27.4 Pediatric GI Disorders & Poisoning: Vomiting (Pyloric Stenosis, Atresias, Malrotation, Intussusception, GERD), Diarrhea and IMCI Rehydration Plans, Abdominal Pain, Constipation & Hirschsprung, Jaundice, Biliary Atresia & Choledochal Cyst, Hepatitis, Food Allergy, and Kerosene, Aspirin and INH Poisoning

Why this area matters

The TOS GI competencies are to:

• identify the age, sex and racial predilection and the burden of GI disorders;
• reach a diagnosis and differential diagnosis;
• prioritize tests;
• recognize emergencies;
• manage the case and educate caregivers.

Diarrhea remains a leading cause of illness and death in Filipino children under 5. It is mostly preventable with safe water, sanitation, breastfeeding and rotavirus and measles vaccines, and treatable with ORS and zinc. Accidental kerosene and drug ingestions are common in homes where they are stored in soft-drink bottles or within reach.

Vomiting: congenital and acquired causes

Other causes of vomiting are infection (gastroenteritis, UTI, otitis, meningitis), raised intracranial pressure, DKA, inborn errors, poisoning and cow's milk protein allergy.

Diarrheal Illnesses and Dehydration Protocols

Diarrheal episodes are categorized into: (1) Acute Watery Diarrhea, (2) Dysentery (visible blood in stool), and (3) Persistent Diarrhea (lasting $\ge 14$ days).

Dehydration Assessment and Classification Matrix

Treatment Plans A, B, and C

Plan A: Treat Diarrhea at Home (No Dehydration)

1. Give Extra Fluids: Administer standard Oral Rehydration Salts (ORS) solution, rice water (am), coconut water, or clean water after each loose stool: $50-100\text{ mL}$ for age $< 2$ years; $100-200\text{ mL}$ for age $\ge 2$ years.
2. Zinc Supplementation: Administer elemental zinc for 10 to 14 days ($10\text{ mg/day}$ for infants $< 6$ months; $20\text{ mg/day}$ for age $\ge 6$ months). Zinc repairs gut mucosal architecture, reduces diarrhea duration and stool volume, and prevents recurrent episodes for 2 to 3 months.
3. Continue Frequent Feeding: Continue exclusive breastfeeding or age-appropriate feeding; never restrict food.
4. Teach Danger Signs: Advise mother to return immediately if the child develops: drinking poorly, increasing vomiting, blood in stool, or high fever.

Plan B: Treat Some Dehydration with ORS

• Administer Reduced Osmolarity ORS (osmolarity: $245\text{ mOsm/L}$; sodium: $75\text{ mmol/L}$, glucose: $75\text{ mmol/L}$) at a volume of $75\text{ mL/kg}$ over 4 hours.
• If weight is unknown: age $< 4$ months ($200-400\text{ mL}$); 4-11 months ($400-700\text{ mL}$); 12-23 months ($700-900\text{ mL}$); 2-4 years ($900-1400\text{ mL}$).
• Give frequent small sips with a cup and spoon. If the child vomits, wait 10 minutes and then resume at a slower pace.
• Reassess and reclassify dehydration status after 4 hours.

Plan C: Treat Severe Dehydration Rapidly with IV Fluids

• Fluid of Choice: Ringer's Lactate (or Normal Saline 0.9% NaCl if Ringer's is unavailable; 5% Dextrose is strictly contraindicated for volume resuscitation).
• Total Volume: $100\text{ mL/kg}$ IV divided into two phases:

• Reassess radial pulse and perfusion every 15 to 30 minutes. Give oral ORS ($5\text{ mL/kg/hour}$) as soon as the child can swallow.

Dysentery Management

• Defined as diarrhea containing visible gross red blood in stool.
• Primary etiology: Shigella flexneri or Shigella sonnei.
• Treatment: Oral Ciprofloxacin ($15\text{ mg/kg}$ BID for 3 days) as first-line empiric therapy. Metronidazole is indicated only if microscopic trophozoites of Entamoeba histolytica are confirmed.

Persistent diarrhea (14 days or more) is linked to malnutrition and lactose intolerance. It is managed with continued feeding (reduced lactose if needed), zinc, vitamin A and attention to nutrition. Antidiarrheal drugs and antiemetics such as loperamide are not used in young children.

