Pancreatitis Associated With EUS-Guided Pancreatic Cyst Ablation or Fine Needle Aspiration: An Adverse Event With a Therapeutic Benefit

Introduction: EUS-guided ablation of mucinous pancreatic cysts is emerging as a minimally-invasive therapeutic option. With cyst resolution rates ranging between 33-87%, this treatment option has shown increasing efficacy and improved safety when alcohol-free ablation protocols are used. Alcohol based protocols have reported SAE rates of 3-10% for which acute pancreatitis (AP) is the most common AE. Interestingly, among patients who develop AP as a complication following EUS-guided ablation, cyst resolution rates of 100% have been reported. Herein, we describe two patient cases as examples of this phenomena, specifically where post-procedural AP following diagnostic EUS (without ablative therapy) resulted in resolution of pancreatic cysts. Case Description/Methods: Case 1: 53F presented with a palpable abdominal mass. Imaging demonstrated an 8x7 cm cyst (Figure 1a-b) in the head of the pancreas with internal septations and calcifications in the cyst wall,consistent with an MCN. She underwent EUS-FNA with removal of 15 mL fluid at another institution. Post-procedurally, she developed significant AP requiring hospitalization for 7 days. After recovery from AP, the patient was evaluated in consideration of EUS-guided chemoablation. MRI performed 5 weeks following episode of AP showed reduction in size of the cyst to 3 cm. EUS performed at 11 weeks demonstrated complete resolution of cyst and surveillance MRIs and tumor markers remain normal at 9 and 18 months (Figure 1c-d). Case 2: 63M presented with an incidentally noted enlarging pancreatic cyst (Figure 2a-b). EUS demonstrated a 4x3 cm cystic lesion. FNA revealed minimal atypia by cytology, CEA 12K, and amylase 122, consistent with an IPMN with two worrisome features. Post-procedurally, he developed mild AP requiring a 2-day hospitalization. 10 months following this event, the patient had an MRI for the purposes of procedural planning prior to EUS-guided chemoablation. This demonstrated resolution of the IPMN (Figure 2c-d). Discussion: These cases demonstrate a phenomenon in which the inflammatory milieu associated with AP results in eradication of pancreatic mucinous cysts. This adds to the finding that in prospective trials where the outcomes of patients who develop AP following EUS-guided ablation are reported, the cyst ablation rates are 100%. We postulate this to be secondary to activation of an immunologic response, and/or associated tumor ischemia. While it is an adverse event, post-procedural AP can have the silver lining of resulting in cyst eradication.Figure 1.: (a) and (b) T2 weighted MRI showing a 7.2 x 6.6 cm cystic lesion in the head of pancreas (yellow arrow) with internal septations, causing displacement of gallbladder (red arrow). (c) and (d) T2 weighted MRI at 18 months following EUS-FNA induced pancreatitis showing complete resolution of previously visualized MCN. Cystic duct marked by red arrow, and pancreatic duct marked by green arrow.Figure 2.: (a) and (b) T2 weighted MRI showing a cystic lesion measuring 3.9 cm in the mid-body of the pancreas (yellow arrow), along with multiple unilocular subcentimeter cysts in the pancreatic body and tail (green arrows). Bile duct marked by red arrow. (c) and (d) T2 weighted MRI following EUS-FNA induced pancreatitis showing complete resolution of previously visualized IPMN, along with shrinkage of smaller cysts in the body and tail (green arrows).