Eduovisual
Pediatrics (System-Integrated)
Pyloric stenosis: diagnosis and management
— Incidence ~2–4 per 1,000 live births in the US
— First-born male infants of European ancestry most classically affected (M:F ~4:1)
— Familial clustering: risk markedly increased if mother had HPS as an infant
— Macrolide exposure in neonates (erythromycin > azithromycin), especially in the first 2 weeks of life
— Maternal macrolide use during late pregnancy or breastfeeding
— Bottle feeding, formula feeding, transpyloric feeding
— Preterm birth (shifts presentation later in chronologic age)
— Previously well full-term infant, 4–6 weeks old, with progressive nonbilious projectile vomiting after every feed
— Infant remains hungry ("hungry vomiter") and eagerly refeeds
— Weight loss or failure to regain birth weight, decreased wet diapers
— Constipation, hypochloremic hypokalemic metabolic alkalosis on incidental labs
— Pyloric stenosis is the most common surgical cause of vomiting in infancy
— Delay leads to dehydration, electrolyte derangement, aspiration, and failure to thrive
— Early recognition in the outpatient clinic prevents ED-level decompensation
Board pearl: A 5-week-old first-born boy with nonbilious, projectile vomiting, eager to refeed, and a recent course of oral erythromycin for pertussis prophylaxis is the prototypical Step 3 stem — order an abdominal ultrasound, not an upper GI series, as the first imaging step.
Step 3 management: In clinic, do not send the infant home with reassurance; arrange same-day ED evaluation for IV fluids, electrolytes, and ultrasound confirmation before surgical referral.
— Begins as occasional spit-up, progresses over days to forceful projectile emesis ejecting feet from the infant
— Occurs immediately after or during feeds
— Vomitus may be blood-streaked or coffee-ground (gastritis from retained acid) in ~10%
— Never bilious — bilious emesis suggests malrotation/volvulus and demands emergent surgical evaluation
— Classic "hungry vomiter": infant feeds vigorously, vomits, then immediately wants to feed again
— Contrast with viral gastroenteritis (anorexia) or sepsis (poor feeding)
— Symptoms typically begin 2–8 weeks of life, peak at 3–6 weeks
— Preterm infants present later by chronologic age but similar postmenstrual age
— Weight loss or failure to gain since birth
— Decreased stool frequency and volume, small "starvation stools"
— Fewer wet diapers, increased sleepiness as dehydration progresses
— May have jaundice ("icteropyloric syndrome") from decreased glucuronyl transferase activity due to caloric deprivation — resolves after pyloromyotomy
— Ask specifically about neonatal macrolide use (erythromycin for pertussis exposure or chlamydial conjunctivitis prophylaxis)
— Maternal macrolide use during the third trimester or while breastfeeding
— Parental or sibling history of pyloric stenosis substantially increases risk
— Maternal history of HPS confers ~20% risk to male offspring
Key distinction: GERD vs pyloric stenosis — both cause postprandial vomiting in a young infant, but GERD vomiting is effortless and non-projectile, infant is happy and gaining weight, and it improves with positioning and feeding adjustments. Projectile vomiting with weight loss is never physiologic GERD.
Board pearl: Always document bilious vs nonbilious character of emesis in any vomiting infant — it dictates whether you image with ultrasound (HPS) or get an emergent upper GI series (malrotation).
— Alert but dehydrated infant: dry mucous membranes, sunken anterior fontanelle, decreased skin turgor, prolonged capillary refill
— In advanced cases: lethargy, weak cry, weight below birth weight
— Visible left-to-right peristaltic waves across the upper abdomen after feeding (gastric peristalsis trying to push past obstruction)
— Palpable pyloric mass in the right upper quadrant or epigastrium, firm, mobile, ~1–2 cm, olive-shaped
— Best felt after the stomach is decompressed (NG suction or after the infant vomits) with the infant calm/feeding sucrose
— Sensitivity has fallen to <20% in modern practice because ultrasound is obtained earlier, before the olive matures
— Specificity remains very high — a definitively palpated olive can obviate imaging at experienced centers
— Tachycardia, weak peripheral pulses, cool extremities suggest hypovolemic shock — uncommon but possible with delayed presentation
— Weigh the infant naked on the same scale as prior visits; quantify percent weight loss from birth or last weight
— Estimate dehydration severity: mild (<5%), moderate (5–10%), severe (>10%) — drives fluid resuscitation strategy
— Scaphoid abdomen between feeds, fullness after feeds
— Mild jaundice in ~5% (indirect hyperbilirubinemia)
— No fever, no peritoneal signs — presence of either should prompt search for alternative diagnosis (sepsis, NEC, malrotation)
— No abdominal distension, no bilious vomiting, no bloody stools, no rebound/guarding
CCS pearl: On the CCS interface, your first orders for a suspected HPS infant should be NPO, IV access, vital signs, weight, basic metabolic panel, and abdominal ultrasound — before surgical consult, because surgery will not operate until electrolytes are corrected.
