Contrast-enhanced ultrasound manifestations of renal masses undetectable on conventional ultrasound

Abstract

This study aimed to retrospectively analyze the features of contrast-enhanced ultrasound (CEUS) of renal masses that cannot be detected by conventional ultrasound (CUS). The data of 264 patients who underwent CEUS for renal lesions from January 2016 to December 2019 were retrieved. Of these, 16 patients with renal masses which were not detected by CUS were included in the final analysis. The corresponding characteristics of CEUS were evaluated, including intensity of enhancement, homogeneity, wash-in and wash-out patterns, and perilesional rim-like enhancement. Of the 16 patients, 10 patients had clear cell renal cell carcinoma (ccRCC) and 6 patients had urothelial carcinoma of the renal pelvis (UCRP). Compared with the location on non-enhanced computed tomography (CT) scan, all tumors were detected on CEUS. Most (7/10) of the ccRCCs appeared as hyperenhancement, homogeneous enhancement, synchronous-in, and no perilesional rim-like enhancement. Most (4/6) of the UCRPs appeared as isoenhancement, slow-in, fast-out, and no perilesional rim-like enhancement. CEUS may be helpful in the diagnosis and differential diagnosis of renal tumors which were not observed on CUS, and it might be an alternative method for some patients when contrast-enhanced computed tomography (CECT) or magnetic resonance imaging (MRI) cannot be performed.

Contrast-Enhanced Ultrasound in the Diagnosis of Solid Renal Lesions

“…The results of studies conducted in the recent past have confirmed that the presence of a pseudo-capsule, rapid wash-out, and high and heterogeneous enhancement on CEUS examination indicate the malignant nature of the lesion and most often indicate a diagnosis of renal cell carcinoma [19,22,24]. In contrast, benign lesions usually show slow centripetal enhancement, homogeneous peak enhancement, and gradual wash-out [19,24].…”

“…This examination is performed using a microbubble contrast agent that is not nephrotoxic. CEUS is performed especially in patients with chronic renal failure or allergy to contrast agents used in other imaging modalities such as CT or MRI [22,23].…”

“…In studies conducted by various researchers, different parameters have been considered in the evaluation of solid lesions during CEUS examination. These include enhancement of the lesion compared to surrounding healthy renal parenchyma, homogeneous or heterogeneous wash-in, and the presence or absence of a pseudo-capsule, defined as rim enhancement [22,24].…”