carcinomas according to ADC values based on the ROC curve is 1.135 × 10⁻³ mm² s^–1, with a sensitivity of 78.9% and specificity of 85.2%.