17.2 Typhlitis

CPHON TCO V.A.2 tests typhlitis—neutropenic colitis, ileocecal inflammation—as an infectious gastrointestinal emergency. It is not the Domain IV mucositis and diarrhea lecture, not ordinary vincristine constipation, and not a reflex appendectomy. Recognition, first actions (nothing-by-mouth, bowel rest, broad antibiotics), and monitoring for perforation are the exam behaviors.

A 6-year-old on AML induction with an ANC of 80/µL, fever, right-lower-quadrant (RLQ) pain, and watery diarrhea; a 3-year-old who will not walk and draws the knees up rather than pointing to the belly; and a 15-year-old whose parent is about to give a constipation enema are typhlitis patients until the workup says otherwise.

What it is and who gets it

Typhlitis (named for the cecum) is inflammation and bacterial invasion of damaged bowel wall when neutrophils are essentially absent. Intensive induction—especially AML and other regimens that produce profound, prolonged neutropenia—injures mucosa. Cytarabine, anthracyclines, and other intensive blocks are classic. Organisms from the lumen, including gram-negatives and anaerobes, invade. The ileocecal region is the usual map, but the process can involve ileum or colon more broadly (neutropenic enterocolitis).

Recognition cluster:

• Fever in a child who is profoundly neutropenic.
• Abdominal pain, often RLQ, but toddlers may only show irritability, flexed hips, or refusal to walk. An adolescent can localize; a preschooler may not.
• Diarrhea, sometimes bloody.
• Distension, nausea, vomiting, and decreased bowel sounds.
• Peritoneal signs—rigidity, rebound, guarding—warn of perforation or full-thickness necrosis.

A child on AML induction with this cluster is typhlitis until imaging and the team say otherwise. Do not send that child home with loperamide. Do not treat isolated chemo diarrhea without examining the abdomen. Do not assume the 3-year-old who will not stand is being stubborn; a toddler with an acute abdomen often cannot point to McBurney's point.

Walk the AML night. Counts have been near zero for a week. The 6-year-old spiked 38.6°C, then vomited, then pointed to the right lower belly. Distension is new. This is not a stool softener problem. Keep the child nothing by mouth (NPO), obtain access, start the abdominal workup, and cover bowel organisms—including anaerobes—while the scanner is arranged.

Imaging, first actions, and what never goes in the rectum

Computed tomography (CT) with intravenous contrast if kidneys allow, or ultrasound (US), is the diagnostic picture: bowel-wall thickening, often ileocecal, with or without inflammatory stranding. Pneumatosis, portal venous gas, and free air mark a worse wall and possible perforation. US is attractive in children to limit radiation; a nondiagnostic US does not end the workup if the clinical picture is still typhlitis.

First actions are medical, and they start before the scanner:

• NPO and bowel rest.
• Intravenous fluids; nasogastric (NG) decompression if ileus and vomiting.
• Broad-spectrum antibiotics covering gram-negatives (including Pseudomonas) and anaerobes: piperacillin-tazobactam; cefepime plus metronidazole; or meropenem—as the protocol lists. FN monotherapy that lacks anaerobic coverage is not enough once typhlitis is the working diagnosis.
• Pain control that does not hide serial exams; the surgeon needs a comparable abdomen two hours from now.
• Surgical consult early if there is peritonitis, free air, uncontrolled bleeding, or deterioration on medical therapy. Many children recover with bowel rest and antibiotics as neutrophils return; surgery is for complications, not a trophy resection.
• Nutrition: parenteral nutrition if NPO will last; restart enteral feeding only when the team sees a quieter abdomen and rising counts.

Avoid rectal temperatures, suppositories, enemas, and digital rectal examinations in neutropenia. They can inoculate bacteria, worsen mucosal injury, and perforate fragile bowel. The parent who wants to clear the blockage with a phosphate enema is a teaching moment and a stop. Obtain stool for Clostridioides difficile (C. difficile) by a method that does not require rectal instrumentation; a carefully collected specimen is not an enema. The same no-rectal rule applies to the febrile neutropenic child without abdominal pain—TCO V.A.1 and V.A.2 share that safety line.

Monitoring is serial abdominal exams, vital signs, lactate as ordered, intake and output, and ANC trend. Clinical improvement often tracks neutrophil recovery. Sudden worsening, new rigidity, rising tachycardia, or free air is perforation—NPO stays NPO, and the surgeon is not optional. Colony-stimulating factors may be ordered to shorten neutropenia; they do not replace antibiotics or a surgical abdomen.

Differential: appendicitis, C. difficile, GVHD

Appendicitis can share RLQ pain and fever. In profound neutropenia, the safer CPHON frame is treat as typhlitis with medical management and imaging, and involve surgery, rather than rushing a neutropenic child to appendectomy because the pain is on the right. An appendix can be involved in neutropenic colitis; the operation is for perforation and peritonitis, not for a pretty RLQ.

C. difficile colitis follows antibiotics, produces watery or bloody diarrhea and cramping, and is diagnosed with stool testing. It can coexist with typhlitis. A positive toxin or nucleic-acid test does not let you ignore ileocecal wall thickening and an ANC of 40/µL, and a negative test does not forbid typhlitis. Do not give antidiarrheals that paralyze the colon until infection and typhlitis are addressed.

Acute graft-versus-host disease (GVHD) of the gut after allogeneic HSCT is voluminous watery or bloody stool, cramping, and anorexia, typically after engraftment, not on AML day 10 with an ANC of 0. Counts, timing, and focal RLQ peritonitis separate the maps. A 9-year-old on day +40 with an ANC of 1,800/µL and diffuse cramping is a transplant-team GVHD or infection workup, including C. difficile—not a default typhlitis label. Gut GVHD is still an emergency for that team; it is not named typhlitis solely because diarrhea occurred.

Intussusception and mechanical obstruction (the next section), hemorrhagic cystitis (genitourinary, not this belly), and ordinary mucositis without focal peritonitis complete the look-alikes. If the child is neutropenic, febrile, and tender in the RLQ, start the typhlitis pathway while you sort them. Do not wait for bloody stool to take the pain seriously. Do not treat RLQ peritonitis with a home bowel regimen from the gastrointestinal-effects chapter.

The CPHON product is an NPO sign, a beta-lactam that covers anaerobes, an abdomen reexamined before the next shift, a rectum that was never instrumented, and a surgeon who was called for peritonitis rather than for curiosity.