Application value of transrectal contrast-enhanced ultrasound combined with magnetic resonance imaging in T staging and treatment decision-making for middle and low rectal cancer

Objective To explore the application value of contrast-enhanced ultrasound (CEUS) combined with magnetic resonance imaging (MRI) in T staging of middle and low rectal cancer, providing an accurate basis for multidisciplinary treatment (MDT). Method AA retrospective analysis was conducted on the case data of 80 consecutive patients with middle and low rectal cancer admitted to the hospital from April 2023 to February 2025. All patients underwent transrectal ultrasound (TRUS), CEUS, and 3.0T MRI examinations within one week before biopsy or surgery. Using postoperative pathological results as the gold standard, the diagnostic performance of single and combined examinations in diagno-sing T staging of low rectal cancer was calculated separately. Result The combined examination for T1 rectal cancer showed a sensitivity of 87.5%, specificity of 99%, positive predictive value of 99.9%, and negative predictive value of 96.7%. For T2 rectal cancer, the sensitivity, specificity, positive predictive value, and negative predictive value were 91.3%, 96.3%, 91.3%, and 96.3%, respectively. For T3 rectal cancer, these values were 93.5%, 97.8%, 96.7%, and 95.7%, respectively. For T4 rectal cancer, these values were 90%, 98.5%, 90%, and 98.5%, respectively. The diagnostic accuracy of the combined examination for T1-T4 rectal cancer was 97.5%, 97.5%, 96.25%, and 98.7%, respectively. The diagnostic accuracy of CEUS examination alone for T1-T4 stages was 87.5%, 86.96%, 80.65%, and 80%, respectively. The diagnostic accuracy of MRI examination alone for T1-T4 stages was 81.25%, 78.26%, 90.32%, and 90%, respectively. The accuracy of the combined examination was significantly higher than that of CEUS or MRI examination alone (P<0.05). The consistency between the combined examination and pathological staging was good (Kappa value=0.877, P<0.05). After CEUS combined with MRI examination, the area under the curve (AUC) of the receiver operating characteristic curve of the diagnostic model rose to 0.85, significantly exceeding that of single examination methods(CEUS AUC=0.75, MRI AUC=0.758). Additionally, it was found that T1-T2 rectal cancer showed varying degrees of uniform enhancement on CEUS, and the specificity of CEUS combined with MRI in diagnosing T1-T2 rectal cancer reached over 96.3%. The low enhancement observed on CEUS in the portal phase achieved a high specificity of 95.5% for diagnosing T3 and higher-stage tumors. Conclusion CEUS combined with MRI has significant advantages in the diagnosis of T staging of rectal cancer, especially for T1 and T2 stages, which have notable superiority over single examination. The accuracy of the combined examination can reach 97.5% and 97.5%, and the specificity can reach 99% and 96.3%, respectively, making it useful for ruling out non-neoplastic lesions.