MCCQE Part I pediatrics questions

At 5 minutes: heart rate >100/min = 2, strong cry (respiratory effort) = 2, active motion (tone) = 2, cough/grimace on suctioning = 2, completely pink (colour) = 2, giving a total of 10. The APGAR score assesses heart rate, respiratory effort, muscle tone, reflex irritability, and colour, each scored 0-2, and is used to evaluate the need for resuscitation rather than to predict long-term neurologic outcome.

• A. Incorrect total; does not account for full points in colour and reflex categories.
• B. Incorrect total; underestimates several categories that score 2 at 5 minutes.
• C. Incorrect total; underestimates several categories that score 2 at 5 minutes.
• D. Incorrect total; underestimates several categories that score 2 at 5 minutes.

According to the Neonatal Resuscitation Program algorithm, an infant who remains apneic or has a heart rate below 100/min after initial steps (drying, stimulation, positioning, clearing the airway) requires positive pressure ventilation. Chest compressions are reserved for a heart rate below 60/min despite adequate ventilation for 30 seconds. Epinephrine is used only if the heart rate remains below 60/min despite effective PPV and compressions. Free-flow oxygen alone does not provide the ventilatory support needed for an apneic infant.

• A. Routine tracheal suctioning for meconium is not recommended regardless of fluid character; ventilation takes priority if the infant is apneic.
• B. Chest compressions are indicated only for a heart rate below 60/min despite adequate PPV.
• C. Epinephrine is reserved for persistent bradycardia below 60/min despite effective ventilation and compressions.
• D. Free-flow oxygen does not assist ventilation in an apneic infant and is not the appropriate next step.

Newborn metabolic screening (Guthrie card) is performed between 24 and 72 hours of life to allow sufficient time for metabolite accumulation and protein intake, which improves detection of conditions such as phenylketonuria, congenital hypothyroidism, and other inherited metabolic disorders. Screening too early, such as immediately after birth, risks false negatives because abnormal metabolites may not yet be present in detectable concentrations. This is a population-based screening program in all Canadian provinces, performed regardless of symptoms, since many of these conditions are clinically silent at birth.

• A. Waiting until 2 weeks significantly delays treatment and is outside the recommended screening window.
• B. Screening is universal and performed on all infants regardless of symptoms, since the conditions detected are often asymptomatic at birth.
• C. Waiting until 1 week delays diagnosis and treatment of conditions requiring early intervention, such as congenital hypothyroidism.
• E. Screening immediately after birth risks false-negative results because metabolites have not yet accumulated.

An abnormal newborn screen for congenital hypothyroidism must be confirmed with serum free T4 and TSH levels before starting treatment, as screening tests have false positives and the diagnosis requires biochemical confirmation. Early initiation of levothyroxine, once confirmed, is critical to prevent irreversible intellectual disability, so treatment should begin promptly once confirmatory serum testing supports the diagnosis rather than waiting for symptoms, which are often absent in the neonatal period. Imaging studies may help determine etiology but are not required before starting treatment.

• A. Reassurance without confirmatory testing risks delaying treatment during a critical window for neurodevelopment.
• C. Starting treatment without confirmatory serum testing exposes the infant to unnecessary therapy if the screen was a false positive.
• D. Ultrasound may help identify the cause (e.g., thyroid dysgenesis) but is not the required confirmatory step before treatment.
• E. A radioiodine scan is not first-line, involves radiation exposure in a neonate, and is not needed to confirm the diagnosis.

When the total serum bilirubin plots above the phototherapy threshold on the hour-specific nomogram for a term infant without risk factors, conventional phototherapy should be initiated to reduce bilirubin levels and prevent progression toward levels requiring exchange transfusion. Exchange transfusion is reserved for bilirubin levels approaching or exceeding the exchange transfusion threshold, or for infants with signs of acute bilirubin encephalopathy. Stopping breastfeeding is not recommended as first-line management since it does not clearly hasten resolution and interferes with maternal-infant bonding and lactation establishment.

