Background Infection is still one of the common adverse events after endoscopic drainage of peripancreatic effusion. Acid-suppressive drugs can inhibit pancreatic exocrine and are widely used in patients with pancreatitis. Acid-suppressing drugs affect intestinal microbes by inhibiting the secretion of stomach acid. However, it is not clear whether acid-suppressive drugs affect the microorganisms in the peripancreatic effusion and affect the postoperative complications.

Methods This study was a randomized, placebo-controlled, double-blind clinical trial. This trial enrolled 45 patients at our medical center. All patients were divided into an acid-inhibited group and a non-acid-inhibited group. In the acid-suppressive group, patients received acid-suppressive medication (omeprazole 80mg intravenously) 7 days before endoscopic drainage. In the non-acid inhibition group, patients received a placebo (intravenous saline administration) starting 7 days before the endoscopic transmural drainage procedure. The main outcome of our study was to observe the difference in microbiota in the two groups of cyst fluid.

Results A total of 25 patients were included in the acid-inhibited group and 20 patients were included in the non-acid-inhibited group. The two groups were well-matched in terms of demographic characteristics, etiology of pancreatitis, cyst types, and cyst locations. Both groups achieved similar rates of clinical success and technical success (p>0.05). There were no significant differences between the two groups in terms of postoperative infection, bleeding, and recurrence rates (p>0.05). In terms of postoperative C-reactive protein levels, the acid-suppressing group was significantly higher than the non-acid-suppressing group (p<0.05). We conducted 16S microbial sequencing analysis to investigate the microbial composition in the cyst fluid, and we found no significant difference in α diversity between the antibiotic group and the non-antibiotic group. However, there was a significant difference in β diversity analysis between the two groups.

Conclusions Acid-suppressing drugs can change the microbial composition of pancreatic effusion, which may potentially affect the infection after endoscopic drainage.