Clinical Assessment: 15-Year-Old Girl with Persistent Vomiting Post-Gastroenteritis

Summary of the Presentation

Step 1: Why Is the Vomiting Persisting?

Differential Diagnosis (Most to Least Likely)

1. Post-infectious Gastroparesis / Gut Dysmotility (Most likely)

• Vomiting triggered by eating/drinking
• No pain (unlike obstruction)
• Watery, non-bloody vomit (gastric contents)
• Background fatigue and body aches (systemic recovery phase)

2. Metronidazole-Induced Nausea/Vomiting (Important contributor)

"Common side effects are headache, nausea, dry mouth, and a metallic taste. Vomiting, diarrhea, and abdominal distress are experienced occasionally."

3. Persistent Viral/Bacterial Enteritis

4. Dehydration and Electrolyte Imbalance

5. Secondary Lactose Intolerance

6. Functional Nausea / Cyclic Vomiting Syndrome (CVS)

7. Raised Intracranial Pressure (Must not miss)

8. Pregnancy (In a 15-year-old female — always consider)

Immediate Red Flags to Assess

Recommended Investigations

1. Urine pregnancy test (hCG) — mandatory in any adolescent female with vomiting
2. Serum electrolytes (Na⁺, K⁺, Cl⁻, HCO₃⁻) — assess for hypokalemia, hypochloremic alkalosis from repeated vomiting
3. Blood urea nitrogen (BUN) / creatinine — renal function + dehydration status
4. Blood glucose — rule out DKA (nausea + fatigue + adolescent)
5. CBC — infection, anemia
6. Stool examination — if still loose or if parasites (Giardia, Cryptosporidium) suspected
7. Urine analysis — UTI as a co-precipitant
8. If headaches are prominent: fundoscopy and/or consider neuroimaging

Management Plan

A. Immediate Priorities

• Normal saline (0.9% NaCl) or Ringer's Lactate — 10–20 mL/kg bolus if signs of moderate dehydration
• Then maintenance + replacement of ongoing losses
• Add potassium once urine output is confirmed and if hypokalemia is confirmed

B. Antiemetic Therapy

C. Dietary Management

• Small sip ORS method: 5 mL every 5 minutes initially, increasing gradually
• If oral route fails → nasogastric tube continuous slow ORS infusion
• Avoid solid food until sustained oral fluids are tolerated
• Avoid dairy initially (secondary lactase deficiency risk)
• Bland, low-fat foods when reintroducing solids (rice, toast, banana)

D. Address the Headache and Body Aches

• May reflect electrolyte imbalance (esp. hyponatremia) or systemic viral illness recovery
• Paracetamol (acetaminophen) 15 mg/kg for symptom relief — avoid ibuprofen/NSAIDs in a dehydrated patient (renal vasoconstriction risk)
• If headache persists or worsens after fluid correction → further evaluation

When to Escalate / Hospitalize

• Cannot maintain oral hydration despite antiemetics → admit for IV fluids
• Signs of significant dehydration: sunken eyes, dry mucous membranes, reduced skin turgor, tachycardia, reduced urine output
• Neurological symptoms (progressive headache, confusion, visual changes)
• Vomiting lasts >2 weeks despite treatment

Summary for the Clinician

1. Exclude pregnancy (urine hCG)
2. Correct dehydration with IV fluids
3. Check electrolytes
4. Start ondansetron as antiemetic
5. Reassess need for continued metronidazole
6. Graded oral rehydration when tolerated

Step-by-Step Management

15-Year-Old Girl — Persistent Vomiting After Gastroenteritis (1 Week)

STEP 1 — TRIAGE & RAPID CLINICAL ASSESSMENT

This patient is likely moderate dehydration — barely tolerating fluids for 48 hours is a red flag.

STEP 2 — URGENT INVESTIGATIONS (run in parallel)

If headaches worsen or neurological signs emerge: → fundoscopy and consider CT/MRI head to exclude raised ICP.

