Imaging of endoscopic cystogastrostomy in pancreatic walled-off necrosis: what the radiologist needs to know Anthony Abou Karam , 1 Arya Bagherpour, 2 Jesus Calleros, 1 Shaked Laks 1 1 Texas Tech University Medical Center El Paso, El Paso, TX, USA 2 University of Texas Medical Branch in Galveston, UTMB, Galveston, TX, USA Abstract Acute pancreatitis is a frequent entity encountered by radiologists. In 2012, the Atlanta criteria were revised to help radiologists use a common nomenclature when describing acute pancreatitis and its complications. One delayed complication of acute necrotizing pancreatitis in walled-off necrosis, a collection seen at least 4 weeks after an episode of acute pancreatic necrosis and/or acute peripancreatic necrosis. Multiple treatments have been adapted in the setting of walled-off necrosis, including endoscopic cystogastrostomy. The focus of this article is to familiarize the radiologist with the imaging appear- ance of this procedure as well as, review the outcomes and potential complications of endoscopic cystogastros- tomy. Key words: Walled-off necrosis—Cystogastrostomy— Pancreas Acute pancreatitis is frequently encountered in everyday practice with a yearly incidence of 13–45 in 100,000 [1]. The leading causes of acute pancreatitis include gall- stones and alcohol use [2]. The 2012 revised Atlanta criteria divide acute pancreatitis in two types: Interstitial edematous pancreatitis (EIP) and necrotizing pancreati- tis (NP). [3, 4]. The classification also emphasized nomenclature for the collections that can occur in the setting of interstitial edematous and necrotizing pancre- atitis. In the acute phase, patient may present with acute peripancreatic fluid collection in the setting of EIP or an acute necrotic collection in the setting of NP. If the collection persists longer than 4 weeks after the initial episode, they are referred to as a pseudocyst in the case of EIP and walled-off necrosis in the setting of NP. The management of walled-off necrosis depends on multiple factors, including collection characteristics and local complications. Endoscopic cystogastrostomy with necrosectomy is a minimally invasive procedure which can be used to manage walled-off necrosis. Radiologists should be familiar with the radiologic appearance of this procedure as well as its outcomes and possible compli- cations. Imaging features of acute necrotic collection and walled-off necrosis Acute necrotic collection is seen in the setting of peri- pancreatic and or pancreatic necrosis within less than 4 weeks of the initial pancreatitis episode. It usually consists of heterogeneous, non-enhancing peripancreatic fluid and soft tissue with or without pancreatic necrosis (Fig. 1A, B). The absence of pancreatic involvement can render the diagnosis of acute necrotic collection chal- lenging. If the acute necrotic collection matures and forms a non-epithelized wall then it becomes walled-off necrosis (Fig. 2A, B). Walled-off necrosis can involve the pan- creas and/or peripancreatic tissues. The peripheral rim of walled-off necrosis can mildly enhance. The internal contents may be heterogeneous but should not enhance. When infected, walled-off necrosis can also contain air (Fig. 3)[5]. Walled-off necrosis treatment with focus on endoscopic cystogastrostomy In cases of walled-off necrosis, medical management is the first step. Patients are usually observed and offered supportive treatment. Invasive procedures such as Correspondence to: Anthony Abou Karam; email: anthony.karam@ ttuhsc.edu ª Springer Science+Business Media, LLC, part of Springer Nature 2018 Abdominal Radiology Abdom Radiol (2018) https://doi.org/10.1007/s00261-018-1584-2