Board pearl: A palpable olive is pathognomonic — but its absence does not exclude HPS; image with ultrasound.
— Hypochloremic, hypokalemic metabolic alkalosis
— Mechanism: loss of HCl in vomitus → ↑ serum HCO₃⁻; volume depletion → aldosterone → renal K⁺ and H⁺ wasting
— Late finding: paradoxical aciduria (urine pH <6 despite alkalemia) as the kidney prioritizes Na⁺/volume retention over H⁺ excretion
— Severity of alkalosis correlates with duration of vomiting; earlier presentations may have normal labs
— Bilirubin: mild indirect hyperbilirubinemia in ~5% (icteropyloric syndrome)
— Glucose: hypoglycemia possible from poor intake and depleted glycogen stores
— CBC: usually unremarkable; hemoconcentration if severely dehydrated
— Blood gas (venous): confirms alkalosis, guides fluid management
— Diagnostic criteria (the "π" rule of thumb):
— Pyloric muscle thickness ≥3 mm (single wall)
— Pyloric channel length ≥15–17 mm
— Non-relaxing, elongated pyloric channel; failure of gastric contents to pass
— Real-time observation shows hyperperistaltic stomach with retained fluid
— Sensitivity and specificity >95% in experienced hands
— No radiation, no contrast, bedside-capable — ideal for infants
— Used only if ultrasound is equivocal or if malrotation is in the differential
— Findings: "string sign" (thin barium tract through narrowed channel), "shoulder sign" (mass indenting antrum), "double-track sign"
— Disadvantage: radiation, contrast aspiration risk, slower
Board pearl: Memorize the ultrasound "π/pi" mnemonic — Pyloric muscle ≥3 mm, Length ≥15 mm (3 + 14 ≈ π is a stretch; just remember 3 and 15).
Step 3 management: Order CMP, blood gas, and abdominal ultrasound simultaneously — do not delay surgical referral waiting on imaging, but do not operate until Cl⁻ >100, HCO₃⁻ <30, K⁺ normalized.
— Pyloric thickness 2–3 mm with concerning history → repeat ultrasound in 24–48 hours; pylorospasm can mimic but resolves, true HPS progresses
— Operator-dependent: ensure a pediatric radiologist or experienced sonographer
— Indications:
— Negative or equivocal ultrasound with persistent clinical suspicion
— Suspicion for malrotation, antral web, or duodenal stenosis
— Atypical age (>3 months or <2 weeks)
— Classic radiographic signs:
— String sign: thin column of contrast through narrow elongated pyloric channel
— Double-track sign: two parallel streaks of contrast in compressed mucosal folds
— Shoulder sign: bulging hypertrophied muscle indenting gastric antrum
— Mushroom sign / pyloric teat
— Provides functional assessment of gastric emptying
— Rarely indicated; reserved for ruling out antral web, peptic stricture, or mucosal disease in atypical cases
— Not diagnostic but may show distended air-filled stomach with paucity of distal gas ("single bubble" with minimal distal air, distinct from duodenal atresia's "double bubble")
— Useful primarily to exclude perforation or alternative pathology
— Recheck electrolytes every 4–6 hours during resuscitation until normalized
— Target preoperative parameters:
— Chloride >100 mEq/L
— Bicarbonate <30 mEq/L
— Potassium >3.5 mEq/L (and normal)
— Adequate urine output (>1–2 mL/kg/hr)
Key distinction: Pylorospasm is a functional mimic — ultrasound shows transient thickening that resolves on repeat scan; symptoms self-limit. True HPS shows progressive measurements and progressive symptoms.
