In a patient with Zollinger-Ellison syndrome (ZES), why might they present with steatorrhea?

In Zollinger-Ellison syndrome (ZES), the excessive secretion of gastric acid is a characteristic feature due to gastrin-secreting tumors, usually located in the pancreas or duodenum. This hypersecretion of gastric acid can lead to increased acidity in the gastrointestinal tract, particularly in the small intestine, where pancreatic enzymes are active.

One crucial aspect of fat digestion is the role of pancreatic enzymes, such as lipase, which require an optimal pH to function effectively. The acidic environment created by the overproduction of stomach acid can inactivate these pancreatic enzymes. When lipase and other enzymes are inactivated, the body is unable to properly digest fats, which can result in steatorrhea, a condition marked by the presence of excess fat in the stool. As fats are not adequately emulsified and broken down, they are instead excreted in the feces, leading to the characteristic oily, foul-smelling stools associated with steatorrhea.

Thus, the increased stomach acid inactivating pancreatic enzymes is a direct mechanism by which patients with ZES can experience steatorrhea. Proper digestion of fats relies significantly on the integrity of these enzymes, making their inactivation a key factor in the development of this symptom.