Gastric Emptying After a Yoghurt Breakfast in Children: a Pilot Study

Background and rationale

Preoperative fasting in children aims to reduce residual gastric contents while avoiding the adverse effects of unnecessarily prolonged restriction of oral intake. Hunger, thirst, discomfort and metabolic disturbances provide a rationale for investigating shorter fasting intervals. European paediatric fasting recommendations have increasingly supported shorter intervals for clear fluids and breast milk. These developments do not establish an appropriate fasting interval for semi-solid foods, whose emptying may depend on the amount ingested, energy density and nutrient composition.

Yoghurt is a familiar food for children and a potential component of a light preoperative breakfast. Its semi-solid structure and macronutrient content distinguish it from clear fluids. Previous paediatric studies of light breakfasts, including yoghurt or gruel, have reported low residual gastric volumes in most children after approximately four hours, while also showing variability in gastric emptying. Whether a three-hour interval is sufficient after yoghurt intake remains uncertain. Upper gastrointestinal endoscopy provides an opportunity to assess intragastric contents directly alongside ultrasound findings.

Primary objective and hypothesis

The primary objective is to compare gastric emptying after three versus four hours of fasting following a yoghurt breakfast. This comparison will be evaluated using the proportion of children meeting the ultrasound empty-stomach criterion at the first assessment at their allocated fasting interval. The primary hypothesis is that the three-hour group will have a similar proportion of empty stomachs to the four-hour group. Similarity is a research hypothesis; no formal equivalence or non-inferiority margin has been specified.

Secondary objectives

Secondary objectives are to compare ultrasound-estimated gastric volume, endoscopic findings and hunger between the randomized groups, and to assess agreement between gastric ultrasonography and endoscopic assessment. Method agreement is a secondary analysis and does not determine the primary comparison of the two fasting intervals.

Design and setting

This is a prospective, single-centre, randomized, parallel-group pilot study at Baskent University Faculty of Medicine Ankara Hospital, Ankara, Turkey. Twenty-four children will be allocated in a 1:1 ratio to a three-hour or four-hour fasting group, with 12 participants per group. Planned study dates are 7 to 19 October 2026. Ahmed Uslu is the principal investigator. Ethics approval has been reported.

Participants and consent

Children aged 1 to 10 years, of either sex, with American Society of Anesthesiologists physical status I or II and scheduled for elective upper gastrointestinal endoscopy under anaesthesia will be eligible. Children with cardiac, respiratory or peripheral circulatory disorders, diabetes mellitus, or a condition that delays gastrointestinal transit will be excluded. Families will receive detailed information about the study, with age-appropriate information for children, and written informed consent will be obtained from a parent or legal guardian before enrollment. Preprocedure assessment and investigations will follow the hospital's usual practice.

Yoghurt intake and group allocation

Both groups will be permitted ad libitum yoghurt intake up to a maximum of 150 g. No fixed dose or weight-based quantity will be prescribed. The actual amount consumed will be recorded in grams. The randomized comparison concerns the planned interval between yoghurt ingestion and the first gastric ultrasound assessment: three hours in one group and four hours in the other. Actual fasting duration, the time of last water intake, body weight, age, and the times of ultrasound and endoscopy will be recorded. These records will describe variation in intake and the achieved assessment intervals.

Masking

The clinicians performing gastric ultrasonography and upper gastrointestinal endoscopy will be blinded to randomized fasting-group allocation. The anaesthetist will know the assigned group and oversee the timing of anaesthesia and the procedure. Masking refers to the outcome assessors; it does not mean that two different assessment procedures constitute two separate categories of masking.

Gastric ultrasound and procedural sequence

Standard monitoring will include electrocardiography, non-invasive blood pressure and pulse oximetry. Gastric ultrasonography will be performed before anaesthetic induction, with the child in the right lateral decubitus position. Two orthogonal antral diameters will be measured in triplicate. Antral cross-sectional area will be calculated using the ellipse formula, CSA = pi x A x B / 4, with diameters expressed in millimetres and area in square millimetres. The planned gastric volume estimate is GCV (mL/kg) = 0.0093 x CSA (mm2) - 0.96. This equation provides a weight-indexed volume, rather than an absolute volume in mL.

The supplied project summary defines an ultrasound volume below 1.5 mL/kg as meeting the empty-stomach criterion. If this criterion is not met, ultrasound assessment will be repeated at 10-minute intervals and anaesthesia will be deferred until the protocol criterion is met. The case report form contains fields for the first examination and two repeat examinations. The first examination at the allocated fasting interval will remain the basis of the primary outcome, regardless of subsequent emptying.

Anaesthesia and endoscopy

Anaesthetic management will follow the institution's clinical practice. During upper gastrointestinal endoscopy, the gastroenterologist will document the nature and quantity of residual gastric contents. Ultrasound and endoscopy times will be retained so that any interval between the two assessments is identifiable. The clinically indicated endoscopic procedure and routine recovery care will otherwise proceed according to usual practice.

Outcomes and interpretation

The first ultrasound assessment addresses the randomized three-hour versus four-hour comparison. Endoscopic observations occur after the ultrasound-guided decision to proceed and may therefore follow a longer interval in children requiring repeat scans. Agreement analyses will be interpreted in this procedural context. Direct endoscopic observations provide complementary information about residual contents; they do not independently establish the safety of the assigned fasting interval against rare pulmonary aspiration events.