• A. IVIG is reserved for specific cases of isoimmune hemolytic disease (e.g., Rh or ABO incompatibility) with rapidly rising bilirubin, not routine management at this threshold.
• B. Delaying treatment risks progression to levels associated with bilirubin-induced neurologic dysfunction.
• D. Discontinuing breastfeeding is not recommended as first-line management of hyperbilirubinemia at this level.
• E. Exchange transfusion is reserved for levels at or near the exchange threshold or evidence of encephalopathy, not for levels at the phototherapy threshold.

Breast milk jaundice, seen in Infant B, is thought to result from factors in breast milk, such as beta-glucuronidase and certain fatty acids, that increase intestinal bilirubin reabsorption and inhibit hepatic conjugation, causing a prolonged unconjugated hyperbilirubinemia in an otherwise thriving infant. This differs from breastfeeding jaundice (Infant A), which occurs in the first week of life and results from inadequate milk intake causing weight loss, dehydration, and reduced stooling, which increases enterohepatic recirculation of bilirubin. Breast milk jaundice typically peaks in the second to third week and can persist for weeks to months but does not require cessation of breastfeeding.

• A. Hemolytic disease typically presents within the first days of life with more significant jaundice, not as isolated prolonged jaundice in a thriving 3-week-old.
• C. Delayed meconium passage is relevant to early breastfeeding jaundice from poor intake, not to breast milk jaundice in a well-fed infant at 3 weeks.
• D. Dehydration-related hemoconcentration is a feature of breastfeeding jaundice from poor intake, not the mechanism in a well-fed 3-week-old.
• E. This mechanism describes breastfeeding jaundice (Infant A), due to poor intake, not breast milk jaundice at 3 weeks with good feeding.

Vitamin K is administered intramuscularly shortly after birth to prevent vitamin K deficiency bleeding, also called hemorrhagic disease of the newborn, which results from low vitamin K stores at birth, poor placental transfer, and low levels in breast milk, predisposing to potentially life-threatening bleeding including intracranial hemorrhage. The Canadian Paediatric Society recommends a single intramuscular dose for all newborns, as oral regimens have less reliable absorption and require multiple doses with higher risk of missed administration. If parents refuse, this decision should be documented, and the physician should ensure the family understands the risk of serious, sometimes fatal, bleeding, particularly later-onset intracranial hemorrhage.

• A. Kernicterus relates to bilirubin management, such as phototherapy, not vitamin K.
• C. Vitamin D, not vitamin K, is relevant to prevention of rickets, and is addressed through separate supplementation guidance.
• D. GBS sepsis prophylaxis is addressed through intrapartum antibiotics based on maternal screening, not vitamin K administration.
• E. Necrotizing enterocolitis is primarily a concern in preterm infants and is unrelated to vitamin K status.

Breech presentation is a major risk factor for developmental dysplasia of the hip (DDH), even when the clinical hip examination (Barlow/Ortolani) is normal, because physical examination has imperfect sensitivity, especially in the first days of life. Canadian Paediatric Society guidelines recommend hip ultrasound at 6 weeks of age for infants with major risk factors (breech presentation, family history of DDH, or clinical instability), since ultrasound is the most sensitive imaging modality for immature cartilaginous hips. Radiographs are unreliable before 4-6 months because the femoral head is not yet ossified. Ultrasound at 6 weeks allows accurate assessment of acetabular morphology and femoral head coverage while avoiding false positives from physiologic laxity present in the first weeks of life.

• A. Prophylactic harness treatment without confirmed imaging findings is not indicated and exposes the infant to unnecessary treatment and complications such as avascular necrosis.
• B. Reassurance alone is insufficient because breech presentation confers a significant risk of DDH even with a normal initial examination.
• C. Radiographs are unreliable in early infancy because the femoral head and acetabulum are largely cartilaginous and poorly visualized.
• D. Specialist referral for examination under anesthesia is premature before completing standard screening ultrasound at the appropriate age.

