This guide for clinicians focuses on pancreatic exocrine insufficiency (PEI) in patients living with pancreatic cancer. PEI is when the pancreas does not produce enough digestive enzymes, or when the amounts of enzymes secreted into the duodenum are insufficient. PEI results in maldigestion, and sometimes malabsorption and malnutrition. PEI can result when pancreatic function is affected due to disease or surgery – for example, from pancreatic cancer and associated surgeries, stomach cancer, diabetes and irritable bowel syndrome.