Irreversible electroporation (IRE) therapy utilizes high voltage small microsecond pulse lengths to create nanopores in cell membrane and induce apoptosis. In recent years, it has been utilized as a treatment for patients with pancreatic cancer. It can be administered either intraoperatively, laproscopically, or percutaneously. Prior reported complications included gastrointestinal bleeding (typically ulcers in the duodenum), bile/pancreatic leak, portal vein thrombosis, perforation, pancreatitis and arrhythmias. Reported here is a case of a massive delayed GI bleed from a splenic artery pseudoaneurysm with fistula to the distal duodenum post IRE treatment. Case Presentation 56 year old female with unresectable pancreatic adenocarcinoma who had received chemotherapy, radiation, plastic stent placement, and intraoperative IRE four months prior to development of hematemesis followed by hematochezia. Upon presentation, the patient was tachycardic with maroon colored stool on rectal exam. Her hemoglobin had dropped from 12.6 to 8.7. EGD done at that time revealed no lesions or blood. CT imaging showed a 4cm x 3cm collection containing gas and liquid in the IRE treatment bed concerning for possible abscess. The patient improved with antibiotics, had no further bleeding, and was discharged home. One month later, she had recurrent hematemesis followed by hematochezia. She presented in hemorrhagic shock and required an emergent EGD which again failed to reveal any blood or lesions. Shortly after this EGD, she had a third bleeding event that prompted a CT angiography. A pseudoaneurysm of the splenic artery was found to be abutting the bowel distal to the ligament of Treitz with intraluminal blush consistent with active bleed. The patient was taken for emergent embolization. She had no recurrent bleeding in the following 3 months of follow up. Delayed massive gastrointestinal hemorrhage as the result of a splenic artery pseudoaneurysm to small bowel fistula following IRE treatment had not previously been reported in the literature. The proposed pathophysiology of this complication includes direct treatment effect on the splenic artery in addition to post treatment inflammation/fluid collection creating an environment for contact and fistula formation between the artery and the small bowel. Clinical awareness of this possible complication could support the use of CT angiography prior to endoscopic evaluation in the appropriate patient population.Figure: Splenic artery aneurysm (arrow) with associated inflammation in the area of the proximal jejunum.Figure: Sagittal view of splenic artery pseudoaneurysm (arrow).