2453. Contrast Enhanced Ultrasound for Renal Cystic Lesions: An Algorithmic Approach
Authors * Denotes Presenting Author
  1. Blake Sarrazin; University of Missouri School of Medicine
  2. Nanda Thimmappa *; University of Missouri School of Medicine
Renal Contrast Enhanced Ultrasound (CEUS) is an effective modality for identifying features concerning for malignancy in complex cystic lesions and is therefore an immensely beneficial problem-solving tool for select patients. However, CEUS requires a coordinated effort between a radiologist, sonographer, and IV team and thus demands more time and effort than some other imaging modalities. Additionally, not all cystic lesions will benefit from CEUS and hence there is a need to determine which characteristics distinguish these lesions. In this study, we review the features of various cystic lesions on conventional US, CT, and MRI studies and compare them with CEUS appearance in order to develop an algorithm to better identify the subset of cases that will benefit most from CEUS.

Materials and Methods:
CEUS (Lumason contrast agent) studies performed on 46 patients with 53 cystic lesions were retrospectively identified from March 2019 to June 2020 and included in this analysis. Indication for these studies were ‘complex’ cystic features described on US, CT or MRI. We looked at imaging features on studies leading up to CEUS [presence or absence of septa, appearance of the septations, solid enhancing nodules within the cyst] and CEUS enhancement patterns [no flow of microbubbles, occasional bubbles, constant flow, or solid nodules]. Conventional sonographic and CEUS appearances of the cystic lesions were evaluated to identify pre-contrast features that favor malignancy vs. benignity and thus warrant further assessment by CEUS vs. discontinuation of imaging work-up.

53 cystic renal masses were evaluated by conventional US and CEUS. 21 had thin internal septations, 100% of these lesions showed no/occasional bubbles (benign) on CEUS. 12 had thick internal septations, of these, 67% showed constant flow (malignant). 11 showed echogenic debris, of which 82% showed no bubbles (favoring hemorrhagic cysts) while 2 larger lesions showed solid enhancing nodules. 9 lesions were simple cysts with no enhancement.

Overall, identifying appropriate indications for CEUS in the work-up of cystic renal lesions can greatly improve CEUS workflow. Our preliminary data show that indications for CEUS should be thick (>1mm) and/or irregular internal septations, questionable solid nodules, echogenic cysts >1cm, or suboptimal image quality on US, CT, or MRI. It appears that there is no benefit in performing CEUS on lesions with thin internal septa, anechoic cysts, or small cysts of <1cm as they are too difficult to visualize and accurately characterize.