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The objectives of the present study were to evaluate gastric and small bowel transit times of an indigestible solid matrix and to characterize the specific changes in intraluminal pH as a function of transit time through the gastrointestinal tract. Particular attention was paid to the lag time at the ileocecal junction. A Heidelberg capsule (HC), labeled with 10 microCi Indium-111, was given orally to six healthy male subjects 15 min after oral ingestion of 100 microCi of 99mTc-sulfur colloid as a liquid fatty meal (4 ml/kg). Intraluminal pH was monitored continuously via the HC. Gastric and small bowel transit of the radionuclides was monitored via external scintigraphy at 0.5-hr intervals. Gastric residence times (GRT) of the HC ranged from 2.8 to 4.8 hr. with a mean (+/- SD) of 3.6 +/- 0.8 hr. These values were independent of the individual's weight, height, or body surface area. Small bowel transit times of the HC ranged from 2.8 to greater than 5.5 hr. which were consistent with the reported values of 3 to 5 hr. The lag times of the HC at ileocecal junction ranged from 0.8 to greater than 2.5 hr. The presence of the lag times at the ileocecal junction in all subjects confirmed that it acts as a valve or sphincter. Mouth-to-cecum transit times of the HC occurred within 9.0 hr in 50% of the subjects. In general, following a sharp rise upon pyloric passage of HC the pH dropped slightly but then increased linearly throughout the small intestine.(ABSTRACT TRUNCATED AT 250 WORDS)

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During the past few years, the clinical and experimental applications of autologous blood cells labeled with gamma-emitting radionuclides, i.e., technetium-99m (Tc-99m) and indium-111 (In-111) have continued to grow rapidly. Investigations have centered around developing techniques that would label blood cells efficiently without alteration of cell viability and their pathophysiologic integrity. Experimental and clinical applications have been aimed at the studies of in vivo cell kinetics and detecting abnormal lesions by external imaging. These will be discussed in detail together with their advantages and disadvantages, and the future directions will be outlined.