This is a prospective cohort study. The main objective is to compare the prevalence of a "full stomach" using gastric ultrasound technique, in elective surgical patients with diabetes mellitus compared to non-diabetic controls following the present fasting guidelines (2 h after clear liquid and 6h after a light meal). For patients with a full stomach or intermediate stomach, an consecutive ultrasound scan is performed every 10 min,until empty stomachstomach contents are detected to determine the mean gastric emptying time for clear liquid and light meal, and to investigate the risk factors for delayed stomach emptying in diabetic patients by logistic regression analysis .

Inclusion Criteria:

• diabetes (two fasting plasma glucose concentration≥7mmol/L or casual plasma glucose concentration≥11.1mmol/L);
• age≥18 yr; ASA physical status I-III;
• body mass index <35kg/m2;
• who are admitted to the surgical department;
• who are able to understand the rationale of the study and provide informed consent.

Exclusion Criteria:

• pregnancy;
• a history of upper gastrointestinal disease or previous surgery on the oesophagus, stomach or upper abdomen;
• documented abnormalities of the upper gastrointestinal tract such as gastric tumors;
• recent upper gastrointestinal bleeding (within the preceding 1 month);
• taking medicines that may delay gastric emptying(e.g., anticholinergic agents).
• hypothyroidism.

Study participants will be diabetic and non-diabetic patients who are admitted to the surgical department and scheduled to undergo elective surgical procedures. 100 participants will be recruited in total.