Role of antibiotic use and the superb microvascular imaging (SMI) method in lymphadenitis

Objective: This study aims to investigate whether Superb Microvascular Imaging (SMI) as an adjunct to B-mode ultrasonography (US) can contribute to differentiating benign lymph nodes, assessing the change in lymphadenitis after antibiotic use, and its role in the diagnosis and follow-up of lymphadenitis. Materials and Methods: Between April 2024 and March 2025, 17 patients, 65 lymph nodes, who underwent cervical lymph node ultrasonography at the Radiology Department of Celal Bayar University, were included in the study. In grayscale US examination, the largest diameter of the lymph nodes, the short-to-long diameter ratio, cortical thickness, shape of the lymph node, presence of fatty hilus, and whether the shape was lobulated or not were assessed. Then, in the SMI examination, the boundaries of the lymph node were marked manually, and the vascularity index was automatically calculated by the device. Additionally, the vascularity index determined by the Power Doppler and ADF examinations was assessed. In these Doppler examinations, a 5-point scoring system and Adler classification were performed with joint consensus of two radiologists, evaluating the number of vascular vessels. The study examined lymph nodes secondary to viral and bacterial infections. The grayscale US and vascularity index (VI) values obtained were statistically analyzed to assess their diagnostic value. Results: In the lymph nodes included in the study, grayscale US evaluation showed a statistically significant increase in cortical thickness and short-to-long diameter ratio before and after antibiotic use (10 days) in benign lymph nodes (p<0,05). In the SMI examination, the average and median VI values measured before antibiotic use were found to be significantly higher compared to those measured after antibiotic use (p<0,05). According to the threshold analysis, when the Power Doppler vascular index was ≥5,75, sensitivity was found to be 60,0% and specificity 78,5%. In the threshold analysis, when the cSMI vascular index was ≥4,65, sensitivity was 55,4% and specificity 58,5%. In the threshold analysis, when the mSMI vascular index was ≥2,25, sensitivity was 84,6% and specificity 30,8%. According to the threshold analysis, when the ADF vascular index was ≥3,45, sensitivity was 64,6% and specificity 60,0%. Conclusion: Our research showed that when the new Doppler method, SMI, is evaluated together with grayscale US findings, it can be diagnostically valuable in monitoring treatment and assessing lymphadenitis findings after antibiotic use. Additionally, evaluating the regression of benign lymph nodes with suspicious malignant US findings after antibiotic treatment was meaningfully considered to avoid unnecessary invasive procedures. Keywords: Lymph node, SMI, Ultrasound