S1620 A Symptomatic Posterior Mediastinal Space Pseudocyst Managed by Cystgastrostomy Through a Hiatal Hernia

Abstract

Introduction: Pseudocysts are seen after acute pancreatitis (AP) and consist of collections of pancreatic secretions surrounded by a fibrous wall. Mediastinal extension of pseudocysts is a rare complication of AP. Here we describe the unique case of a large pseudocyst that extended along a hiatal hernia sac resulting in chest pain and dysphagia, requiring cystgastrostomy in the posterior mediastinal space. Case Description/Methods: A 64-year-old female with a history of a large hiatal hernia (HH) presented to the emergency room (ER) with gradual onset retrosternal pain and associated dysphagia of 1 week duration. She had a recent hospitalization for AP two months earlier. In the ER, vital signs were within normal limits. Cardiac evaluation, complete blood count, and comprehensive metabolic panel were unremarkable. Abdominal computed tomography revealed a 7 x 6.2 cm peripancreatic fluid collection extending through the diaphragm in the posterior mediastinal space, resulting in mass effect on the distal esophagus and HH sac (Figure 1A-C). Upper endoscopy revealed extrinsic-appearing narrowing in the distal esophagus immediately proximal to a 5 cm Hill grade IV HH. Endosonography (EUS) guided cystgastrostomy was successfully performed using a 10 mm x 10 mm electrocautery enhanced lumen apposing metal stent (LAMS). Post-procedure the patient reported symptomatic relief and was admitted for overnight observation. Repeat cross sectional imaging revealed significant reduction in the size of the pseudocyst (Figure 1D). EUS two weeks later revealed complete pseudocyst resolution and the LAMS was removed. Discussion: Mediastinal extension of a pseudocyst is a rare complication of acute pancreatitis. In prior reports, mediastinal pseudocysts have been managed by endoscopic aspiration, placement of plastic stents, or surgical drainage. To our knowledge, this is the first case of a cystgastrostomy performed through a hiatal hernia to drain a pseudocyst in the posterior mediastinum.Figure 1.: Axial (A) and coronal (B and C) views of the CT scan revealed a large pseudocyst extending into the posterior mediastinal space. The sagittal view (D) showed the lumen-apposing metal stent draining the pseudocyst into the hiatal hernia sac.