Abstract: Objective To compare the ultrasonic morphological indexes of tibial neuropathy in patients with type 2 diabetes mellitus(T2DM), so as to seek the indexes with high diagnostic value in tibial neuropathy in patients with T2DM. 
Methods Sixty patients with T2DM who underwent lower extremity vascular ultrasound examination and tibial nerve ultrasound examination were reviewed. The patients were included or excluded based on various factors such as gender, age, course of disease, and so on. Subjects were divided into two groups(DPN group and non-DNP group) with 2 points as the diagnostic cut-off value by the Michigan Neuropathy Screening Instrument(MNSI) table. Two groups of data were compared, including width, thickness, cross-sectional area, mesh-like structure, and presence or absence of Doppler energy signal. 
Results There were no statistically significant differences in tibial nerve width, presence of clear mesh-like structure and presence of Doppler energy signal between two groups(P＞0.05). There were statistically significant differences in tibial nerve thickness and cross-sectional area between two groups(P＜0.05). The sensitivity and specificity of tibial nerve thickness(AUC=0.826) were 84.21% and 73.81% respectively, and positive and negative predictive values were 69.60% and 82.40% respectively. The sensitivity and specificity of cross-sectional area(AUC=0.921) were 94.74% and 85.71% respectively, and positive and negative predictive values were 81.80% and 94.40% respectively. The difference in ROC AUC between tibial nerve thickness and cross-sectional area was statistically significant(P=0.047). 
Conclusion The diagnostic value of tibial nerve thickness is medium in all ultrasonic features of tibial neuropathy in patients with T2DM, and when the cut-off value is 3.62 mm, the ideal efficacy can be obtained. The diagnostic value of cross-sectional area is relatively high, and when the cut-off value is 21.0 mm2, the ideal efficacy can be obtained.

Key words: diabetes mellitus, type 2, diabetic neuropathies, ultrasonography