Caput succedaneum is a diffuse edematous swelling of the scalp caused by pressure during delivery, which crosses suture lines because the fluid lies above the periosteum in the subcutaneous tissue. It is present at birth, pits on pressure, and typically resolves within a few days without intervention. In contrast, cephalohematoma is a subperiosteal collection of blood that is limited by suture lines, appears hours after birth, and does not pit. Vacuum-assisted deliveries increase the risk of both conditions, but the key distinguishing features here (present at birth, crosses sutures, pitting) point to caput succedaneum.

• A. Subgaleal hemorrhage is a diffuse, boggy, fluctuant collection that can cross sutures but is typically more extensive, expands over time, and can cause significant blood loss and hypovolemia, which is not described here.
• C. Encephalocele is a midline skull defect with herniation of brain tissue, presenting as a non-pitting mass often with a visible bony defect, not a diffuse pitting scalp swelling after delivery.
• D. Cephalohematoma does not cross suture lines and typically appears gradually after birth rather than being present immediately.
• E. Craniosynostosis presents with an abnormally shaped skull due to premature suture fusion, not a soft pitting scalp swelling.

Sitting without support typically develops by 6-8 months, and pulling to stand while cruising along furniture is expected by 9-10 months, with independent walking typically achieved between 12-15 months. A 10-month-old who sits well and pulls to stand but is not yet crawling or walking independently is within the normal range of motor development. Developmental milestones occur along a spectrum, and absence of independent walking is not expected or concerning until 18 months. No red flags such as asymmetry, loss of previously acquired skills, or significant hypotonia are described.

• A. There is no delay present; the child's milestones are appropriate for age, so physiotherapy referral is unnecessary.
• C. Global developmental delay requires delays across multiple domains and is not supported by this isolated description of normal gross motor skills.
• D. Neurology referral is not indicated for a child demonstrating age-appropriate motor milestones.
• E. There is no description of loss of previously acquired skills, so regression is not present.

By 12 months, children should have at least one or two meaningful words, respond to their name, and use gestures such as pointing. By 18 months, lack of single words, absence of pointing to show interest, and inconsistent response to name are red flags that warrant prompt referral rather than watchful waiting. Hearing loss must be ruled out first with audiologic testing since it is a common and treatable cause of language delay, alongside developmental assessment to evaluate for autism spectrum disorder or global delay. Early identification and intervention improve long-term outcomes, so referral should not be delayed.

• B. Lead screening is not the first-line investigation for isolated language delay in the absence of risk factors for lead exposure.
• C. Simply increasing home language exposure without professional assessment risks missing a treatable or significant underlying condition and delays intervention.
• D. Speech therapy alone without first assessing hearing and broader development could miss an underlying cause such as hearing loss or autism spectrum disorder.
• E. Delaying reassessment for 6 months is inappropriate given clear red flags at 18 months that warrant timely evaluation.

The majority of failure to thrive cases, especially in the context of psychosocial risk factors like food insecurity and recent immigration, are non-organic in etiology and relate to inadequate caloric intake. The weight dropping disproportionately to length, with a well-appearing child and no systemic symptoms, argues against an organic cause. The appropriate initial step is a thorough dietary, feeding, and psychosocial history, including observed feeding, to assess caloric intake, feeding technique, and food security before pursuing invasive or expensive investigations. Organic causes should be considered if red flags emerge, such as vomiting, diarrhea, dysmorphism, or if initial nutritional intervention fails.

• A. Inpatient admission is reserved for severe malnutrition, safety concerns, or failure of outpatient management, not as an initial step.
• C. Endoscopy is invasive and not indicated as an initial step without specific red flags for structural gastrointestinal disease.
• D. Sweat chloride testing is reserved for cases with features suggestive of cystic fibrosis such as respiratory symptoms, steatorrhea, or meconium ileus history, none of which are present.
• E. Celiac disease typically presents with gastrointestinal symptoms or growth failure in both weight and length, and is not the most likely explanation given the psychosocial context and isolated weight faltering.

The features described, lack of eye contact, absence of response to joint attention cues like waving, repetitive play patterns, lack of communicative use of language, and reduced interest in peers, are classic early red flags for autism spectrum disorder. The Canadian Paediatric Society and the Rourke Baby Record recommend using a validated screening tool such as the Modified Checklist for Autism in Toddlers, Revised (M-CHAT-R) when such red flags are identified at routine surveillance visits. Early identification through screening allows for timely referral to developmental pediatrics and early intervention services, which improves long-term outcomes. Genetic testing and EEG may be considered later in the diagnostic workup but are not the appropriate initial step.