Board pearl: If the vignette gives a double bubble sign, think duodenal atresia (presents day 1–2 of life with bilious vomiting and Down syndrome association) — not HPS.
— Surgery is never the first step — electrolyte and volume correction precede pyloromyotomy
— Operating on an alkalotic infant risks postoperative apnea (central respiratory depression from persistent CSF alkalosis depressing the medullary chemoreceptors)
1. NPO — stop all oral intake
2. NG decompression — only if significant gastric distension or ongoing vomiting; not routine
3. IV access — peripheral, two if dehydration is moderate-severe
4. Fluid resuscitation — see chunk 7
5. Electrolyte correction — Cl⁻, K⁺, HCO₃⁻ targets
6. Surgical consultation — pediatric surgery early, but operation deferred until labs corrected
— Mild (<5% dehydration, normal electrolytes): admit, IV fluids, surgery within 12–24 hours
— Moderate (5–10%, mild alkalosis): aggressive resuscitation, recheck labs q4–6h, surgery in 24–48 hours
— Severe (>10%, profound alkalosis, HCO₃⁻ >35): PICU-level care, slow correction over 24–72 hours to avoid rapid shifts
— All confirmed HPS infants are admitted
— Most centers admit to pediatric surgery service with co-management by hospitalist or PICU based on severity
— Reassure: pyloromyotomy is curative with excellent outcomes
— Expected length of stay: 24–48 hours postoperatively
— Vomiting may persist for a few feeds after surgery — does not indicate failure
Step 3 management: When the stem asks "what is the next best step" in a confirmed HPS infant with HCO₃⁻ of 34 and Cl⁻ of 88 — the answer is IV fluid resuscitation with electrolyte correction, not surgical consultation, not pyloromyotomy.
Board pearl: "Resuscitate, then operate" is the single most testable principle of HPS management.
— Phase 1 — Bolus (if hemodynamically unstable or >10% dehydrated):
— 20 mL/kg normal saline IV over 20–30 minutes
— Repeat once if perfusion remains poor
— Reassess perfusion, urine output, mental status
— Phase 2 — Rehydration and correction:
— D5 ½NS with 20–40 mEq/L KCl at 1.5–2× maintenance rate
— Add potassium only after urine output is established (>1 mL/kg/hr)
— Dextrose prevents hypoglycemia in the fasted infant
— Phase 3 — Maintenance until surgery:
— Continue D5 ¼NS or D5 ½NS with K⁺ at maintenance once labs corrected
— Chloride ≥100 mEq/L — most important single marker
— Bicarbonate <30 mEq/L (ideally <26)
— Potassium 3.5–5.0 mEq/L
— Sodium normalized
— Adequate urine output and resolved clinical dehydration
— Persistent hypochloremia perpetuates paradoxical aciduria and metabolic alkalosis
— Chloride repletion (via NS) allows the kidney to excrete bicarbonate and normalize pH — without it, alkalosis persists despite volume restoration
— Lactated Ringer's — contains lactate that converts to bicarbonate, worsening alkalosis
— Hypotonic fluids alone initially — risk of hyponatremia and inadequate chloride replacement
— Bicarbonate-containing fluids
— Oral feeds until post-pyloromyotomy
— Vital signs q1–2h
— Strict intake/output with urine output goal >1–2 mL/kg/hr
— Electrolytes q4–6h until target met, then q8–12h
— Daily weights
— Continuous pulse oximetry; apnea monitoring if severe alkalosis
CCS pearl: On CCS, the order set for HPS is: NPO, IV NS bolus 20 mL/kg, then D5 ½NS + 20 mEq/L KCl at 1.5× maintenance, CMP q6h, strict I/Os, daily weight, pediatric surgery consult.
Board pearl: Do not give potassium until the infant urinates.
