Role of Low-Mechanical Index CEUS in the Differentiation between Low and High Grade Bladder Carcinoma: a Pilot Study

Purpose: To assess the efficacy of low-mechanical index contrast-enhanced ultrasonography (CEUS) in the differentiation of a series of histologically proven bladder lesions identified via conventional cystoscopy and biopsied. Materials and Methods: 36 patients (mean age: 62 years; range 45 - 72 years) with bladder lesions previously detected by color power Doppler ultrasonography (CDUS) were prospectively examined with low-mechanical index contrast-enhanced US after bolus administration of 2.4 ml of Sonovue (Bracco, Milan, Italy). All lesions were evaluated in real-time continuous scanning for 2 minutes and the videos were registered. Two ultrasound (US) experts evaluated the videos by consensus and assigned a score to the enhancement pattern. Subsequently, a specific sonographic quantification software (Qontrast, Bracco, Milan, Italy) based on pixel by pixel signal intensity over time was used to obtain contrast-enhanced sonographic perfusion maps for each lesion. Time-intensity curves (TICs) of each lesion were then extracted from the region of interest positioned within the lesion and in the closest bladder wall. The sensitivity and specificity of CDUS and CEUS were compared using McNemar's test. All patients subsequently underwent conventional cystoscopy with biopsy or transurethral resection. Results: 22 high-grade and 14 low-grade transitional cell carcinomas (TCCs) were histologically diagnosed (mean diameter 2.1 cm; range: 1 - 4.5 cm). The sensitivity and specificity of CDUS were 86.4% (19/22; 95% CI = 66.7 - 95.3%) and 42.9% (6/14; 95% CI = 21.4 - 67.4%), respectively. The sensitivity and specificity of CEUS were 90.9% (20/22; 95% CI = 72.2 - 97.5%) and 85.7% (12/14; 95% CI = 60.1 - 95.9%), respectively. The sensitivity and specificity of CEUS using TICs were 95.4% (21/22; 95% CI = 78.2 - 99.2%) and 85.7% (12/14; 95% CI = 60.1 - 95.9%), respectively. There was no significant difference between the sensitivity of CDUS versus CEUS, CDUS versus TIC, and CEUS versus TIC (p > 0.05; McNemar's test). The specificity of CEUS and TIC was significantly higher than that of CDUS (p < 0.05; McNemar test). Conclusion: CEUS is a reliable noninvasive method for differentiating low-and high-grade bladder carcinomas since it provides typical enhancement patterns as well as specific contrast-sonographic perfusion curves. However, further studies involving larger patient populations is mandatory to confirm these promising results.