Recent developments in gastrointestinal motility

Ingestible Sensors and Sensing Systems for Minimally Invasive Diagnosis and Monitoring: The Next Frontier in Minimally Invasive Screening

Ingestible electronic systems that are capable of embedded sensing, particularly within the gastrointestinal (GI) tract and its accessory organs, have the potential to screen for diseases that are difficult if not impossible to detect at an early stage using other means. Furthermore, these devices have the potential to (1) reduce labor and facility costs for a variety of procedures, (2) promote research for discovering new biomarker targets for associated pathologies, (3) promote the development of autonomous or semiautonomous diagnostic aids for consumers, and (4) provide a foundation for epithelially targeted therapeutic interventions. These technological advances have the potential to make disease surveillance and treatment far more effective for a variety of conditions, allowing patients to lead longer and more productive lives. This review will examine the conventional techniques, as well as ingestible sensors and sensing systems that are currently under development for use in disease screening and diagnosis for GI disorders. Design considerations, fabrication, and applications will be discussed.

The effect of luminal content and rate of occlusion on the interpretation of colonic manometry

BACKGROUND

Manometry is commonly used for diagnosis of esophageal and anorectal motility disorders. In the colon, manometry is a useful tool, but clinical application remains uncertain. This uncertainty is partly based on the belief that manometry cannot reliably detect non-occluding colonic contractions and, therefore, cannot identify reliable markers of dysmotility. This study tests the ability of manometry to record pressure signals in response to non-lumen-occluding changes in diameter, at different rates of wall movement and with content of different viscosities.

METHODS

A numerical model was built to investigate pressure changes caused by localized, non-lumen-occluding reductions in diameter, similar to those caused by contraction of the gut wall. A mechanical model, consisting of a sealed pressure vessel which could produce localized reductions in luminal diameter, was used to validate the model using luminal segments formed from; (i) natural latex; and (ii) sections of rabbit proximal colon. Fluids with viscosities ranging from 1 to 6800 mPa s(-1) and luminal contraction rates over the range 5-20 mmHg s(-1) were studied.

KEY RESULTS

Manometry recorded non-occluding reductions in diameter, provided that they occurred with sufficiently viscous content. The measured signal was linearly dependent on the rate of reduction in luminal diameter and also increased with increasing viscosity of content (R(2) = 0.62 and 0.96 for 880 and 1760 mPa s(-1), respectively).

CONCLUSIONS & INFERENCES

Manometry reliably registers non-occluding contractions in the presence of viscous content, and is therefore a viable tool for measuring colonic motility. Interpretation of colonic manometric data, and definitions based on manometric results, must consider the viscosity of luminal content.

Twenty-four hour spatiotemporal mapping of colonic propagating sequences provides pathophysiological insight into constipation

Colonic propagating sequences (PS)s are a major determinant of luminal propulsion. A global appreciation of spatiotemporal patterning of PSs requires evaluation of 24 h pan-colonic recordings, a difficult task given that PSs are relatively infrequent events that are not uniformly distributed throughout the colon. Here we developed a means of space-time-pressure 'mapping' in a condensed format, 24 h of colonic recording in such a manner that readily permits an overall view of colonic antegrade and retrograde colonic PSs within a single figure. Such graphical representation readily permits appreciation and identification of aberrant patterns in severe constipation and may be an important clinical and research tool in the assessment of colonic motor disorders.