— Longitudinal incision through the serosa and hypertrophied muscle of the pylorus, sparing the mucosa
— Performed only after electrolyte/volume correction
— Laparoscopic approach preferred in most US centers
— Shorter time to full feeds, less postoperative emesis, smaller scar
— Equivalent outcomes to open in skilled hands
— Open approach via right upper quadrant or periumbilical incision still common and effective
— General endotracheal anesthesia with rapid sequence induction
— NG tube placement and gastric decompression before induction (full-stomach precaution despite NPO)
— Avoid prolonged hyperventilation — exacerbates residual alkalosis and risks postoperative apnea
— Mucosal perforation (1–3%) — typically at the duodenal end where mucosa balloons into the myotomy; recognized by air/methylene blue insufflation, repaired primarily, may require omental patch
— Incomplete myotomy — persistent obstruction post-op, may require reoperation
— Feeds typically resumed within 4–8 hours (ad lib or structured advancement; ad lib non-inferior)
— Postoperative vomiting occurs in 50–80% for the first few feeds — usually self-limited from mucosal edema and residual gastritis
— Persistent vomiting beyond 5–7 days warrants imaging to exclude incomplete myotomy
— IV fluids weaned as PO intake established
— Discharge typically within 24–48 hours of surgery
— IV atropine then oral, induces pyloric relaxation
— ~75–85% success rate, prolonged hospitalization (1–3 weeks)
— Reserved for infants who are poor surgical candidates (rare) or in settings without pediatric surgical access
— Not first-line in the US
Board pearl: Mucosal perforation detected intraoperatively is repaired immediately; if missed and presenting postoperatively as peritonitis/fever/bilious drainage, requires urgent return to the OR.
Step 3 management: Postop infant vomiting once or twice in the first 24 hours — continue advancing feeds; only escalate workup if vomiting persists beyond several days.
— Chronologic age of presentation is later (often 6–12 weeks) but postmenstrual age remains similar (~42–48 weeks)
— Lower threshold for ultrasound in any preterm infant with persistent nonbilious vomiting
— Pyloric muscle thickness criteria may need slight downward adjustment in very small infants; consult pediatric radiology
— Higher anesthetic risk — coordinate with neonatology and pediatric anesthesia
— Postoperative apnea risk is heightened; consider postop monitoring in NICU rather than general ward
— Congenital heart disease: ensure cardiology input; carefully balance fluids to avoid overload; avoid hypoxemia during induction in shunt-dependent lesions
— Tracheoesophageal fistula (post-repair): rare coincidence but reported; coordinate airway management
— Trisomy 21 and other syndromes: HPS not classically associated, but vomiting in these infants raises broader differential (duodenal atresia, malrotation)
— Review for macrolides (causative association)
— Review for PPIs/H2 blockers — may mask gastritis-related hematemesis
— Rare in this age group; if present (e.g., congenital nephrotic syndrome, biliary atresia), adjust fluid composition and rates carefully
— Hepatic dysfunction may exacerbate the icteropyloric jaundice picture
— Persistent vomiting after pyloromyotomy → consider incomplete myotomy, GERD, eosinophilic gastroenteritis, milk protein allergy, or missed malrotation
— Repeat ultrasound or UGI as indicated
Key distinction: In a preterm infant at 10 weeks chronologic age with new projectile vomiting, do not dismiss HPS because the age seems "late" — calculate corrected/postmenstrual age and image accordingly.
Board pearl: Postmenstrual age ~6 weeks corrected is the more reliable timing predictor than chronologic age in preterm infants.
— Multifactorial polygenic inheritance with male predominance
— Mother with prior HPS: ~20% recurrence risk in male offspring, ~7% in female
— Father with prior HPS: ~5% in male offspring, ~2.5% in female
— Sibling history: ~3–5% recurrence risk
— No single-gene test clinically useful; NOS1 and other susceptibility loci identified but not actionable
— Educate on early signs: progressive nonbilious vomiting, poor weight gain in weeks 2–8
— Low threshold for clinical evaluation if symptoms develop
— Reassure that early diagnosis and treatment yield excellent outcomes
— Macrolides in late pregnancy or while breastfeeding (especially erythromycin) — counsel mothers to discuss alternatives when feasible
— Avoid neonatal macrolide exposure in the first 2 weeks of life when clinically possible; if pertussis prophylaxis is indicated, weigh risk-benefit and counsel parents
— HPS is more common in formula-fed infants, though breastfed infants are not immune
— Encourage breastfeeding continuation after pyloromyotomy — protective against postoperative infection and supports recovery
— Mother can pump and store milk during preoperative NPO period
— First-born males of European descent at highest baseline risk
— Female infants of mothers with HPS warrant similar vigilance despite lower base rate
— Routine ultrasound screening of asymptomatic siblings is not recommended
— Clinical vigilance and parental education are the preventive strategy
Step 3 management: In a postpartum counseling visit for a mother whose first child had HPS, the actionable advice is early recognition education and avoidance of unnecessary neonatal macrolides, not prophylactic imaging.