• A. These are recognized red flags for autism spectrum disorder, not normal variants, and delaying assessment could postpone early intervention.
• B. There is no description of seizure activity such as staring spells or convulsions, so EEG is not indicated as an initial step.
• D. Genetic testing for fragile X syndrome may be part of a later etiological workup after autism is suspected or confirmed, but it is not the first step in evaluating these behavioral red flags.
• E. Simply increasing social opportunities without formal screening risks missing or delaying diagnosis of a condition that benefits from early intervention.

In school-age children with confirmed ADHD, Canadian guidelines recommend behavioral interventions and environmental or classroom accommodations as the foundation of initial management, particularly for mild to moderate impairment, with pharmacotherapy added if behavioral measures alone do not adequately control symptoms. Diagnosis requires symptoms of inattention and/or hyperactivity-impulsivity present in two or more settings (home and school) for at least 6 months, causing functional impairment, as described in this case. Stimulant medications such as methylphenidate are effective and often necessary for moderate to severe ADHD, but behavioral strategies and parent/teacher training are recommended as the first-line approach, often used concurrently with medication when started. Dietary elimination has not been shown to have consistent benefit and is not recommended as primary therapy.

• A. Dietary elimination of food colorings and sugar lacks consistent evidence for efficacy in ADHD and is not recommended as a first-line management strategy.
• C. Inpatient admission is not indicated for straightforward ADHD without safety concerns or comorbid acute psychiatric crisis.
• D. Stimulant medication is not required as the sole or immediate first step; behavioral strategies and accommodations are recommended as the initial approach, particularly before escalating directly to medication without trial of behavioral measures.
• E. Atomoxetine is a second-line pharmacologic option, not monotherapy as the very first intervention before behavioral measures are tried.

Persistent hypoxemia (oxygen saturation below 94%), tachypnea, and moderate retractions despite an adequate trial of bronchodilators and systemic corticosteroids indicate an incomplete response to initial emergency treatment, which is an accepted criterion for hospital admission. Discharge would be unsafe given ongoing hypoxemia and respiratory distress. Intramuscular epinephrine is reserved for anaphylaxis, not status asthmaticus. Adding a long-acting beta-agonist is inappropriate for an acute exacerbation and is not indicated as monotherapy or for acute rescue in children.

• A. Intramuscular epinephrine is used for anaphylaxis, not for an asthma exacerbation.
• C. Routine follow-up is inappropriate given ongoing hypoxemia and increased work of breathing.
• D. Long-acting beta-agonists are not used for acute exacerbations and this child requires admission, not discharge.
• E. Discharge is unsafe because she still has hypoxemia and moderate respiratory distress after treatment.

A witnessed choking episode during eating, unilateral decreased breath sounds and wheeze, and unilateral hyperinflation with mediastinal shift away from the affected side on expiration are classic for foreign body aspiration causing partial ball-valve obstruction of the right main bronchus. Bronchoscopy is required for both diagnosis and removal. Pneumonia typically presents with fever and consolidation rather than unilateral hyperinflation. Bronchiolitis causes bilateral, not unilateral, findings and occurs typically in infants under 2 years with a viral prodrome. Pneumothorax would show absent lung markings and mediastinal shift away from the affected side, not hyperinflation of the affected lung, and spontaneous pneumothorax is rare in toddlers.

• A. Pneumonia would typically present with fever and radiographic consolidation rather than isolated unilateral hyperinflation after a choking episode.
• C. There is no history of allergic reaction, and the unilateral findings following witnessed choking point to airway obstruction, not bronchospasm.
• D. Bronchiolitis causes bilateral wheeze in infants with a viral prodrome, not unilateral findings following a choking episode.
• E. Pneumothorax shows absent lung markings on the affected side, not hyperinflation, and is uncommon in this age group without trauma.

