Impaired breakdown of food in the digestive tract so that nutrients are poorly digested and absorbed. Common causes include insufficient pancreatic enzymes, as in chronic pancreatitis or cystic fibrosis, lack of stomach acid, and bile salt deficiency after gallbladder or ileal disease. Undigested fat produces greasy, foul-smelling stools, while undigested carbohydrate ferments in the colon causing gas and bloating. Diagnosis uses stool tests, breath tests, and imaging of the pancreas. Treatment replaces what is missing: pancreatic enzyme capsules taken with meals transform outcomes for many patients, alongside dietary adjustments and correction of resulting nutrient deficiencies.