The use of dual-isotope imaging to compare the gastrointestinal transit of food and pancreatic enzyme pellets in cystic fibrosis patients

Cystic fibrosis patients require pancreatic enzyme supplements to aid food digestion. It is suspected that incorrect delivery of this enzyme may result in both significant malabsorption and the development of strictures in the proximal colon caused by the high-dose supplement reaching this region before the food. Investigations into the drug's delivery were performed using dual-isotope imaging; a method was developed to directly label the enteric-coated enzyme pellets with In-111, re-applying the enteric coating afterwards, and this was then ingested with a pancake meal labelled with Tc-99(m)-tin colloid. Consecutive image data, acquired over a period of greater than or equal to 4 h using a dual-headed gamma camera, were analysed to assess intestinal transit. In-vitro stability checks on these labelling techniques were encouraging, showing < 2% Tc-99(m) and < 7% In-111 elution over 90 min in hydrochloric acid. In 5 of the 12 patients studied to date, the pellets were seen to pass through significantly faster than the food, with a mean difference in 50% gastric emptying time of greater than 93 min. The mean absolute difference in emptying time for all 12 patients was > 67 min. Thus, a technique has been developed to effectively radiolabel pancreatic enzyme pellets, and analysis of dual-isotope images using this preparation, together with radiolabelled solid food, has demonstrated significant differences in the transit of these two substances through the gastrointestinal tract of some cystic fibrosis patients. ((C) 1998 Lippincott Williams & Wilkins).