Importance Persistent upper gastroduodenal symptoms, such as nausea, vomiting, bloating, and abdominal pain, are widespread among pediatric patients. Multiple overlapping symptoms complicate the diagnostic process, necessitating the development of novel gastric function tests with actionable biomarkers. Body Surface Gastric Mapping (BSGM) has emerged as a promising diagnostic tool for gastroduodenal disorders, and this is the first detailed evaluation in adolescents. Objective This study aimed to assess the utility of BSGM in delineating specific patient phenotypes among adolescents with functional dyspepsia (FD) and gastroparesis in order to guide clinical decision-making. Design A prospective cross-sectional study recruited adolescents aged 12 to 21 between 2022 and 2024. Setting Controls were recruited from New Zealand (controls) and Patients from the Children's Hospital of Philadelphia, Pennsylvania, USA. Participants Prospectively recruited participants included controls without gastroduodenal symptoms or motility-related medication usage and patients diagnosed with either gastroparesis (delayed gastric emptying test (GET)) or FD according to ROME IV criteria and a normal GET. Procedures BSGM was performed using a standardized protocol, including simultaneous symptom reporting and the completion of validated symptom, psychometric and physical health questionnaires. Main Outcome The primary outcome was to evaluate if BSGM could delineate specific patient phenotypes and provide clinically meaningful distinctions between gastroparesis and FD diagnoses, utilizing BSGM spectral outcome data. Results Fifty-six subjects were recruited (31 controls, 25 patients); median age 16; 96% of patients were female. Control data showed that adult reference intervals provided an acceptable interpretation framework. Patients with FD (n=10) and gastroparesis (n=15) had common symptoms, mental health, quality of life and functional disability (all p>0.05). Three distinct BSGM phenotypes were identified: BSGM Normal (n=10), BSGM Delay (n=8), and Low Stability/Low Amplitude (n=7), having spectral differences in BMI-Adjusted Amplitude 34.6 vs 39.1 vs 19.9 (p=.01) and Gastric Alimetry Rhythm Index: 0.45 vs 0.45 vs 0.19 (p=.003). BSGM phenotypes demonstrated differences in symptoms (nausea p=0.04), physical health (p=.04) and psychometrics (anxiety p=.03). Conclusion and Relevance Adolescent patients with FD and gastroparesis have overlapping clinical profiles, making individualized treatment challenging. Conversely, employing BSGM to categorize patients into distinct phenotypes revealed clinically relevant differences, offering potential avenues for individualized therapeutic pathways.

GOG and AG hold grants and intellectual property in gastrointestinal electrophysiology. GS, SC, GOG, AG, and CNA are Alimetry's shareholders and employees. GOG is a Director at The Insides Company. The remaining authors have no conflicts of interest to declare.

This research has been supported by the New Zealand Health Research Council, New Zealand and the Children's Hospital of Philadelphia, Pennsylvania, USA.

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The Ethics Committee of the New Zealand Health and Disability Ethics Committee and the Ethics Committee/IRB of the Childrens Hospital of Philadelphia USA gave ethical approval for this work

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