Relationship Between the Colonic Transit of Wireless Capsule (Smartpill®) and Radio Opaque Markers in Constipation

Abstract

Purpose: Recently, it has been shown that the colonic and whole gut transit time as assessed by a novel wireless pH and pressure recording capsule (SmartPill® (SP)) correlates well with radio opaque markers (ROM), both in constipated and healthy subjects (Am J Gastroenterol 2007;1075:S512). Whether the SP traverses the colon at the same speed as ROM is however not known. This multicenter study aimed to simultaneously assess and compare the location of SP capsule with the majority of ROM that were either present on a plain x-ray of the abdomen taken at two specified time intervals or with those that had been expelled in constipated (Rome II) and healthy subjects. Methods: After overnight fast, subjects ingested a nutrient bar (260 kcal) followed by a Sitzmark® capsule (24 ROMs) and a SP capsule. Subjects wore a data receiver for 5 days or until SP was expelled and kept stool diary. Abdominal x-rays were obtained on days 2 & 5. The x-rays obtained on day 2 and day 5 were analyzed by two independent observers and the number of ROM located in the right colon and the left colon were counted. The difference between the number of markers ingested and those retained on the x-rays were taken as markers expelled. The location of the SP on day 2 or day 5 x-ray with respect to the right and left colon was also recorded. Chi-square test was used to examine the association between the location of the majority of ROM on the day 2 and day 5 x-ray with the location of the SP. Results: 73 constipated (m/f = 8/65; mean age = 46 ± 1.7 years) and 91 healthy (m/f = 48/43; mean age = 37 ± 1.3 years) subjects participated. Table shows the number of subjects in whom the SP and the majority of ROM were seen on day 2 and day 5 x-rays and in the two colonic segments as well as those that had been expelled. The location of SP in the colon and when expelled on day 2 and day 5 were strongly associated with the location of the majority of ROM (P < 0.0001). Likewise, the location of SP was also associated with the majority of ROM in the constipated and healthy group of subjects.TableConclusion: The location of SP is strongly associated with the region of the colon where a majority of retained markers were seen or with those that had been expelled. This suggests that SP traverses the colon at approximately the same speed as ROM. These data further reaffirm that SP is a useful and valid technique of assessment of colonic and whole gut transit time.