Accurate localization of a fall in pH within the ileocecal region: validation using a dual-scintigraphic technique.

Stereotypical changes in pH occur along the gastrointestinal (GI) tract. Classically, there is an abrupt increase in pH on exit from the stomach, followed later by a sharp fall in pH, attributed to passage through the ileocecal region. However, the precise location of this latter pH change has never been conclusively substantiated. We aimed to determine the site of fall in pH using a dual-scintigraphic technique. On day 1, 13 healthy subjects underwent nasal intubation with a 3-m-long catheter, which was allowed to progress to the distal ileum. On day 2, subjects ingested a pH-sensitive wireless motility capsule labeled with 4 MBq (51)Chromium [EDTA]. The course of this, as it travelled through the GI tract, was assessed with a single-headed γ-camera using static and dynamic scans. Capsule progression was plotted relative to a background of 4 MBq ¹¹¹Indium [diethylenetriamine penta-acetic acid] administered through the catheter. Intraluminal pH, as recorded by the capsule, was monitored continuously, and position of the capsule relative to pH was established. A sharp fall in pH was recorded in all subjects; position of the capsule relative to this was accurately determined anatomically in 9/13 subjects. In these nine subjects, a pH drop of 1.5 ± 0.2 U, from 7.6 ± 0.05 to 6.1 ± 0.1 occurred a median of 7.5 min (1-16) after passage through the ileocecal valve; location was either in the cecum (n = 5), ascending colon (n = 2), or coincident with a move from the cecum to ascending colon (n = 2). This study provides conclusive evidence that the fall in pH seen within the ileocolonic region actually occurs in the proximal colon. This phenomenon can be used as a biomarker of transition between the small and large bowel and validates assessment of regional GI motility using capsule technology that incorporates pH measurement.

Do stool form and frequency correlate with whole-gut and colonic transit? Results from a multicenter study in constipated individuals and healthy controls.

OBJECTIVES: Despite a lack of supportive data, stool form and stool frequency are often used as clinical surrogates for gut transit in constipated patients. The aim of this study was to assess the correlation between stool characteristics (form and frequency) and gut transit in constipated and healthy adults. METHODS: A post hoc analysis was performed on 110 subjects (46 chronic constipation) from nine US sites recording stool form (Bristol Stool Scale) and frequency during simultaneous assessment of whole-gut and colonic transit by wireless motility capsule (WMC) and radio-opaque marker (ROM) tests. Stool form and frequency were correlated with transit times using Spearman's rank correlation. Accuracy of stool form in predicting delayed transit was assessed by receiver operating characteristic analysis. RESULTS: In the constipated adults (42 females, 4 males), moderate correlations were found between stool form and whole-gut transit measured by WMC (r=-0.61, P<0.0001) or ROM (-0.45, P=0.0016), as well as colonic transit measured by WMC (-0.62, P<0.0001). A Bristol stool form value <3 predicted delayed whole-gut transit with a sensitivity of 85% and specificity of 82% and delayed colonic transit with a sensitivity of 82% and specificity of 83%. No correlation between stool form and measured transit was found in healthy adults, regardless of gender. No correlation was found between stool frequency and measured transit in constipated or healthy adults. The correlation between stool frequency and measured transit remained poor in constipated adults with <3 bowel movements per week. CONCLUSIONS: Stool form predicts delayed vs. normal transit in adults. However, only a moderate correlation exists between stool form and measured whole-gut or colonic transit time in constipated adults. In contrast, stool frequency is a poor surrogate for transit, even in those with reduced stool frequency.

Investigation of colonic and whole-gut transit with wireless motility capsule and radiopaque markers in constipation.

BACKGROUND & AIMS: Colonic transit time (CTT) traditionally is assessed with radiopaque markers (ROMs), which requires radiation and is hindered by lack of standardization and compliance. We assessed regional and CTT with the SmartPill (SmartPill Corporation, Buffalo, NY), a new wireless pH and pressure recording capsule, in constipated and healthy subjects and compared this with ROM. METHODS: Seventy-eight constipated (Rome II) and 87 healthy subjects ingested a 260-kcal meal, a ROM capsule, and the SmartPill. Subjects wore a data receiver and kept daily stool diaries for 5 days. SmartPill recordings assessed CTT, whole-gut transit time (WGTT), small-bowel transit time, and gastric emptying time. Abdominal radiographs on days 2 and 5 assessed ROM transit. Sensitivity/specificity and receiver operating characteristics (ROCs) of each technique and utility were compared. RESULTS: Gastric emptying time, CTT, and WGTT were slower (P < .01) in constipated subjects than controls. CTT was slower in women than men (P = .02). Day 2 and day 5 ROM transits were slower (P < .001) in constipated subjects. Correlation of the SmartPill CTT with ROMs expelled on day 2/day 5 was r = 0.74/r = 0.69 in constipation, and r = 0.70/r = 0.40 in controls, respectively. The diagnostic accuracy of the SmartPill CTT to predict constipation from ROC was 0.73, with a specificity of 0.95. These were comparable with those of day 5 ROM (ROC, 0.71; specificity, 0.95). CONCLUSIONS: The SmartPill is a novel ambulatory technique of assessing regional (gastric, small bowel, colonic) and WGTT without radiation. It reveals hitherto unrecognized gender differences and upper-gut dysfunction in constipation. It correlates well with ROM and offers a standardized method of discriminating normal from slow colonic transit.