This infant's presentation with meconium ileus at birth, failure to thrive, and greasy foul-smelling stools (steatorrhea) is classic for cystic fibrosis, and the sweat chloride test remains the gold-standard confirmatory test, with a chloride concentration of 60 mmol/L or greater on two occasions being diagnostic. Fecal elastase can support a diagnosis of pancreatic insufficiency but does not confirm cystic fibrosis specifically. Immunoreactive trypsinogen is used for newborn screening, not diagnostic confirmation, and can have false positives and negatives. Testing for only the single most common CFTR mutation would miss many of the more than 2,000 known disease-causing variants and is not used alone for diagnosis.

• B. Testing a single mutation would miss the majority of CFTR variants and is insufficient to confirm or exclude the diagnosis alone.
• C. Immunoreactive trypsinogen is a newborn screening test, not a confirmatory diagnostic test.
• D. Abdominal ultrasound may show findings consistent with meconium ileus but does not confirm the underlying diagnosis.
• E. Fecal elastase indicates pancreatic insufficiency but is not specific or diagnostic for cystic fibrosis.

Pertussis is a nationally notifiable disease in Canada, and confirmed or clinically suspected cases must be reported to the local public health unit to enable contact tracing, post-exposure prophylaxis for close contacts, and surveillance, regardless of hospitalization status. Reporting is mandatory for every confirmed case, not contingent on severity, complications, or the occurrence of additional cases. Reporting obligations are directed to public health authorities, not professional licensing bodies, which are unrelated to communicable disease control.

• A. Reporting is required for every confirmed case regardless of whether hospitalization occurs.
• C. Licensing colleges are not responsible for communicable disease surveillance; reporting goes to public health authorities.
• D. Reporting must occur at the time of diagnosis, not only if complications develop, to allow timely public health intervention.
• E. A single confirmed case must be reported; waiting for a second case would delay essential contact tracing and prophylaxis.

Infants younger than 28 to 90 days with fever (temperature 38.0°C or higher) are at increased risk of serious bacterial infection because clinical appearance is unreliable at this age, even in a well-appearing infant. Standard practice is a full septic workup, including blood culture, urinalysis and urine culture, and lumbar puncture for cerebrospinal fluid analysis and culture, with admission and empiric parenteral antibiotics pending results. Outpatient management or observation alone is not considered safe at this young age given the risk of missing serious bacterial infection such as meningitis or bacteremia. Oral antibiotics would be inadequate empiric coverage and would compromise the ability to obtain accurate cultures.

• A. Oral antibiotics provide inadequate empiric coverage and risk masking culture results without first obtaining cerebrospinal fluid and blood cultures.
• B. Brief observation alone does not reliably exclude serious bacterial infection in an infant this young and is not an accepted alternative to full workup.
• D. Urinalysis alone is insufficient; a full septic workup including blood culture and lumbar puncture is required at this age.
• E. Discharge without further workup is unsafe in this age group even if the infant appears well, due to the risk of occult serious bacterial infection.

A simple febrile seizure is defined as a generalized seizure lasting less than 15 minutes, occurring only once in a 24-hour period, in a child aged 6 months to 5 years without an underlying central nervous system abnormality, with full return to baseline afterward; this episode meets all of these criteria. Children with simple febrile seizures have a long-term risk of epilepsy only slightly above the general population risk and do not require neuroimaging, electroencephalography, or prophylactic anticonvulsant therapy. The degree of fever does not determine whether a seizure is simple or complex; this classification depends on duration, focality, recurrence within 24 hours, and the child's neurologic baseline.

• B. The long-term risk of epilepsy after a simple febrile seizure is only slightly elevated above baseline, not high.
• C. The height of the fever does not classify a seizure as complex; duration, recurrence, and focality are the relevant criteria, and this seizure was simple.
• D. This seizure meets criteria for simple, not complex, febrile seizure, so urgent neuroimaging and electroencephalography are not indicated.
• E. Prophylactic anticonvulsant therapy is not recommended for simple febrile seizures given their benign long-term course.

