Application value of contrast-enhanced ultrasound in the preoperative evaluation of renal cell carcinoma histological classification and RENAL score.

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Renal cell carcinoma (RCC), the most common malignant renal tumor, is primarily treated by surgical resection, including radical nephrectomy (RN) and partial nephrectomy (PN). At present, the choice of surgery mainly depends on the comprehensive evaluation of patients' clinical data, including histological classification, such as clear cell renal cell carcinoma (ccRCC) and non-clear cell renal cell carcinoma (nccRCC), and RENAL (radius, exophytic/endophytic, nearness, anterior/posterior, and location) score. Compared with biopsy and contrast-enhanced computed tomography (CECT), contrast-enhanced ultrasound (CEUS) is safer and less invasive. The purpose of this study was to assess the value of CEUS in the preoperative evaluation of histological classification and RENAL score of RCC. This retrospective study was conducted on a consecutive series of patients with renal tumors who underwent CEUS examination within 1 week prior to treatment at Lanzhou University Second Hospital between March 2021 and November 2023. The conventional ultrasound and CEUS features of RCCs were recorded and used to evaluate the RENAL score. Binary logistic regression was applied to analyze the independent risk factors of ccRCC. Diagnostic efficacy in evaluating ccRCC and nccRCC was compared between CEUS and CECT with the McNemar test. Among 246 patients, 248 RCCs were enrolled and were categorized into two groups: ccRCC (n=196) and nccRCC (n=52), with surgical pathology as the reference standard. The likelihood of hyperenhancement (P<0.001), heterogeneous enhancement (P<0.001), internal nonenhanced region ≤50% (P=0.001), and fast wash-in (P<0.001) in the ccRCC group was significantly higher than that in the nccRCC group, and these were independent risk factors of ccRCC. Moreover, the ccRCC group, as compared to the nccRCC, had a lower region of interest area of the largest range of tumor (Areamax) (P=0.045) and the difference between the local tumor and cortex in arrive time (∆ATtumor-cortex) (P=0.012) and shorter time to peak of the local tumor (TTPtumor) (P=0.022). The performance of CEUS in differentiating between ccRCC and nccRCC was comparable to that of CECT and showed high sensitivity (99.5%). Additionally, there was a significant difference in RENAL score based on the ultrasound features between the RN and PN group (P<0.001). The conventional ultrasound and CEUS features may help differentiate ccRCC from nccRCC and have significant potential in scoring the complexity prior to surgery, which could provide more precise and valuable information for diagnosis and treatment. CEUS has the capacity to optimize the treatment plan in a noninvasive manner and improve the prognosis of patients and should thus be further verified in multicenter, large-cohort, prospective research.