Abdominal pain, distention and constipation

• Acute abdominal pain:
  • appendicitis, the most common surgical abdomen in older children; it perforates more often in young children because diagnosis is delayed;
  • intussusception;
  • mesenteric adenitis;
  • constipation;
  • UTI;
  • IgA vasculitis (Henoch-Schonlein purpura);
  • DKA;
  • testicular or ovarian torsion.
• Distention suggests obstruction, ascites, organomegaly, Hirschsprung disease or necrotizing enterocolitis in preterms.
• Functional constipation:
  • painful hard stools, withholding behavior, sometimes overflow soiling (encopresis);
  • management is disimpaction, osmotic laxatives (polyethylene glycol, lactulose), toilet training, fluids and fiber.
• Hirschsprung disease:
  • absence of ganglion cells in the distal colon;
  • delayed passage of meconium beyond 48 hours, chronic constipation from birth, abdominal distention and an explosive stool on rectal examination;
  • risk of enterocolitis;
  • diagnosed by rectal suction biopsy showing no ganglion cells;
  • treated by surgical pull-through.

Jaundice, hepatitis and liver disease

• Conjugated (direct) hyperbilirubinemia in an infant is always pathologic. Check any jaundice persisting beyond 2 weeks.
• Biliary atresia:
  • progressive fibrosis of the extrahepatic bile ducts;
  • jaundice after the first weeks, pale (acholic) stools, dark urine and hepatomegaly;
  • diagnosed by ultrasound, hepatobiliary scan and intraoperative cholangiogram;
  • Kasai portoenterostomy before about 60 days gives the best results, and transplantation may follow.
• Choledochal cyst:
  • cystic dilation of the bile ducts;
  • the classic triad is abdominal pain, jaundice and a right upper quadrant mass;
  • risks include cholangitis, pancreatitis and cholangiocarcinoma;
  • treated by excision with hepaticojejunostomy.
• Viral hepatitis:
  • hepatitis A is common, mild in young children and spread fecal-orally;
  • hepatitis B acquired at birth becomes chronic in about 90% of infants, which is why the birth-dose vaccine matters.
• Hepatosplenomegaly has many causes: infections (malaria, schistosomiasis, typhoid, EBV), hemolytic anemias such as thalassemia, storage diseases, leukemia and heart failure.
• Cirrhosis and ascites in children follow biliary atresia, chronic hepatitis B, Wilson disease and metabolic disease. Ascites is managed with salt restriction, diuretics and treatment of the cause.

Gastrointestinal food allergy

• Cow's milk protein allergy:
  • IgE-mediated forms cause urticaria, vomiting and anaphylaxis;
  • non-IgE forms include allergic proctocolitis (blood-streaked stools in a well breastfed infant), food protein-induced enterocolitis (repetitive vomiting, lethargy) and enteropathy;
  • management is elimination: the breastfeeding mother avoids dairy, or an extensively hydrolyzed or amino-acid formula is used. Most children outgrow it.
• Lactose intolerance is different: it is non-immune, with bloating and watery stools after lactose.

Poisoning: kerosene, aspirin and isoniazid

• General approach:
  • ABCs and glucose;
  • history of the agent, amount and time;
  • activated charcoal for some drugs within about 1 hour if the airway is protected;
  • no ipecac;
  • specific antidotes;
  • prevention through safe storage.
• Kerosene and other hydrocarbons:
  • the danger is aspiration chemical pneumonitis, from low viscosity and high volatility, even after small amounts;
  • cough, choking, tachypnea, fever and CNS depression;
  • X-ray changes may lag for hours;
  • do NOT induce vomiting or perform gastric lavage, and activated charcoal does not help;
  • give oxygen and supportive care; antibiotics and steroids are not routinely needed;
  • observe for at least 6 hours.
• Aspirin (salicylates):
  • tinnitus, vomiting, fever, hyperpnea;
  • early respiratory alkalosis, then high anion gap metabolic acidosis;
  • hypoglycemia, and in severe cases altered mental status;
  • treat with activated charcoal, fluids and IV sodium bicarbonate to alkalinize the urine (keeping potassium normal), plus glucose;
  • hemodialysis for very high levels, renal failure, pulmonary edema or CNS signs.
• Isoniazid:
  • an overdose of a TB drug found in many homes;
  • seizures refractory to usual anticonvulsants, metabolic acidosis and coma within hours;
  • the antidote is pyridoxine (vitamin B6), gram for gram of INH ingested (or 70 mg/kg if the amount is unknown), with benzodiazepines.
• Other common poisonings:
  • paracetamol: N-acetylcysteine guided by the level;
  • iron: deferoxamine;
  • organophosphates: atropine and pralidoxime.