Board pearl: Erythromycin in the first 2 weeks of life carries the strongest medication association with HPS — document this exposure in any vomiting infant.
— Severe dehydration and hypovolemic shock
— Hypochloremic hypokalemic metabolic alkalosis with paradoxical aciduria
— Hypoglycemia from depleted glycogen and poor intake
— Failure to thrive, weight below birth weight
— Aspiration pneumonia from recurrent vomiting
— Indirect hyperbilirubinemia (icteropyloric syndrome) — resolves after definitive treatment
— Hematemesis from gastritis/Mallory-Weiss-type tears
— Mucosal perforation (1–3%) — usually at duodenal end; recognized with air or methylene blue insufflation, repaired primarily
— Bleeding from hypertrophied muscle edge — usually minor, controlled with pressure
— Anesthetic complications — postoperative apnea, especially if residual alkalosis
— Persistent vomiting
— Mild and self-limited in 50–80% for first 24–48 hours (mucosal edema)
— If persistent beyond 5–7 days → suspect incomplete myotomy, GERD, or missed alternative diagnosis; obtain UGI or repeat ultrasound
— Wound complications: infection (1–2%), dehiscence, incisional hernia
— Incisional site granuloma (especially umbilical approach)
— Recurrence/incomplete myotomy: rare (<1%); reoperation curative
— Postoperative apnea: highest risk in preterm infants and those with uncorrected alkalosis at induction
— Excellent prognosis — pyloromyotomy is curative
— No association with adult gastric pathology, motility disorders, or cancer
— Normal growth, development, and feeding tolerance expected
— Cosmetic outcome generally good, especially with laparoscopic approach
Key distinction: Expected postoperative vomiting (first 1–2 days, decreasing frequency, infant feeding well between episodes) vs pathologic postoperative vomiting (persistent beyond a week, projectile, weight loss) — the latter warrants imaging.
Board pearl: Postoperative apnea in HPS infants is driven by uncorrected CSF alkalosis that suppresses central respiratory drive — yet another reason to correct labs before operating.
— Pediatric surgery — primary surgical service for pyloromyotomy
— Pediatric anesthesia — preoperative airway and metabolic assessment
— Pediatric radiology — for ultrasound or UGI interpretation
— Pediatric hospitalist or neonatology for medical management on the floor
— Severe dehydration (>10%) with hemodynamic compromise
— Severe metabolic alkalosis (HCO₃⁻ >35) requiring slow controlled correction
— Persistent altered mental status, lethargy, or apneic episodes
— Significant electrolyte derangements requiring frequent (q2h) monitoring
— Postoperative apnea or respiratory complications
— Preterm infants with comorbidities
— Community hospital without pediatric surgical, anesthesia, and PICU capability should stabilize and transfer
— Pre-transfer stabilization: IV access, NS bolus if hypovolemic, NPO, NG decompression if needed, electrolyte assessment
— Communicate severity, labs, and time of last feed to receiving team
— Inadequate urine output despite resuscitation
— Rising lactate or worsening acidosis (suggests alternative diagnosis or sepsis)
— Bilious emesis appearing during workup — reconsider malrotation, obtain emergent UGI
— New abdominal distension, peritoneal signs, or hemodynamic deterioration
— Persistent vomiting >5–7 days
— Fever, wound erythema, or drainage
— Signs of peritonitis (concern for missed mucosal perforation)
CCS pearl: On CCS, advance the clock in 2–4 hour increments during preoperative resuscitation, re-checking labs and vitals; do not jump to operating room until chloride and bicarbonate normalize.
Step 3 management: A community ED with a confirmed HPS infant should stabilize with IV fluids and transfer to a pediatric surgical center — not attempt local operative management.
