• HRV or the magnitude of power in the LF or HF in the fasting or post-prandial state [ Time Frame: Same day ] [ Designated as safety issue: No ]
• HRV or stress profile parameters following an acute stress(mental math) [ Time Frame: Same day ] [ Designated as safety issue: No ]
• Frequency of an abnormal EGG or the magnitude of EGG parameters [ Time Frame: Same day ] [ Designated as safety issue: No ]
• Water load volume [ Time Frame: Same day ] [ Designated as safety issue: No ]

• Behavioral Assessment System for Children (BASC) [ Time Frame: Same day ] [ Designated as safety issue: No ]
• Salivary cortisol [ Time Frame: Same day ] [ Designated as safety issue: No ]
• A stress profile via the biofeedback equipment (e.g. measures of muscle tension, hand temperature, and skin moisture (conductance). [ Time Frame: Same day ] [ Designated as safety issue: No ]

The current study is designed to assess relationships between anxiety/stress, autonomic nervous system balance, and electrical activity in the stomach before and after eating/drinking in children with abdominal pain.

Chronic or recurrent abdominal pain in children is a very common complaint in children and adolescents, and is most often associated with the presence of a functional gastrointestinal disorder (FGID). It is likely that the clinical symptoms in FGIDs are the result of an interaction between biologic, psychologic, and social factors. The psychologic factor most implicated is chronic stress or anxiety. Stress may influence gastrointestinal function and symptoms through altering the balance of the autonomic nervous system (ANS). Imbalance in the ANS has potential effects on gastrointestinal mechanosensitivity, motor function (e.g. stomach emptying and accommodation), and electrical rhythms. All of these can be associated with abdominal pain. Theory and early evidence from studies done with healthy adult populations suggest that ANS imbalance can reduce the body's ability to respond electrically to food/water consumption. However, the relationships between chronic stress/anxiety, ANS balance/imbalance, and electrical activity in the stomach before and after eating/drinking remain to be fully explored in children with FGIDs. The current study is a two-part pilot study designed to assess these relationships. Part I involves assessment of anxiety/stress (i.e., BASC parent- and self-reports) along with ANS balance (i.e., heart rate variability) and electrical activity in the stomach (i.e., electrogastrography) measured in the fasting state and following a test meal. Part II involves the same assessments with rapid water loading replacing the test meal. Results will be analyzed by specific FGID, as well as for the group as a whole. We expect to enroll 75 children ages 8-17 in each part, including 30 healthy controls and 45 children with an FGID. Elucidating these relationships is a necessary first step in developing more effective treatments for children with recurrent abdominal pain and, ultimately, reducing the personal and societal costs of this common pain entity.

• Children with FD
• Children with IBS
• Children with FD and IBS
• Healthy controls

Inclusion Criteria:

• Ages 8 - 17 years
• Evaluated in Abdominal Pain Clinic at Children's Mercy Hospital or the Gastroenterology Clinic at Children's Mercy South for abdominal pain of at least 8 weeks duration and fulfilling symptom-based criteria for FD, IBS, or FD/IBS.

Exclusion Criteria:

• Previous abdominal surgery
• Chronic disease requiring regular medical care (e.g. gastrointestinal diseases, diabetes mellitus, juvenile rheumatoid arthritis, cystic fibrosis, cancer).
• Non-English speaking

NOTE: Control subjects will meet all patient inclusion/exclusion criteria except for Inclusion Criteria #2. Control subjects will be excluded for history of abdominal pain, nausea, vomiting, diarrhea, constipation, or bloating.