History Taking · Intermediate · Paediatrics

Projectile Vomiting in Infant - Progressive Feeding Difficulty

Practise this PLAB 2 history taking station on Pyloric Stenosis. 8-minute voice AI simulation with feedback on all 3 marking domains.

Clinical scenario

You are an FY2 doctor in the paediatric clinic. You see Ronan, a five-week-old boy, brought by his mother Rachel with a history of progressive projectile vomiting starting one week ago. He appears hungry after vomiting and his mother is concerned about dehydration and feeding. Please take a focused history, perform an appropriate examination, and discuss investigation and management.

Background notes: PMH: Nil significant

What this station tests

  • Classic pyloric stenosis pattern: projectile non-bilious vomiting, hungry immediately after, progressive, male infant 3-5 weeks
  • Non-bilious is critical: bilious (green) vomiting suggests distal obstruction (malrotation) which is a different emergency
  • Hypochloraemic hypokalaemic metabolic alkalosis: the metabolic consequence of gastric acid loss
  • USS as the diagnostic investigation: thickened pylorus confirmed on ultrasound
  • Electrolyte correction before surgery: anaesthesia is unsafe with uncorrected metabolic alkalosis

How to use your 8 minutes

  • 0-1 min — Introduction: Introduce yourself, confirm identity, open question. 'What's brought you in today?'
  • 1-4 min — Systematic History: Presenting complaint detail (SOCRATES for pain, timeline, severity). Systems review. PMH, medications, allergies.
  • 4-6 min — Context and ICE: Social history (smoking, alcohol, occupation, living situation). Family history. Ideas, Concerns, Expectations.
  • 6-7 min — Summary and Plan: Summarise findings back to patient. Share differential/working diagnosis. Outline investigation and management plan.
  • 7-8 min — Closing: Safety netting with specific red flags. Arrange follow-up. Check for questions.

Consultation approach

The opening

Projectile vomiting in a 3 to 5-week-old male infant is pyloric stenosis until proven otherwise. The candidate must identify the classic pattern: projectile (not just possetting), hungry immediately after vomiting, and progressive worsening. Ronan is 5 weeks old, first-born male, with 1 week of worsening projectile vomiting. Open with: 'Rachel, tell me about the vomiting and how Ronan has been feeding.'

Core approach

Classic pattern. Projectile vomiting (forceful, travels a distance) shortly after feeds. Non-bilious (white or curdled milk, not green, which would suggest intestinal obstruction distal to the ampulla). He is immediately hungry after vomiting ('hungry vomiter'). Progressive worsening over 1 week (not improving). Weight loss or poor weight gain. He may be dehydrated (dry nappies, sunken fontanelle, reduced skin turgor).

Demographics fit: male (4:1 ratio), first-born, age 5 weeks (peak 3 to 5 weeks). Ask about family history: pyloric stenosis has a genetic component.

Distinguish from other causes of infant vomiting. GORD: possetting (effortless, small volumes, not projectile). Overfeeding: volumes too large, not projectile. Intestinal obstruction: bilious (green) vomiting would suggest malrotation or other obstruction (a surgical emergency). Infection: fever, diarrhoea, systemically unwell. The non-bilious, projectile, progressive pattern with a hungry infant is diagnostic.

Assess dehydration and metabolic status. Pyloric stenosis causes hypochloraemic hypokalaemic metabolic alkalosis from gastric acid loss. Check nappy output, weight trend, fontanelle.

Closing and safety netting

This needs urgent hospital referral. 'Rachel, the pattern of vomiting you describe, projectile, getting worse, and Ronan wanting to feed immediately after, is very typical of a condition called pyloric stenosis. This is where the muscle at the outlet of his stomach has thickened and is preventing milk passing through.' Reassure: 'This is very common and very treatable with a small operation.'

Urgent paediatric surgical referral. Diagnosis confirmed by USS (thickened pylorus, 'olive' sign on examination if palpable). Treatment: Ramstedt's pyloromyotomy (a small operation to divide the thickened muscle). Before surgery: IV fluid resuscitation and electrolyte correction (the metabolic derangement must be corrected before anaesthesia). Safety net: if he stops feeding, becomes very drowsy, or has no wet nappies, go to A&E immediately.

