Which condition is NOT an indication for using parenteral nutrition in chemotherapy patients?

Parenteral nutrition is typically utilized in patients who cannot meet their nutritional needs via the enteral route, particularly in the context of chemotherapy, where various gastrointestinal complications can arise. Among the listed conditions, constipation is not usually a reason to initiate parenteral nutrition.

Nausea and vomiting, diarrhea, and ileus are conditions that can severely compromise a patient's ability to absorb nutrients or may lead to inadequate caloric intake. Nausea and vomiting can prevent patients from consuming food orally, while diarrhea can lead to nutrient malabsorption and loss. Ileus, characterized by a temporary paralysis of the bowel, can also hinder normal digestive function and absorption.

In contrast, constipation, while it can cause discomfort and may require management to prevent complications, does not typically impede the ability to consume oral nutrition. Patients with constipation can often eat and absorb nutrients, and their situation is usually managed with dietary adjustments, medications, and other supportive measures rather than resorting to parenteral nutrition. Therefore, it stands out as the condition that is not an indication for the use of parenteral nutrition in chemotherapy patients.