What is enteral and parenteral nutrition?

If, despite your best efforts, you can't eat enough to stay strong, your team may suggest nutrition support. There are two main forms:

• Enteral nutrition gives nutrients in liquid form through a feeding tube into the stomach or small intestine.
• Parenteral nutrition gives nutrients directly into a vein through a catheter, used when the stomach and intestines can't be used.

The words come from Greek. Enteral means "through the intestine." Parenteral means "beside the intestine," in other words, going around it. That difference is the whole decision.

The rule that decides which one

Doctors pick based on one thing first: whether your gut still works. The National Cancer Institute puts it plainly, saying the best method depends on how well the gastrointestinal tract is functioning, and that enteral nutrition is recommended when the tract still works.

There is a good reason for that preference. Food moving through the bowel keeps the gut lining fed and active. Skip the gut entirely and you lose that, and you add a catheter sitting in a large vein, which brings its own risks.

So the short version is: use the gut if the gut is usable. Parenteral nutrition is for when it is not, such as a blocked bowel, a bowel that cannot absorb, or severe ongoing vomiting.

What the tubes actually are

For enteral feeding, NCI describes three routes.

A nasogastric tube goes in through the nose, down the throat, and into the stomach or small intestine. No surgery is needed. It is used when support is expected for only a few weeks.

A gastrostomy tube goes directly into the stomach through the wall of the abdomen. This is the choice for long-term feeding, or when a tube through the nose and throat is not workable. People often call it a G-tube or PEG tube.

A jejunostomy tube goes into the small intestine through an opening in the abdomen, bypassing the stomach.

For parenteral nutrition, the fluid runs through a catheter placed under the skin into a large vein in the upper chest, or in some cases into a vein in the arm.

When this comes up in cancer care

Nutrition support is usually raised when eating has been blocked or made painful for a stretch, not after one bad week. Common situations include a tumor blocking the throat or esophagus, severe mouth and throat sores from radiation to the head and neck, and a bowel obstruction.

NCI's guidance for stem cell transplant patients gives a useful yardstick. Support is considered when someone is malnourished and expected to be unable to eat or absorb enough for a prolonged period, described as more than 7 to 14 days.

What to ask before agreeing

Before this step, your team may screen you for malnutrition, and a registered dietitian can do a full assessment and build a nutrition care plan.

Useful questions: How long do you expect I will need this? Can I still eat or drink by mouth alongside it? Who manages the tube or line at home, and what training do I get? What are the signs of a problem that should trigger a call?

Nutrition support is often temporary. Ask what has to improve for it to come out, so you have a target rather than an open-ended arrangement.