— Malrotation with midgut volvulus
— Bilious vomiting, often acute onset, any age but classically <1 month
— Surgical emergency — bowel ischemia within hours
— Upper GI series is diagnostic; do not delay for ultrasound
— Key distinction: bilious vomiting in an infant is malrotation until proven otherwise
— Duodenal atresia
— Presents in the first 1–2 days of life with bilious vomiting
— "Double bubble" sign on plain film
— Strong association with Down syndrome (~30%), polyhydramnios
— Jejunal/ileal atresia: bilious vomiting, distension, distal obstruction pattern
— Hirschsprung disease: failure to pass meconium >48h, bilious emesis, distension; rectal biopsy diagnostic
— Incarcerated inguinal hernia: groin mass, irritability, vomiting; exam-based diagnosis
— Intussusception: typically older (6–36 months), "currant jelly" stools, intermittent colicky abdominal pain, target/donut sign on US; rare <3 months
— Antral web, pyloric atresia: rare congenital obstructions; UGI or endoscopy diagnostic
— Necrotizing enterocolitis: preterm predominantly, bloody stools, pneumatosis on KUB
Key distinction table — at-a-glance:
— Nonbilious + projectile + 3–6 weeks + hungry vomiter → HPS
— Bilious + any age + acutely ill → Malrotation/volvulus (UGI now)
— Bilious + day 1 of life + double bubble → Duodenal atresia
— Currant jelly stool + colicky pain + 6–36 mo → Intussusception
— No meconium in 48h + distension → Hirschsprung
Board pearl: Bilious vomiting and pyloric stenosis are mutually exclusive — the obstruction in HPS is proximal to the ampulla of Vater, so bile cannot reflux into the stomach. If the vignette says "green emesis," it is not HPS.
Step 3 management: Any infant with bilious vomiting gets emergent upper GI series and surgical consultation — not an abdominal ultrasound.
— Effortless, non-projectile spit-up, infant is happy and gaining weight ("happy spitter")
— Onset often in first weeks, peaks at 4 months, resolves by 12–18 months
— Management: positioning, smaller more frequent feeds, thickened feeds, parental reassurance
— Pharmacotherapy (H2 blockers, PPIs) reserved for GERD with complications
— Volumes >150–180 mL/kg/day; weight gain normal or excessive
— Resolves with volume adjustment
— Vomiting + blood/mucus in stool, eczema, irritability
— Resolves on extensively hydrolyzed or amino-acid formula
— Fever, diarrhea, sick contacts; anorectic infant (not hungry vomiter)
— Vomiting may be the only symptom in young infants
— Obtain catheterized urine in any vomiting febrile infant
— Lethargy, poor feeding, fever or hypothermia, bulging fontanelle
— Mandates full sepsis workup including LP
— Hydrocephalus, intracranial hemorrhage, mass
— Bulging fontanelle, sunsetting eyes, macrocephaly, sutural diastasis
— Onset often within first weeks; lethargy, hypoglycemia, anion-gap metabolic acidosis (contrast with HPS alkalosis), hyperammonemia
— Examples: urea cycle disorders, organic acidemias, galactosemia
— Hyponatremia, hyperkalemia, metabolic acidosis in a 1–4 week old
— Ambiguous genitalia in females; males may appear normal
— Newborn screen catches most cases
Key distinction: HPS = hypochloremic hypokalemic metabolic alkalosis. CAH = hyponatremia, hyperkalemia, metabolic acidosis. IEM = anion-gap acidosis ± hyperammonemia. The electrolyte signature alone often narrows the differential.
Board pearl: A vomiting febrile infant always needs a urinalysis and urine culture — UTI is the most under-recognized medical mimic.
— Ad libitum feeding with breast milk or standard infant formula is acceptable and non-inferior to structured advancement
— Resume feeds 4–8 hours after surgery
— Expect 1–3 episodes of vomiting in the first 24 hours; this should not prompt re-imaging
— Most infants tolerate full feeds and are discharged within 24–48 hours
— Tolerating goal volume feeds (typically 60–90 mL every 3–4 hours for term infants)
— Adequate urine output and stool production
— Stable weight or weight gain trajectory
— No fever, wound looking clean and dry
— Family comfortable with feeding plan and recognizing red flags
— Acetaminophen as needed for postoperative discomfort
— No routine antibiotics, no acid suppression unless specific indication
— Vitamin D supplementation if exclusively breastfed (routine pediatric recommendation, not HPS-specific)
— Resume normal feeding patterns and routine well-child schedule
— Continue vaccinations on schedule
— Red flags to return: persistent vomiting beyond 1 week, projectile vomiting recurrence, fever, wound redness/drainage, poor feeding, decreased wet diapers
— Curative procedure: no expected long-term GI sequelae
— Normal growth and development expected
— No dietary restrictions, no activity limitations
— Cosmetic outcome typically excellent
— Inform family of recurrence risk in future children (5–20% depending on parental gender)
— Educate on early recognition
Step 3 management: Postoperative HPS infants do not need outpatient PPIs, motility agents, or dietary restrictions — routine pediatric care resumes.
