13.1 Gastrointestinal Effects

CPHON Test Content Outline (TCO) IV.A.4 tests gastrointestinal acute, chronic, and late effects of chemotherapy, radiation, hematopoietic stem cell transplantation (HSCT), and supportive medicines. It is not the emergency chapter. Full algorithms for typhlitis (neutropenic colitis), pancreatitis, and mechanical bowel obstruction live in Domain V. Here the nurse names the exposure, grades the mucosa and the gut, keeps calories moving, and chooses the right antiemetic clock.

A 5-year-old on high-dose methotrexate who will not drink, a 14-year-old who vomits in the parking garage before the bag is hung, and a toddler on irinotecan with early watery stools and a flushed face are all gastrointestinal-effect patients. Compare them with yesterday's intake, not with "kids do not like hospital food."

Mucositis: oral and gastrointestinal

Mucositis is injury to rapidly dividing epithelium from the mouth through the gut. High-dose methotrexate, high-dose cytarabine, anthracyclines, melphalan (especially autologous HSCT), radiation to the head, neck, or abdomen, and myeloablative conditioning are classic triggers. Pain, drooling, refusal to swallow, and white or ulcerated mucosa appear around the nadir.

Oral care is the daily intervention: a soft toothbrush or foam swab, bland rinses (saline or sodium bicarbonate per protocol), lip moisture, and removal of poorly fitting orthodontics as the team directs. Avoid alcohol-based rinses. Cryotherapy (ice chips or popsicles during selected short infusions such as bolus melphalan) is protocol-specific; do not invent it for every bag.

Palifermin (keratinocyte growth factor) appears on some adult HSCT mucositis-prevention pathways. It is rarely a pediatric first-line tool; do not treat it as a CPHON default for every child with mouth sores. "Magic mouthwash" (often a lidocaine–diphenhydramine–antacid combination) is institutional: know your recipe, the nothing-by-mouth window after viscous lidocaine in a toddler who might bite a numb tongue, and that it treats pain, not infection.

Pain control is not optional. Topical agents plus scheduled systemic analgesia, including opioids when mucositis grades prevent drinking, belong on the board. A child who will not swallow is already dehydrating.

Herpes simplex virus (HSV) versus chemotherapy mucositis: chemo mucositis is often symmetric, timed to the nadir, and involves movable mucosa. HSV more often crops as vesicular or ulcerative lesions on keratinized mucosa (lips, hard palate, gingiva) and may follow a cold-sore history. Swab when the picture is atypical, start antiviral therapy as ordered, and do not call every lip crack "just chemo." Candidal thrush is white plaques that scrape; nystatin or an azole as ordered is not HSV coverage.

Feeding during mucositis: offer cold, bland, non-acidic fluids; hold spicy, citrus, and rough crackers. Enteral nutrition (EN) via nasogastric or gastrostomy tube is preferred when the gut works. Parenteral nutrition (total parenteral nutrition, TPN) is reserved for ileus, severe gut mucositis, or when EN cannot meet needs. A 5-year-old who sips ice chips but will not chew is still a feeding patient, not a reason to wait until the mouth "looks pretty."

Chemotherapy-induced nausea and vomiting

Chemotherapy-induced nausea and vomiting (CINV) has three clocks:

• Acute: during the first 24 hours after the emetogenic dose.
• Delayed: after 24 hours, classic after cisplatin and some anthracycline or cyclophosphamide combinations; can last days.
• Anticipatory: learned, often triggered by clinic smells, the parking garage, or the sight of the chair, before the drug starts.

Antiemetic classes (generic names only):

• 5-hydroxytryptamine-3 (5-HT3) receptor antagonists: ondansetron, granisetron. Watch constipation and QTc with ondansetron, especially intravenous and with other QT-active drugs.
• Neurokinin-1 (NK1) receptor antagonists: aprepitant (and related agents). Aprepitant has cytochrome P450 (CYP) interactions—it can change levels of selected concurrent drugs, including some corticosteroids and other CYP3A4 substrates. Flag the medication list; do not add aprepitant as a casual extra.
• Dexamethasone is a backbone antiemetic on many moderate- and high-emetic regimens unless the protocol already uses high-dose steroids or there is a contraindication.
• Olanzapine appears on some adolescent and young adult (AYA) pathways for breakthrough or highly emetogenic CINV; sedation and metabolic effects are the watch. It is not a toddler default.
• Lorazepam treats anticipatory nausea as an anxiolytic adjunct, not as the sole antiemetic for cisplatin.

Match the regimen to emetogenicity and the clock. Acute ondansetron that stops at discharge will miss delayed cisplatin vomiting. Anticipatory vomiting on the car ride needs lorazepam plus a behavioral plan, not another 5-HT3 in the driveway. Breakthrough emesis is a call to add a drug from a different class, not to repeat the same 5-HT3 hourly without a team order.

Constipation, diarrhea, appetite, liver, and taste

Vincristine autonomic neuropathy and opioid analgesia both slow the gut. Start a bowel regimen (polyethylene glycol, senna as ordered) the day vincristine or scheduled opioids start. Do not wait for three days without stool. Distention, absent stool, and vomiting are ileus or obstruction until proven otherwise—signpost to the GI-emergency chapter rather than adding another stimulant at home.

Diarrhea has several pediatric oncology maps:

• Irinotecan early (cholinergic) diarrhea: during or within hours of infusion, often with flushing, cramping, and diaphoresis. Atropine as ordered is the rescue, not loperamide first.
• Irinotecan late diarrhea: days later, secretory; loperamide per order and hydration, with a low threshold to evaluate infection.
• Acute graft-versus-host disease (GVHD) of the gut after allogeneic HSCT: voluminous watery or bloody stool, cramping, anorexia.
• Infection, especially Clostridioides difficile (C. difficile) after antibiotics, and viral gastroenteritis.

Do not reflexively give loperamide in a neutropenic child with fever and right-lower-quadrant pain—that picture is typhlitis until the emergency workup says otherwise. Do not skip a C. difficile assay because "everyone has chemo diarrhea."

Anorexia and cachexia are not picky eating. Taste changes (dysgeusia)—metallic taste after platinum or after many cycles—make favorite foods fail. Small frequent offerings, cold foods, and nutrition-team calories matter. EN is first-line when the gut is usable; TPN is for gut failure, not for a child who simply prefers juice. Track weight and hydration.

Hepatic injury: methotrexate and mercaptopurine (6-MP) cause chemical hepatitis; hold or adjust per protocol when transaminases or bilirubin rise. Tender hepatomegaly, rapid weight gain, and jaundice after HSCT conditioning are sinusoidal obstruction syndrome / veno-occlusive disease (SOS/VOD)—signpost to the emergency chapter, not ordinary 6-MP hepatitis. Abdominal radiation adds chronic enteritis, lactose intolerance, and stricture risk as late effects. Teach families that "the stomach never recovered" can be a real late effect, not a behavior problem.