Objective: To assess the value of a microbubble-based ultrasonographic contrast agent for enhancing blood vessels in colour Doppler imaging (CDI) of small renal masses.
Patients and methods: Fifty-one patients with small renal masses (< 3 cm in diameter) had prospective CDI before and after intravenous administration of the contrast agent Levovist (Schering, Berlin, Germany). The degree of tumour vascularity was subjectively graded from 0 to IV (indicating an increasing vessel count). Furthermore, peak systolic velocity (PSV), resistive index, and pulsatility index were measured. The CDI findings were then compared with those obtained at histopathological examination.
Results: Intra- and/or peritumoral vessels were detected in 26 lesions (51%) by unenhanced CDI and in 48 by enhanced CDI (94%; P = 0.006, McNemar test). Higher grades of tumour vascularity (grade III and IV) were more common in malignant renal masses (P < 0.01). There were PSVs of >80 cm/s only in malignant lesions. Based on receiver operating characteristic analysis, enhanced CDI (area under the curve 0.789) was more accurate than unenhanced CDI (0.576) for differentiating benign from malignant renal masses (P < 0.004).
Conclusion: Enhanced CDI is better than unenhanced CDI for detecting tumour vascularity, and for discriminating between benign and malignant small renal masses.