Board pearl: Ad lib feeding after pyloromyotomy shortens length of stay and is current standard of care — structured advancement protocols are outdated.
— Surgical follow-up at 2–4 weeks to assess wound healing and feeding tolerance
— Primary pediatric care visit within 1–2 weeks of discharge to assess weight gain, hydration, parental coping
— Resume routine well-child schedule at 2 months (next scheduled visit) including immunizations
— Weight trajectory — should rapidly catch up to growth curve; expect 20–30 g/day gain
— Feeding volumes and frequency — should normalize within 1–2 weeks
— Wound inspection — clean, dry, healing; umbilical site granulomas occur and resolve with silver nitrate
— Stool and urine output patterns
— Persistent vomiting beyond 1 week post-discharge → UGI series to evaluate for incomplete myotomy or GERD
— Poor weight gain → assess feeding technique, volumes, possible GERD or alternative diagnosis
— Fever or wound concerns → exam, possible imaging for abscess
— Reassure that surgery is curative; no recurrence in the same child
— Address feeding anxiety — common after a stressful illness
— Encourage breastfeeding continuation if applicable; lactation support if needed
— Provide written red-flag list
— Catch-up growth expected; no special formula or supplements needed
— Solid food introduction at usual 4–6 months
— Routine developmental surveillance
— Document HPS history in pediatric record
— At later well-child or postpartum visits, counsel on recurrence risk and early recognition for future children
Step 3 management: Surveillance abdominal ultrasounds are not indicated after successful pyloromyotomy — clinical assessment alone suffices.
Board pearl: The most common cause of persistent post-pyloromyotomy vomiting beyond 5–7 days is GERD or feeding intolerance, not surgical failure — but rule out incomplete myotomy with imaging before attributing to medical causes.
— Obtain from both parents when feasible, or legal guardian
— Discuss: risks of anesthesia, mucosal perforation, bleeding, infection, incomplete myotomy, scar, postoperative apnea
— In emancipated minor or teenage parent scenarios, the minor parent generally retains decisional authority for their child; verify state law
— Surrogate decision-making: if both parents unavailable, follow institutional policy (typically grandparent or guardian; emergent care can proceed without consent if life-threatening)
— Community hospital to tertiary center transfer: communicate labs, last feed, NPO status, IV fluids running, vital signs trend; use standardized handoff (SBAR, I-PASS)
— OR to recovery to ward: handoff must include intraoperative findings (especially any mucosal violation), fluid status, electrolyte targets, postoperative feeding plan
— Inpatient to outpatient discharge: confirm follow-up scheduled, parents demonstrate understanding of red flags (teach-back)
— Operating before electrolyte correction → postoperative apnea, arrhythmia
— Missed bilious vomiting → catastrophic malrotation/volvulus delay
— Failure to recognize mucosal perforation intraoperatively → postoperative peritonitis, sepsis
— Anchoring bias: assuming all infant vomiting is reflux without examining or imaging
— Wrong-site surgery prevention: time-out per universal protocol
— Severe dehydration from delayed presentation does not by itself constitute neglect — HPS is insidious and parents often present appropriately once weight loss is evident
— If history reveals prolonged neglect, refusal of care, or other red flags (bruising, inconsistent history), report to child protective services per state law
— Ensure follow-up appointments are scheduled before discharge
— Address language barriers with certified medical interpreters — not family members — when consenting and providing discharge instructions
— Coordinate with insurance for transport and follow-up coverage
Step 3 management: A non–English-speaking family receiving HPS surgical consent requires a certified medical interpreter — using a family member, especially a minor sibling, is a documented patient safety and ethics violation.
