Body Surface Gastric Mapping (BSGM): Is This the Future Standard of Care Noninvasive Test for Gastric Symptoms in Pediatrics?

There are several established diagnostic modalities to evaluate gastric function, including gastric emptying scintigraphy (GES) and antroduodenal manometry (AD manometry). However, they have several limitations. GES measures gastric emptying, but AD manometry is invasive, resource-intensive, not widely available, and its utility is far more useful in diagnosing pseudoobstruction than subtilties in gastric function [1, 2]. Breath testing is a newer test, so its role in predicting symptoms, its reproducibility, and the testing modifications needed for different pediatric populations is not known. Even MRI, barostat, and drink testing have been proposed as alternative methods for assessing gastric function. However, assessment of gastric function without robust correlation with symptoms is flawed as there are many variables that can affect testing results including medications, stress, and nutritional status. Therefore, there is an ongoing quest for non-invasive diagnostic tools that accurately describe gastric function and its relations to symptoms.

Body Surface Gastric Mapping (BSGM, Gastric Alimetry Auckland, New Zealand) is a new diagnostic device that uses high-resolution electrode arrays applied to the skin of the abdomen to record and spatially map gastric myoelectrical activity to define gastric electrophysiological phenotypes, correlate them with symptoms and symptom improvement with targeted therapies [3]. Compared with traditional electrogastrography (EGG), BSGM provides high-resolution spatial mapping and improved signalto-noise ratio and has filled a gap by making it possible to identify anomalies in slow-wave frequency, rhythm stability, and spatial propagation. Electrodes are placed over the epigastrium and signals from gastric slow waves are recorded continuously for pre and post a standardized meal for 4 h while symptoms are monitored on a mobile app to provide unique insights in addition to transit or pressure-based metrics alone [4].

Utilizing BSGM metrics (principal gastric frequency of 3 cycles/min, gastric Alimetry Rhythm Index (GA-RI), fasting and fed amplitude), different electrophysiologic phenotypes in functional dyspepsia (FD) that are not captured by symptom-based classification alone have been identified [4]. These phenotypes include [1]: rhythm instability phenotypes, characterized by reduced GA-RI indicating disorganized or dysrhythmic slow-wave activity [2]; abnormal frequency phenotypes, including bradygastria or tachygastria reflecting deviations from the normal ~3 cycles/min gastric rhythm [3]; low-amplitude phenotypes, suggestive of impaired neuromuscular function or reduced gastric electrical activity; and [4] impaired meal response phenotypes, defined by a blunted or absent postprandial increase in amplitude [3, 4]. Multimodal studies combining BSGM with imaging have demonstrated that gastric dysfunction is heterogeneous, with electrophysiological abnormalities not always correlating with delayed emptying [5]. BSGM can have wide diagnostic and therapeutic implications. In adults, it has been used to investigate symptoms such as chronic nausea, vomiting, early satiety, bloating and unexplained symptoms despite normal standard testing, diagnosis such as suspected FD, gastroparesis, chronic nausea and vomiting syndromes, post-fundoplication gastric dysfunction, and assess response to prokinetic therapy where lower amplitudes predicted reduced symptoms and lower rhythm stability predicted worse symptom burden [6–8].

Use of BSGM in children is emerging. Humphrey et al. have validated that BSGM can aid in the assessment and treatment of children with DGBI by identifying gastric electrophysiology patterns that correlate with symptom profile. BSGM findings contributed to clinical decision-making by differentiating patients with normal electrophysiology from those with rhythm instability, abnormal frequencies, or impaired meal responses [9, 10].

In another study of 32 healthy children 6–18years, BSGM spectral metrics were similar to those seen in healthy adults. The key distinction was reduced gastric rhythm stability in the later phases of the post-prandial period [9]. Similarly, a prospective study of 25 adolescents with FD or gastroparesis and 30 healthy controls ages 12–20years has identified distinct BSGM phenotypes differentiating these groups. However, no discernible differences were noted between BSGM measures in children with gastroparesis compared to those with FD [10].

While this new technology has appeal because it is non-invasive [11], there are significant logistic challenges to use in pediatric hospitals. First, the current electrode array is large, making this test only viable for larger children. Second, children need to be able to stay still for 4.5 h which can be difficult. Third, the arrays are expensive and insurance approval is not widespread. Fourth, given the long length of this test, finding a location and staff available to perform and monitor patients for this test is challenging, particularly in urban hospitals where space is at a premium. Fifth, many children have significant medical complexities with pacemakers, enteral tubes, and ostomies, making the placement of these whole-abdomen arrays challenging. Moreover, there is significant hesitation to perform tests without evidence that the results predict clinically meaningful outcomes. So, as of yet, gastric scintigraphy still remains the most clinically relevant test for gastric function. If data becomes available showing that patients with a particular BSGM profile respond consistently to a therapy, there may be more excitement about testing in children. Finally, all of the studies using this technology are from the same pediatric centers largely from New Zealand, so determining the reproducibility and generalizability outside of these two centers will be critical. This new technology is exciting because it is non-invasive and well tolerated in older patients. However, data is needed to determine how this technology predicts outcomes more effectively than either scintigraphy or AD manometry. Since this device is non-invasive and well tolerated with minimal risks of mild skin irritation from electrodes, it could easily be incorporated in the clinical setting.

To bring this into routine pediatric clinical practice, additional technological modifications will greatly enhance the excitement of this technology. Smaller arrays and shorter recording times with associated validation of these method modifications will be critical for success in children. For this reason, the main indication for use at this time may be for teenagers with persistent symptoms who are unable to complete GES or AD manometry; though, at this time, this is a very small population. Humphrey et al. have already published pediatric norms, which is the first step towards getting normative data in this population [4].

Further studies should evaluate the additive investigative effects with gastric scintigraphy/AD manometry as well as the predictive value of BSGM for treatment outcomes before widespread use in this population.

Data Availability Statement

Data sharing not applicable to this article as no datasets were generated or analysed during the current study.