In neonates, empiric therapy for bacterial meningitis must cover group B Streptococcus, Escherichia coli, Listeria monocytogenes, and other gram-negative organisms, and the standard regimen is ampicillin, which provides Listeria coverage, combined with cefotaxime, which provides broad gram-negative and central nervous system coverage without the kernicterus risk associated with ceftriaxone in neonates. Ceftriaxone is avoided in neonates, particularly in the first weeks of life, because it can displace bilirubin from albumin and precipitate with calcium-containing intravenous solutions. Vancomycin is added in older infants and children to cover resistant Streptococcus pneumoniae but is not part of standard first-line neonatal empiric therapy, and gentamicin does not reliably achieve adequate cerebrospinal fluid concentrations for meningitis treatment.

• B. Ceftriaxone alone does not cover Listeria monocytogenes, which is an important pathogen in this age group, and is avoided in neonates for safety reasons.
• C. Ceftriaxone is avoided in neonates due to the risk of bilirubin displacement and precipitation with calcium-containing solutions.
• D. This combination does not provide adequate gram-negative or Listeria coverage and metronidazole has no role in empiric bacterial meningitis treatment.
• E. Gentamicin has poor cerebrospinal fluid penetration and is not adequate as a sole second agent for treating neonatal meningitis.

Coronary artery aneurysm is the most important complication of Kawasaki disease and can develop even after clinical improvement, so echocardiography is required to assess coronary artery status regardless of symptoms. Current guidelines recommend echocardiograms at diagnosis, at 1 to 2 weeks, and again at 4 to 6 weeks after onset of illness to detect aneurysms, which typically develop in the subacute phase. Echocardiography is non-invasive, safe, and sensitive for detecting coronary artery dilation and aneurysm in children. Angiography is invasive and reserved for cases with large aneurysms or when more detailed anatomic information is needed.

• A. Angiography is invasive and not first-line; it is reserved for complex cases identified on echocardiogram.
• B. Chest radiograph does not adequately visualize the coronary arteries and is not useful for detecting aneurysms.
• C. An ECG alone cannot detect coronary artery dilation or aneurysm and is insufficient surveillance.
• D. Exercise stress testing is not appropriate for an asymptomatic young child and does not replace structural imaging of the coronary arteries.

This child has a high Centor score (fever, tonsillar exudate, tender anterior cervical adenopathy, absence of cough), making group A Streptococcus likely, but confirmation with a rapid antigen detection test or throat culture is recommended before starting antibiotics to avoid unnecessary treatment and to guide appropriate therapy. Confirming streptococcal infection and treating with antibiotics shortens the symptomatic period and reduces transmission, and is the key strategy for preventing acute rheumatic fever. Antistreptolysin O titers reflect past infection and are used in suspected rheumatic fever or post-streptococcal glomerulonephritis, not for diagnosing acute pharyngitis. Clinical criteria alone are not specific enough to reliably distinguish streptococcal from viral pharyngitis.

• A. Empiric antibiotics without confirmatory testing risk overtreatment, since clinical criteria alone cannot reliably distinguish streptococcal from viral pharyngitis.
• B. Antistreptolysin O titers reflect past, not current, streptococcal infection and are not used to diagnose acute pharyngitis.
• C. The absence of posterior cervical lymphadenopathy, splenomegaly, or significant fatigue makes mononucleosis less likely, and this test does not address the question of streptococcal infection.
• E. A complete blood count does not reliably differentiate bacterial from viral pharyngitis and is not the recommended diagnostic step.

Hand-foot-and-mouth disease, caused primarily by coxsackievirus A16 or enterovirus 71, presents with a characteristic distribution of vesicles on the palms, soles, and buttocks along with oral ulcers, typically with low-grade fever and in outbreak settings such as daycares. Varicella instead begins centrally on the trunk and scalp with lesions in various stages of crusting, spreading centrifugally, and is far less likely to spare the trunk. Herpangina involves oral vesicles and ulcers typically on the soft palate and tonsillar pillars without the hand and foot involvement. The combination of distinctive acral distribution plus oral lesions and a known outbreak setting makes hand-foot-and-mouth disease the most likely diagnosis.