Board pearl: Mucosal perforation discovered postoperatively (peritonitis, fever) is a never-event-adjacent complication — early recognition and reoperation are mandatory.
Key distinction: Pyloric stenosis is acquired muscular hypertrophy peaking at 3–6 weeks, not a congenital obstruction. Pyloric atresia and antral webs are congenital and rare.
Board pearl: If the question stem mentions erythromycin exposure in a neonate, expect HPS to be the answer.
— A 5-week-old first-born boy presents with 1 week of progressive nonbilious projectile vomiting after feeds. He is eager to feed afterward. Mucous membranes are dry. Labs show Na 138, K 3.1, Cl 88, HCO₃ 34. Next best step?
— Answer: IV fluid resuscitation with normal saline and electrolyte correction (not surgery, not ultrasound — the diagnosis is clear, stabilize first; or ultrasound if diagnosis not yet confirmed)
— A 4-week-old infant who completed a course of oral erythromycin at 1 week of life for pertussis prophylaxis now has projectile vomiting. Most likely diagnosis?
— Answer: Hypertrophic pyloric stenosis
— A 3-week-old infant with bilious vomiting and irritability. Next step?
— Answer: Emergent upper GI series and pediatric surgery consult — not abdominal ultrasound. Diagnosis is malrotation/volvulus, not HPS
— A vomiting 5-week-old has Cl 86, HCO₃ 36, K 2.9, urine pH 5.5. Mechanism of urine acidity?
— Answer: Volume depletion → aldosterone → renal Na⁺ reabsorption with H⁺ and K⁺ secretion → paradoxical aciduria despite systemic alkalosis
— Confirmed HPS infant; surgeon wants to operate now. Labs: Cl 88, HCO₃ 33, K 3.0. Best response?
— Answer: Defer surgery until electrolytes are corrected; postoperative apnea risk from persistent alkalosis
— Day 6 post-pyloromyotomy, infant still vomiting all feeds. Next step?
— Answer: Upper GI series to evaluate for incomplete myotomy
— Mother had HPS as an infant; what is the risk to her future son? — ~20%
— Effortless spit-up in a thriving 2-month-old → GERD, not HPS
Step 3 management: Recognize the "next best step" rhythm — image, resuscitate, correct, then operate. Skipping a step is the wrong answer.
Board pearl: When the lab pattern is low Cl, low K, high HCO₃ in a vomiting infant, the diagnosis is HPS until proven otherwise.
Hypertrophic pyloric stenosis is acquired pyloric muscle hypertrophy in a 3–6-week-old first-born male presenting with nonbilious projectile vomiting and hypochloremic hypokalemic metabolic alkalosis, diagnosed by abdominal ultrasound (muscle ≥3 mm, channel ≥15 mm) and definitively treated with Ramstedt pyloromyotomy after fluid and electrolyte resuscitation.
— Nonbilious projectile vomiting in a hungry infant aged 3–6 weeks
— Risk factors: first-born male, European descent, neonatal erythromycin exposure, family history
— Bilious vomiting excludes HPS — pursue malrotation workup instead
— Abdominal ultrasound is first-line: muscle thickness ≥3 mm, channel length ≥15 mm
— CMP shows hypochloremic, hypokalemic metabolic alkalosis with paradoxical aciduria
— Upper GI series (string sign, double-track) is reserved for equivocal cases or when malrotation must be excluded
— Resuscitate before you operate — NPO, IV NS bolus, then D5 ½NS + KCl
— Pre-op targets: Cl⁻ >100, HCO₃⁻ <30, K⁺ normal, urine output established
— Ramstedt pyloromyotomy (laparoscopic preferred) is curative
— Ad lib feeds within 4–8 hours postoperatively; discharge in 24–48 hours
— Lactated Ringer's worsens alkalosis — use normal saline
— Postoperative apnea risk if alkalosis not corrected pre-op
— Mucosal perforation (1–3%) is the key intraoperative complication
— Persistent post-op vomiting beyond a week → UGI to evaluate incomplete myotomy
— Family recurrence risk is meaningful (5–20%) — counsel parents
Board pearl: HPS is a medical resuscitation followed by a surgical cure — knowing the order of operations is the single most testable principle on Step 3.
Step 3 management: Always stabilize, image, correct, operate, then advance feeds ad lib — in that order, every time.