Value of High Frame Rate Contrast-Enhanced Ultrasound in Evaluating Vascular Morphology of Renal Cell Carcinoma

Different subtypes of Renal Cell Carcinoma (RCC) exhibit distinct tumor vascular morphological features. However, current imaging techniques still have limitations in delineating the vascular morphology of RCC.

The study aims to evaluate the value of high-frame-rate contrast-enhanced ultrasound (H-CEUS) in assessing the vascular morphology of RCC.

A retrospective analysis was conducted on 163 RCC patients who were classified postoperatively into clear cell RCC (ccRCC) and non-clear cell RCC (nccRCC) groups. All patients underwent conventional US, conventional CEUS (C-CEUS), and H-CEUS preoperatively. Vascular morphology during the early phase of CEUS perfusion was categorized into five types (I-V). Differences in vascular morphology were compared using the χ2 test or Fisher's exact test, and inter-observer agreement was evaluated using the Kappa coefficient.

A significant difference in CDFI was observed between the ccRCC and nccRCC groups (χ2=11.755, P = 0.0088). In C-CEUS and H-CEUS, type III vascular morphology was most common in ccRCC. The proportion was significantly higher in H-CEUS than in C-CEUS (62.6% vs. 45.8%; χ2=6.099, P = 0.014). Type IV was the most common vascular morphology in nccRCC, with no significant difference between C-CEUS (58.9%) and H-CEUS (44.6%) (χ2=2.289, P = 0.130). H-CEUS revealed significant vascular morphological differences in ccRCC ≤4 cm (χ2=9.307, P = 0.038), but not in nccRCC ≤4 cm or in any tumors >4 cm. Inter-observer agreement for vascular morphology evaluation was substantial for both CCEUS (κ=0.751) and H-CEUS (κ=0.657) (both P<0.001).

H-CEUS offers superior visualization of vascular morphology in ccRCC lesions ≤4 cm, providing valuable insights into its potential as a noninvasive imaging modality for differentiating RCC subtypes and tailoring treatment strategies.