The patient most likely has a pancreatic pseudocyst, which is a complication of pancreatitis. Pancreatic pseudocyst is not a true cyst; it is lined by granulation tissue and collagen. It contains pancreatic juices and lysed blood, so rupture would spill the active digestive enzymes onto the adjacent viscera, paicularly the stomach, small intestine, and transverse colon. Digestive action produces potentially severe gastrointestinal hemorrhage. Anaphylactic shock results from massive activation of the IgE-mediated branch of the immune system. Pancreatic secretions do not elicit an IgE response. The classic abdominal cyst that ruptures, producing anaphylactic shock, is a hydatid cyst. Carcinomatosis is widespread serosal spread of a carcinoma, typically due to tumor spillage into a body cavity. Although this may occur with pancreatic mucinous cystadenocarcinoma, this disease is far less likely to occur than is pancreatic pseudocyst in a patient with chronic pancreatitis. Pancreatic pseudocyst is not an infective disease. Although septic abscesses do occur in the abdomen, and may even complicate a pancreatic pseudocyst, the danger of rupture is more associated with tissue destruction by pancreatic enzymes than with infection. Ref: Fisher W.E., Anderson D.K., Bell R.H., Saluja A.K., Brunicardi F.C. (2010). Chapter 33. Pancreas. In F.C. Brunicardi, D.K. Andersen, T.R. Billiar, D.L. Dunn, J.G. Hunter, J.B. Matthews, R.E. Pollock (Eds), Schwaz's Principles of Surgery, 9e.