A child with cystic fibrosis (CF) who has had recent weight loss and several large foul-smelling stools should first have her:

In the context of a child with cystic fibrosis who is experiencing recent weight loss and large, foul-smelling stools, the most critical first step is to assess compliance with Pancreatic Enzyme Replacement Therapy (PERT).

Cystic fibrosis often leads to pancreatic insufficiency, where the pancreas does not produce sufficient enzymes needed for the digestion and absorption of nutrients, particularly fats. When a child is not receiving adequate doses of PERT, they may experience malabsorption, resulting in weight loss and the characteristic foul-smelling, greasy stools due to undigested food. By confirming whether the child is taking the prescribed enzyme therapy as directed, the healthcare provider can determine if inadequate enzyme replacement is the root cause of these symptoms.

Once compliance with PERT is established, further assessments regarding dietary fat intake, caloric intake, or hydration status can be conducted to address any remaining nutritional concerns or deficiencies. However, ensuring proper use of PERT is a fundamental step in managing the child's nutritional needs effectively.