Exploring pyloric dynamics in stenting – Using a distensibility technique

Perforated duodenal ulcers can be treated with a stent. Stent migration is a severe complication, sometimes requiring surgery. Pyloric physiology during stent-treatment has not been studied and mechanisms for migration are unknown. To investigate the pyloric response to distention, mimicking stent-treatment, using the EndoFLIP, a non-survival study in five pigs was carried out, followed by a pilot study in one volunteer. Animals were gastroscoped during anaesthesia and the EndoFLIP was placed straddling the pylorus. Baseline distensibility readings were performed at stepwise balloon distentions to 20 ml, 30 ml, 40 ml and 50 ml, measuring pyloric Cross Sectional Area and pressure. Measurements were repeated after administration of a pro-kinetic drug and after a liquid meal. In the human study readings were performed in conscious sedation at baseline and after stimulation with metoclopramide. During baseline readings the pylorus was shown to open more with increasing distention together with higher amplitude motility waves. Reaching maximum distention-volume (50 ml), pyloric pressure increased significantly (p = 0.016) and motility waves disappeared. After pro-kinetic stimulation the pressure decreased and the motility waves increased in frequency and amplitude. After food stimulation the pressure stayed low and the motility showed increase in amplitude. During both tests the pylorus showed higher pressure and lack of motility waves at maximum probe distention. The pylorus seems to acts as a sphincter at low distention but when further dilated starts acting as a pump. Fully distended the pyloric motility disappears and the pressure remains high, suggesting that a stent with high radial force might show less migration.