To evaluate the accuracy of double contrast-enhanced ultrasonography (DCUS) and endoscopic ultrasonography (EUS) in the preoperative N staging of gastric cancer.

Between June 2015 and September 2016, a total of 65 consecutive patients who were diagnosed with histologically confirmed gastric carcinoma and underwent surgery in the 2^nd Affiliated Hospital of Wenzhou Medical University were enrolled into this study. DCUS and EUS were performed in all patients to estimate lymph node metastasis (N stage) within 5 days before surgery. The findings of the histopathologic examination of resected specimens were considered as gold standard and were retrospectively compared with the results of DCUS and EUS. The sensitivity, specificity and Youden index of DCUS and EUS were calculated. The difference of diagnostic performance between DCUS and EUS was assessed by chi-square test.

There were 25 N- patients and 40 N+ patients confirmed by pathology. Of all 25 N- cases, 18 cases were diagnosed correctly by DCUS and 20 cases were diagnosed correctly by EUS; Of all 40 N+ cases, 32 cases were diagnosed correctly by DCUS and 31 cases were diagnosed correctly by EUS. The sensitivity, specificity and Youden index of DCUS were 80.0%, 72.0% and 0.52 respectively. The sensitivity, specificity and Youden index of EUS were 77.5%, 80.0% and 0.58 respectively. The overall accuracy of DCUS and EUS in N-staging were 76.9% (50/65) and 78.5% (51/65). There was no significant difference between two methods (χ²=0.044, P=0.833).

There was no significant difference between DCUS and EUS in overall N-staging of gastric cancers. Either of these two methods had its advantages and disadvantages. When the two methods were combined, the accuracy of preoperative N-staging of gastric cancers could be improved and this improvement may influence treatment algorithms.