Simultaneous Assessment of Colonic Transit Using Wireless Capsule (SmartPill®) and Radiopaque Markers in Healthy Subjects and Effects of Gender

Abstract

Purpose: Colonic transit time (CTT) is used in the evaluation of constipation. Conventionally, CTT is assessed by ingesting radiopaque markers (Sitzmarks® (SZ) followed by abdominal x-ray(s). However, there is limited normative data, gender effects are unclear, and the technique is hampered by poor compliance and complex protocols. Recently, the SmartPill® (SP) wireless pH and pressure recording capsule has been advocated for assessing CTT. The aim of this multicenter study was to simultaneously assess and compare CTT as measured by SP with that of SZ in healthy subjects and to assess the effects of gender. Methods: After overnight fast, subjects ingested a nutrient bar (260 kcal) followed by a SZ capsule (24 markers) and a SP capsule. Subjects were instructed to wear a data receiver for 5 days or until SP was expelled and to record their bowel habit on a stool diary. Abdominal x-rays were obtained on day 2 and day 5. SP tracing was examined to assess gastric emptying time (GET) (time to sudden rise in pH >4), small bowel transit time (SBTT) (time to cecal entry with >1 pH drop after GET), CTT (time from cecal entry to abrupt temp. drop), and whole gut transit time (WGTT) (time from ingestion to abrupt temp. drop). The number of retained markers, transit times, and gender differences were assessed and compared. Results: Table (mean ± SEM, *=P< 0.05). 70 (36 M (mean age = 25 yrs)/34 F (mean age = 38 yrs), mean age = 37 yrs) were studied. The SP CTT correlated with% of markers expelled on day 2 (r = 0.72, P < 0.001) and on day 5 (r = 0.54, P < 0.001). The number of markers retained on Day 5 were greater (P < 0.001) in females and likewise, the SP CTT was also slower (P < 0.03) when compared to males. The GET (P < 0.002) and WGTT (P < 0.03) were also slower in females. All subjects expelled the SP. Conclusion: This large prospective study demonstrates very good correlation of colonic transit as measured by SmartPill® with conventional SZ technique. Also, women had slower gut transit time when compared to men. Thus, gender should be considered when interpreting CTT measurements. SP is a valid technique of measuring colonic and regional gut transit time.Table