STEP 3 — STOP OR REASSESS METRONIDAZOLE

• Metronidazole causes nausea and vomiting in ~30% of patients (Sleisenger & Fordtran)
• Symptoms include: nausea, vomiting, headache, metallic taste, abdominal distress — matching this patient exactly
• The diarrhea has resolved → the original indication may be fulfilled
• Action: Discuss with prescribing physician — if the course is complete or the indication resolved, stop metronidazole

STEP 4 — REHYDRATION

If moderate dehydration (most likely scenario):

• Use WHO-ORS or a commercial ORS (Pedialyte / equivalent)
• Give small volumes: 5 mL every 2–5 minutes initially
• Increase gradually as tolerated
• Target: 50–100 mL/kg over 4 hours + 10 mL/kg per vomiting episode as ongoing replacement
• Do NOT give plain water, juices, or soft drinks (inadequate electrolytes)

• IV fluids: Normal saline (0.9% NaCl) or Ringer's Lactate
  • Bolus: 10–20 mL/kg over 20–30 minutes if moderate-severe dehydration
  • Then maintenance + replacement of ongoing losses
• OR Nasogastric ORS: 50 mL/kg over 3 hours — equally effective as IV, useful when IV access is difficult
• Add KCl to IV fluids only after urine output is confirmed and hypokalemia is documented on labs

STEP 5 — ANTIEMETIC THERAPY

First-line: Ondansetron (5-HT₃ antagonist)

"Ondansetron may be used as an adjunct to ORT in children with persistent vomiting at a dose of 0.15 mg/kg/dose PO" — Tintinalli's Emergency Medicine

• If gastroparesis/gut dysmotility is the primary mechanism and ondansetron alone is insufficient: Domperidone 10 mg TID (prokinetic with less CNS penetration) is a reasonable add-on in adolescents.

STEP 6 — DIETARY REINTRODUCTION

1. Start with sips of ORS only — 5 mL every 5 minutes
2. Progress to 30 mL every 15 minutes as tolerated
3. Once ORS tolerated for 2+ hours → introduce bland solids:
   • Rice, dry toast, boiled potato, banana
   • Small amounts, every 2–3 hours
4. Avoid initially:
   • Dairy products (secondary lactose intolerance risk post-gastroenteritis)
   • Fatty/fried food (delays gastric emptying)
   • Fizzy drinks (gastric distension → worsens nausea)
5. Resume normal diet gradually once tolerating solids × 24 hours

STEP 7 — TREAT ASSOCIATED SYMPTOMS

STEP 8 — MONITOR & REASSESS

• Is she tolerating oral fluids? → Continue ORT, advance diet
• Has vomiting frequency reduced? → Continue antiemetic as needed
• Are vitals improving (HR normalizing)? → Signs of adequate rehydration
• Urine output returning? → Reassuring sign

• Urine output ≥ 1 mL/kg/hour
• Moist mucous membranes
• Improving alertness and energy
• Heart rate normalizing

STEP 9 — DECISION: ADMIT OR DISCHARGE?

Discharge home if:

• Tolerating oral fluids after treatment
• No significant electrolyte abnormality
• Pregnancy test negative
• Caregiver understands ORS technique
• Safety net: return if cannot keep fluids down, worsening headache, or no urine output in 8 hours

Admit to hospital if:

• Cannot sustain oral fluids despite antiemetic + ORT attempt
• Significant electrolyte disturbance (K⁺ < 3.0, Na⁺ < 130)
• Severe dehydration with hemodynamic compromise
• Worsening or persistent headache → neurology review
• Pregnancy confirmed → obstetric consult

STEP 10 — FOLLOW-UP PLAN (5–7 Days)

• Review stool cultures if sent — treat specific pathogen if found
• If vomiting continues beyond 2 weeks despite all above:
  • Consider gastric emptying study (scintigraphy) to confirm gastroparesis
  • Refer to pediatric gastroenterology
  • Consider cyclic vomiting syndrome if episodic pattern emerges
• Reassess nutritional status — if intake remains poor, consider nutritional support

Quick Reference Summary

1. Assess dehydration severity
2. Investigations: hCG, electrolytes, glucose, CBC, renal function, urine
3. STOP metronidazole if course complete
4. Rehydrate: ORS 5 mL q2-5 min → escalate to IV/NG if needed
5. Ondansetron 0.15 mg/kg PO (≈4 mg) — single dose first line
6. Diet: ORS → bland solids → normal diet progressively
7. Paracetamol for headache/body aches (NO NSAIDs)
8. Monitor vitals, urine output, vomiting frequency at 4 hours
9. Discharge vs. admit based on response
10. Follow-up: if vomiting >2 weeks → gastric emptying study + GI referral