3.1　Introduction

Pancreatic exocrine insufficiency is defined as partial or complete loss of digestive enzyme and bicarbonate secretion.While several pathomechanisms may impair intraluminal availability of pancreatic secretions，progressive destruction of functioning pancreatic tissue in chronic pancreatitis remains its most frequent cause.The pancreas has a large functional reserve，therefore，typical symptoms of pancreatic exocrine insufficiency such as steatorrhoea，weight loss and abdominal complaints caused by maldigestion usually become apparent in advanced stages，only.However，also patients with mild to moderate pancreatic exocrine insufficiency have an increased risk of nutritional deficiencies.This is one of the reasons why experts agree that pancreatic exocrine insufficiency should be searched for actively in patients with chronic pancreatitis and usually requires treatment（HaPanEU 2016）.However，both，diagnosis and treatment of pancreatic exocrine insufficiency are demanding:available tests have either limited availability due to invasiveness and/or high costs or have limited sensitivity and specificity.Furthermore，galenic preparation of pancreatic enzyme supplements that ensures availability of enzymes in the small intestinal lumen together with meal components is challenging.This chapter focuses on pathophysiology and diagnosis of pancreatic exocrine insufficiency in chronic pancreatitis.(https://www.daowen.com)