12.3 Acute Diarrhea, Celiac Disease & IBD Red Flags

Acute diarrhea is hours-on-site primary care. Celiac disease and IBD are the chronic GI diagnoses you recognize, test at a screening level, and refer. Clinical category #5 still scores assessment and management against NASPGHAN/AAP and CDC hydration rules — not adult traveler’s-diarrhea scripts.

Quick Answer: Mild–moderate dehydration from AGE gets ORS first; ondansetron is for selected children whose vomiting blocks ORS. Do not give antimotility drugs to young children. Bloody diarrhea raises STEC (E. coli O157) — avoid antibiotics because they increase HUS risk. Celiac testing is IgA tTG plus total IgA while gluten is still in the diet, then GI. IBD red flags and growth failure go to GI; the CPNP-PC does not start biologics.

Acute gastroenteritis: replace fluid, do not paralyze the gut

Most pediatric AGE is viral. Diagnosis is clinical: vomiting and/or diarrhea, often with low-grade fever and sick contacts. The management question is hydration, not which virus name you print on the after-visit summary.

Oral rehydration solution (ORS) is first-line for mild and moderate dehydration. Glucose–sodium cotransport still works in viral enteritis. Use a reduced-osmolarity ORS. Apple juice is not the ideal sodium source for an infant; a sports drink is not a WHO-style ORS. Give small, frequent volumes. Continue breastfeeding. Resume an age-appropriate diet early — do not impose a prolonged clear-liquid or BRAT-only week.

Ondansetron (orally dissolving) is selected, not universal: a single dose in a child whose vomiting blocks ORS, so you can hydrate orally and avoid an IV. It is not a discharge souvenir for every spit into a basin.

Avoid antimotility agents (loperamide) in young children. They do not treat the infection, they can cause ileus and opioid-like toxicity, and they are the wrong move in bloody or suspected STEC diarrhea. Leftover adult antidiarrheals are not a toddler plan.

Daycare: keep the child out until fever is gone and stool is contained per public-health rules. Bloody diarrhea stays home until the child is cleared. You do not need a multiplex stool PCR on every 36-hour watery illness in a well, hydrating preschooler. Test when there is blood, severe or prolonged disease, travel, an outbreak or daycare cluster, young infancy, or immunocompromise.

Bloody diarrhea and HUS

Watery diarrhea that becomes frankly bloody, often with abdominal pain out of proportion and little or no fever, is Shiga toxin–producing E. coli (STEC) — classically O157:H7 — until you have a better explanation. The feared extra-intestinal complication is hemolytic uremic syndrome (HUS): microangiopathic hemolytic anemia, thrombocytopenia, and acute kidney injury (oliguria, rising creatinine, hypertension, pallor, petechiae).

Antibiotics and antimotility agents are associated with increased HUS risk in STEC (increased Shiga-toxin release in a stalled gut). Primary-care moves: supportive care, close hydration, do not prescribe antibiotics for suspected STEC, do not give loperamide, arrange follow-up that can catch HUS (CBC, smear, renal function, urine output), and involve public health. Campylobacter, Salmonella, and Shigella have different antibiotic rules — do not shotgun a macrolide into bloody diarrhea “just in case” when the story is STEC.

Toddler’s diarrhea

Chronic nonspecific diarrhea of childhood (toddler’s diarrhea) is frequent loose stools, often with undigested food particles, in a well-growing child roughly 6 months to 5 years who drinks a lot of juice or sweet drinks (fructose, sorbitol). There is no blood, no nocturnal stooling, no anemia, and no failure to thrive. Treatment is dietary: cut juice, increase fat and fiber, normalize meal structure. It is not IBD, not celiac until alarm features appear, and not an indication for chronic loperamide.

Celiac disease

Celiac disease is immune-mediated enteropathy triggered by gluten in genetically susceptible children (HLA-DQ2/DQ8). It presents as diarrhea and bloating — and also as constipation, FTT, iron-deficiency anemia, delayed puberty, elevated transaminases, dermatitis herpetiformis, or silent disease in a screened relative or a child with type 1 diabetes or Down syndrome.

Testing rules the CPNP-PC must not break:

1. The child must still be eating gluten. A parent-initiated gluten-free diet falsely lowers tTG. If already off gluten, a supervised gluten challenge before serology is the honest path (pediatric GI helps).
2. Order IgA tissue transglutaminase (tTG-IgA) plus total serum IgA. Total IgA catches IgA deficiency, which otherwise yields a falsely negative tTG-IgA. If IgA is deficient, use IgG-based tests (DGP-IgG or tTG-IgG).
3. Positive serology → pediatric GI. In US primary-care pediatric practice, endoscopic biopsy while on gluten remains the confirmatory pathway the NP should expect. Do not start a lifelong gluten-free diet on a weakly positive tTG and a hope.
4. Screen associated groups (type 1 diabetes, Down syndrome, Turner syndrome, first-degree relatives, IgA deficiency) — still on gluten.

Once diagnosed, a gluten-free diet with GI and a dietitian is the treatment — not a primary-care “try gluten-free for a month and see.”

IBD red flags — refer; do not start biologics

Inflammatory bowel disease (Crohn disease, ulcerative colitis) presents with chronic diarrhea, blood, nocturnal stools, growth failure, delayed puberty, abdominal pain, anemia, hypoalbuminemia, elevated CRP/ESR, a high fecal calprotectin, and perianal Crohn disease. Family IBD raises concern. The CPNP-PC recognizes, obtains screening labs, and refers. You do not initiate biologics, immunomodulators, or a solo systemic-steroid IBD induction from the primary-care closet. Those drugs belong to pediatric GI after endoscopy. Watching the height percentile fall for another year is not conservative care.

Lactose intolerance versus milk-protein allergy

Post-infectious lactose intolerance is real and temporary after AGE. Do not lock a 9-month-old onto a permanent gluten-free, dairy-free, untested diet because a rotavirus week was messy.

Dehydration assessment

Assess perfusion and water, not how many times the caregiver counted diarrhea.

Severe dehydration, shock, altered mental status, intractable vomiting, suspected surgical abdomen, or suspected HUS: emergency isotonic IV (or IO) fluid, not another hour of ORS experiments in the hallway. Mild–moderate: ORS in clinic or at home with return precautions — no tears, no wet diaper, lethargy, bilious emesis, or blood.

Exam traps. Antibiotics for STEC. Loperamide in toddlers. An IV for every watery stool in an alert, tearing child. tTG drawn on a gluten-free diet. Starting infliximab from primary care. Calling CMPA “lactose intolerance” and using lactose-free cow’s milk formula. Missing absent tears, oliguria, and delayed cap refill because the parent says the child “still drinks juice.”