Gastric mapping is a specialized diagnostic test used to assess the neuromuscular function of the stomach. The procedure focuses on measuring the electrical activity and resulting muscle contractions that regulate digestion. This testing provides medical professionals with insight into how effectively the stomach moves its contents into the small intestine. It is a tool for diagnosing motility disorders when standard tests have not provided a clear explanation for persistent digestive symptoms. By recording the stomach’s electrical signals, the map helps determine if a functional problem is causing the patient’s distress.
Defining the Purpose of Gastric Mapping
The primary purpose of gastric mapping is to visualize the stomach’s electrical rhythm, often called the slow wave. This electrical pacemaker activity originates in specialized cells within the stomach wall, dictating the frequency and coordination of muscle contractions. In a healthy person, the electrical signals occur at a regular rate, typically around three cycles per minute. The rhythmic electrical activity triggers the muscular contractions, or peristalsis, that propel food through the digestive tract.
Gastric electrical mapping, or electrogastrography (EGG), works like an electrocardiogram (EKG). Electrodes placed on the skin over the abdomen record the weak electrical signals generated by the stomach muscles. This method helps differentiate between normal, coordinated electrical patterns and abnormal, disorganized rhythms, known as gastric dysrhythmias. The resulting map provides a functional blueprint of the stomach’s movement patterns, which is unobtainable through static imaging tests.
Conditions That Require Gastric Mapping
Gastric mapping is typically ordered when a patient experiences chronic, unexplained symptoms that suggest a problem with stomach emptying or function. Indications include persistent nausea, recurrent vomiting, and abdominal discomfort that cannot be attributed to a physical obstruction or ulcer. It is an important step in the diagnosis or management of gastroparesis, a disorder characterized by delayed stomach emptying.
This diagnostic tool helps confirm if the delayed emptying is related to abnormal electrical control rather than a physical impediment. It is also used to evaluate refractory functional dyspepsia, which involves persistent upper abdominal pain or discomfort without an identifiable organic cause. By investigating the underlying electrical control, the test can help determine if a motility issue is contributing to the patient’s symptoms, guiding subsequent treatment strategies. The test can also evaluate the effectiveness of certain medications designed to enhance stomach motility.
The Procedure and Patient Preparation
Non-invasive gastric mapping, often called Electrogastrography (EGG) or Body Surface Gastric Mapping (BSGM), generally takes between one and three hours to complete. Several electrodes are placed on the skin of the abdomen over the area corresponding to the stomach, often after the skin is cleaned or lightly abraded to improve signal quality.
Patient preparation prevents interference with the electrical recording. Patients are required to fast for at least six hours before the test to ensure the stomach is empty for a baseline recording. Individuals must temporarily discontinue certain medications that affect gastric motility, such as prokinetics, anti-emetics, or opioid pain relievers, typically 48 to 72 hours prior to the appointment.
The procedure begins with a baseline recording period of 30 to 60 minutes while the patient is fasting and resting quietly. Following the baseline, the patient consumes a standardized test meal to stimulate the stomach’s digestive activity. The electrical recording continues for one to two hours after the meal to capture the stomach’s response to food intake. Throughout the test, the patient is asked to remain still to minimize movement artifacts that could interfere with the electrical signal recording.
Interpreting the Mapping Results
The data is analyzed to generate spectral graphs illustrating the stomach’s electrical frequency and power. Physicians look for both frequency abnormalities and the post-meal response to determine the nature of the motility problem. A normal result shows a consistent three-cycle-per-minute rhythm and a noticeable increase in electrical power after the test meal is consumed.
Abnormal readings can be categorized as a type of gastric dysrhythmia, indicating a functional problem with the stomach’s electrical pacemaker. Tachyarrhythmias, or tachygastria, occur when the electrical frequency is too fast, while bradyarrhythmias, or bradygastria, describe an electrical frequency that is too slow. A weakened or absent increase in electrical power after the meal suggests that the stomach muscle is not responding appropriately to the stimulus of food. The results provide objective functional information that, when combined with the patient’s symptoms and other diagnostic data, helps confirm the presence of a gastric motility disorder.