Transuterine Puncture of the Fetal Stomach Provides Access to the Small Bowel in the Rabbit

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Abstract
The prevention of perinatal complications of congenital gastrointestinal (GI) diseases such as cystic fibrosis may require prenatal treatment. New Zealand White rabbits were evaluated as a potential animal model to study gastrointestinal anatomy and transit in the fetus. The lengths of the GI tract of fetuses at 21/31 and 28/31 days gestation were established, and gastric volume was measured. Gastric volume at 28 days gestation averaged 2.6 mL, adequate to permit instillation of a solution into the fetal stomach. A study was then carried out to establish gastric emptying and delivery of the solution into the small bowel. Using ultrasound guidance, the stomachs of 26 fetuses from 7 litters were punctured and 0.5 mL of dilute barium was injected. A cesarean section was performed 4 h later and the progression of barium though the GI tract was measured. In 18/26 (69.2%) of the fetuses barium was successfully delivered to the lumen of the stomach. In these 18 fetuses, barium progressed to the duodenum in 15 (58%), the jejunum in 13 (50%), and the ileum in 8 (31%). The stomach of the 3.5- to 4-week-old fetus is large enough to allow transuterine delivery of a solution of dilute barium. Gastric and intestinal motility in the 25-day-old rabbit fetus is coordinated and results in delivery of barium to the small bowel in 50% of animals successfully injected. The results suggest that the rabbit is an acceptable model for the study of gastrointestinal delivery of therapeutic drugs or genes to the fetus.