Tardive Peritonitis After Endoscopic Ultrasound-Guided Pancreatic Pseudocyst Drainage: A Case Report.

Here, we report a case of tardive peritonitis after endoscopic ultrasound (EUS)-guided transmural pancreatic pseudocyst drainage. A 50-year-old man was diagnosed with acute pancreatitis and a pancreatic pseudocyst measuring 5 cm. Ten months later, his pancreatic pseudocyst was 10 cm. We performed EUS-guided transmural drainage using a lumen-apposing metal stent. After two months, the stent was replaced with a double-pigtail plastic stent. Two months later, the patient developed fever and abdominal pain, and computed tomography revealed abdominal free air. He was diagnosed with peritonitis due to free air caused by a fistula rupture. The double-pigtail plastic stent was removed, and clipping was performed at the fistula site to achieve closure. The patient's symptoms subsequently improved. Long-term placement of a plastic stent for pancreatic pseudocysts makes recurrence less likely, but late adverse events due to stent placement can occur. Notably, fistula rupture can occur even when the fistula is well-formed several months after the initial drainage.