Cutaneous electrogastrography (EGG) is a noninvasive test that detects gastric arrhythmias by recording the frequency and regularity of gastric myoelectrical activity. It has been used to investigate the mechanisms of gastric motility and sensation in patients with gastric motility disorders or motion sickness. By means of surface electrodes, EGG records gastric myoelectrical activity from the surface of the body. The cutaneous signals are low in amplitude, and thus must be markedly amplified. The resultant signals are heavily contaminated with noise, and visual analysis alone of EGG signals is inadequate. Consequently, EGG recordings require special methodology for acquisition, processing and analysis.
Colonic motility studies are used to assess the flow of intraluminal contents, the motions of the colonic wall that induce flow, and the control systems that integrate and regulate these processes. The approaches employed have consisted of manometric techniques to record colonic contractions, barostatic methods to measure colonic tone, and recordings of myoelectric signals from the colon that initiate and control muscular contractions. However, the study of colonic motility in a clinical setting proves to be difficult. Accurate positioning of the probes via colonoscopy requires pre-procedure cleansing of the colon, which raises the possibility of altered physiology. In contrast to other segments of the gastrointestinal tract, contents move through the colon in hours or days, instead of seconds to minutes; thus, prolonged observations are needed. Moreover, in contrast to the upper gastrointestinal tract, in which reliable manometric recordings can be obtained, the larger diameter of the colon hinders the accurate detection of manometric events. And finally, all of these techniques, which continue to be used extensively in a research context, have not yet been standardized for routine clinical use.
An American Gastroenterological Association guideline on nausea and vomiting (AGA, 2001) concluded that “the place of such tests of motor function as gastric emptying studies, electrogastrography, and manometry have not been defined, and the yield of such diagnostic studies has not been adequately compared with a therapeutic trial of an antiemetic and/or prokinetic agents.” An American Gastroenterological Association guideline on constipation (AGA, 2000) stated that colonic manometry “is not generally available and is not appropriate for most patients, except in research settings.” The consensus opinion of the American Motility Society Clinical GI Motility Testing Task Force on the performance and clinical utility of EGG (Parkman et al, 2003) stated that no therapies have convincingly demonstrated in controlled studies that correcting abnormalities detected by EGG improves upper gastrointestinal symptoms. Proposed clinical indications for performance of EGG in patients with unexplained nausea, vomiting and dyspeptic symptoms must be validated by prospective controlled investigations
New approach for evaluating gastric motility function in patients with functional dyspepsia and other upper functional gastrointestinal disorders is the use of an ambulatory diagnostic test pill, the SmartPill (SmartPill Corporation; Buffalo, NY). On July 20, 2006, the Unites States Food and Drug Administration cleared the SmartPill GI Monitoring System through the 510(k) process for use as an aid in evaluating patients with suspected motility disorders such as gastroparesis. This wireless, ingestible, medical device assesses pH and pressure in the gastrointestinal lumen. When the capsule reaches the duodenum, the change in pH (from acidic to alkaline) indicates this transition, allowing an assessment of gastric emptying.
As it passes through the gastrointestinal tract, miniaturized sensor technology measures pressure, temperature, and pH, as well as real and elapsed time. Acquired data are continuously transmitted over very low power radiofrequencies to a small receiver that can be worn on the patient`s belt. Although the capsule normally has a transit time ranging from 24 to 48 hours, it is capable of transmitting data continuously for more than 72 hours in patients with reduced motility. Once the device has passed, the data set is downloaded from the receiver to a laptop computer, and special software provides tools for data analysis and a graphical user interface that indicates when gastric emptying, small bowel/large bowel transit, and total gastrointestinal tract transit time of the capsule has occurred.
Prospective, randomized, controlled trials are needed to ascertain the clinical value of the SmartPill. Furthermore, since the SmartPill itself does not empty like a meal from the stomach, the technology is likely to only provide an estimate of upper gastrointestinal transit.