Comparison of Fasting Gastric Volume in different Phases of Menstrual Cycle and Correlation with Hormonal Levels: A Prospective Observational Study Protocol

Pulmonary aspiration remains a serious perioperative complication, particularly in patients with full stomachs. Gastric ultrasonography (USG) serves as a reliable, non-invasive bedside tool to estimate gastric volume and contents, helping assess aspiration risk. Existing research indicates that gastric emptying and motility may be influenced by hormonal changes during different phases of the menstrual cycle, mediated through oestrogen and progesterone effects on smooth muscle tone and nitric oxide synthase pathways. However, the literature presents conflicting findings—some studies report faster gastric emptying in the luteal phase, while others document delayed emptying. Given this inconsistency, the proposed study aims to evaluate the effect of menstrual cycle phase (follicular vs. luteal) on fasting gastric volume in healthy female subjects using point-of-care gastric ultrasonography. The goal is to determine whether hormonal variations across the cycle have clinically relevant implications for preoperative fasting guidelines and aspiration risk assessment in women.