A technical review and clinical assessment of the wireless motility capsule

Abstract

The wireless motility/pH capsule (WMC) is an orally ingested, nondigestible, data recording device that enables the simultaneous assessment of regional and whole gut transit. Approved by the US Food and Drug Administration for the evaluation of patients with suspected delayed gastric emptying and the evaluation of colonic transit time in patients with chronic idiopathic constipation, this capsule continuously measures the temperature, pH, and pressure of its surrounding environment while traveling through the gastrointestinal tract (via gut peristalsis) until exiting the body through the anus. Validated patterns in pH and temperature recordings allow for accurate measurement of gastric emptying, small bowel transit, colonic transit, and whole gut transit times. The WMC is a nonradioactive, office-based, gastrointestinal transit testing modality shown in several clinical trials to be a suitable alternative to scintigraphy and radiopaque marker studies in measuring gastric emptying, small bowel, colonic, and whole gut transit times. Unlike widely available transit tests, which provide only region-specific transit data, the WMC offers the benefit of measuring gastric, small bowel, and colonic transit times in a single examination. The WMC also provides intraluminal pressure readings throughout the digestive tract, offering a noninvasive means by which to assess gastrointestinal motility. The WMC should be considered the transit study of choice for individuals suspected of having altered transit in more than one region of the gastrointestinal tract. This review summarizes the features and performance characteristics of the WMC as well as provides a summary on how this diagnostic modality is most effectively used in the assessment of gastrointestinal symptom complexes due to suspected abnormalities in transit.

Keywords: Wireless motility capsule; constipation; gastrointestinal motility; gastrointestinal transit testing; gastroparesis.

Figure 1

The wireless motility capsule.

Figure 2

A sample motility graph showing data from a wireless motility capsule. Temperature, pH, and pressure measurements can be used to calculate gastric emptying, small bowel transit, colonic transit, and whole gut transit times, as well as other motility information.

Figure 3

A portion of the wireless motility capsule tracing spanning the time of ingestion to the time of capsule passage into the cecum in a gastroparesis patient with associated intestinal pseudo-obstruction. The sustained drop in pH (shaded box) at 23 hours and 15 minutes indicates the capsule's exit from the small bowel and its entrance into the cecum. The drop and subsequent rise in pH characteristically seen with passage of the capsule through the stomach is not found in this tracing, as the patient had previously undergone a gastrectomy.

Figure 4

A tracing of a wireless motility capsule in a patient with refractory idiopathic chronic constipation. The capsule entered the cecum at 9 hours (shown by a sustained drop in pH; shaded box on the left side) and exited the body at 125 hours (shown by a drop in temperature; shaded box on the right side), yielding a colonic transit time of 116 hours.

Figure 5

A tracing of a wireless motility capsule in a patient with overlapping upper and lower gastrointestinal symptom complex. The capsule exited the stomach at 3 hours and 16 minutes (shown by an abrupt rise in pH; first shaded box), demonstrating a normal gastric emptying time. The capsule exited the small bowel at 7 hours and 32 minutes (shown by a sustained drop in pH; second shaded box), yielding a normal small bowel transit time of 4 hours and 16 minutes. The capsule exited the body at 46 hours and 52 minutes (shown by an abrupt drop in temperature; third shaded box), yielding a normal colonic transit time of 39 hours and 20 minutes.