How examiners mark this station

Examiners will focus on the thoroughness and structure of your history taking for pyloric stenosis. Domain 1 (Data Gathering) carries the most weight: expect marks for systematic coverage of presenting complaint, red flags, PMH, medications, social and family history. Domain 2 (Clinical Management) requires a clear differential, appropriate investigations, and a safe management plan with safety netting. Domain 3 (Interpersonal Skills) is assessed throughout: genuine exploration of ICE, active listening, empathic responses, and clear communication without jargon.

Domain 1: Data Gathering, Technical and Assessment Skills (Primary focus)

Scores well: Projectile pattern confirmed. Non-bilious vomit established. Hungry after vomiting. Dehydration assessed. Demographics fit (male, first-born, 5 weeks). Weight trend checked.

Costs marks: Not confirming projectile. Not checking vomit colour. Not assessing dehydration.

Domain 2: Clinical Management Skills (Primary focus)

Scores well: Urgent paediatric surgical referral. USS as diagnostic test. Ramstedt's pyloromyotomy as treatment. Electrolyte correction before surgery. Dehydration management.

Costs marks: Not referring urgently. Not knowing the treatment. Not mentioning electrolyte correction.

Domain 3: Interpersonal Skills (Throughout)

Scores well: Reassuring about treatability ('very common, very treatable'). Explaining the condition in simple terms. Acknowledging the mother's distress. Clear safety netting.

Costs marks: Being alarmist. Not reassuring about outcomes. Not explaining what happens next.

Common examiner feedback (and how to fix it)

Did not gather sufficient information to make an adequate assessment of the patient's condition

Fix: Use a consistent framework for every history. After covering the presenting complaint, systematically move through PMH, drug history, social history, family history, and ICE. Keep a mental checklist.

Did not identify the patient's problems and/or did not develop a management plan adequately

Fix: Reserve the final 2 minutes to summarise your findings, share your working diagnosis with the patient, and outline your investigation and management plan including safety netting.

Common mistakes in this station

  1. Not distinguishing projectile from possetting. GORD causes effortless small-volume regurgitation. Pyloric stenosis causes forceful, projectile vomiting that travels a distance. Candidates who do not clarify this miss the diagnostic feature.
  2. Not checking for bilious vomiting. Green (bilious) vomiting in a neonate is malrotation until proven otherwise and is a surgical emergency. Candidates must specifically ask about the colour of the vomit.
  3. Not assessing dehydration. A vomiting infant can become dangerously dehydrated quickly. Candidates who refer without assessing hydration status miss the urgency of fluid resuscitation.

Resitting PLAB 2?

If you have previously struggled with history taking stations, focus on building a consistent systematic framework that you apply to every case. Practise structuring your history into clear phases (presenting complaint, systems review, PMH, social, ICE) so that even under pressure, you cover all domains. Many resitters lose marks not on knowledge but on organisation and time management.

Example opening

Good morning/afternoon, my name is Dr [Name], I'm one of the doctors here today. Could I confirm your name and date of birth please? Thank you. So, what's brought you in to see me today?

Frequently asked questions

How should I structure the pyloric stenosis history in this PLAB 2 station?

Projectile vomiting in a 3 to 5-week-old male infant is pyloric stenosis until proven otherwise. The candidate must identify the classic pattern: projectile (not just possetting), hungry immediately after vomiting, and progressive worsening. Ronan is 5 weeks old, first-born male, with 1 week of worsening projectile vomiting.

What are examiners marking in this pyloric stenosis station?

Marks are won for: Projectile pattern confirmed. Non-bilious vomit established. Hungry after vomiting. Dehydration assessed. Demographics fit (male, first-born, 5 weeks). Weight trend checked. Marks are lost for: Not confirming projectile. Not checking vomit colour. Not assessing dehydration.

What is the most common mistake candidates make in this pyloric stenosis station?

Not distinguishing projectile from possetting. GORD causes effortless small-volume regurgitation. Pyloric stenosis causes forceful, projectile vomiting that travels a distance.

How do I prepare for this station if I have not managed pyloric stenosis in clinical practice?

Structure beats experience here. Focus on non-bilious is critical: bilious (green) vomiting suggests distal obstruction (malrotation) which is a different emergency. Work through the consultation approach above, then rehearse it aloud under the 8-minute time pressure so the structure holds up in the exam.

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