• A. Herpetic gingivostomatitis causes painful gingival and oral vesicles with high fever but does not typically produce this acral vesicular distribution.
• C. Impetigo presents with honey-colored crusted lesions from bacterial infection, not vesicles with this distribution and associated oral ulcers.
• D. Varicella classically starts on the trunk and scalp with lesions in different stages (macules, vesicles, crusts) rather than sparing the trunk and concentrating on palms and soles.
• E. Herpangina causes posterior oropharyngeal vesicles and ulcers without the hand, foot, and buttock involvement seen in this child.

Scarlet fever is caused by group A Streptococcus strains producing erythrogenic exotoxin, presenting with the classic sandpaper rash with flexural accentuation, strawberry tongue, and pharyngitis. Penicillin V remains the first-line treatment for confirmed group A streptococcal infection because the organism remains universally susceptible and penicillin has a narrow spectrum and excellent safety profile. A full 10-day course is required to eradicate the organism from the pharynx and prevent complications such as acute rheumatic fever and post-streptococcal glomerulonephritis. Amoxicillin is an acceptable alternative in young children due to more palatable liquid formulations, but doxycycline, antivirals, topical antibiotics, and steroids have no role in treating this bacterial infection.

• B. Acyclovir is an antiviral and has no role in treating this bacterial toxin-mediated illness.
• C. Topical antibiotics do not treat systemic streptococcal infection or eradicate pharyngeal carriage.
• D. Doxycycline is not first-line for group A streptococcal pharyngitis and is generally avoided in young children due to effects on developing teeth.
• E. Corticosteroids do not treat the underlying bacterial infection and are not indicated for scarlet fever.

In infants and young children who are not toilet trained, bladder catheterization is the preferred method for obtaining a urine specimen for culture when a reliable diagnosis is needed, because it provides a sample with minimal risk of contamination from perineal or fecal flora. Bag specimens have unacceptably high contamination and false-positive rates and should not be used to confirm a urinary tract infection diagnosis, only to screen when the pretest probability is low. Suprapubic aspiration is more invasive and typically reserved for situations where catheterization is unsuccessful or contraindicated, such as in boys with phimosis. Clean-catch collection requires voluntary control of voiding and is not feasible in an infant.

• A. Clean-catch collection requires the child to be toilet trained and able to void on command, which is not possible in a 4-month-old.
• B. A cotton ball in the diaper provides a highly contaminated specimen and is not acceptable for diagnosing urinary tract infection.
• C. Bag specimens have high false-positive rates due to contamination and are not adequate for confirming the diagnosis in a febrile infant requiring antibiotics.
• E. Suprapubic aspiration is more invasive than catheterization and is reserved as a second-line option, not a routine first choice.

Hypertrophic pyloric stenosis classically presents in the second to sixth week of life with progressive, non-bilious, projectile vomiting after feeds, a hungry infant despite vomiting, weight loss, and a palpable olive-shaped mass in the right upper quadrant or epigastrium. The vomiting causes loss of hydrochloric acid and volume depletion, producing the characteristic hypochloremic, hypokalemic metabolic alkalosis. Diagnosis is confirmed with abdominal ultrasound showing pyloric muscle thickness greater than 3 mm and channel length greater than 15 to 17 mm. Management is initial fluid and electrolyte correction followed by pyloromyotomy.

• A. GERD does not cause a palpable abdominal mass or hypochloremic alkalosis.
• B. Duodenal atresia presents in the first days of life with bilious vomiting and a classic 'double bubble' sign, not a palpable olive mass at 5 weeks.
• D. Volvulus presents with bilious vomiting and is a surgical emergency, not this gradual non-bilious pattern with alkalosis.
• E. Congenital adrenal hyperplasia (salt-wasting) causes hyperkalemia and hyponatremia with metabolic acidosis, the opposite electrolyte pattern.

Intussusception typically affects children between 6 months and 3 years and presents with intermittent colicky abdominal pain, drawing up of the legs, lethargy between episodes, vomiting, and classically red currant jelly stool with a palpable sausage-shaped mass. Abdominal ultrasound is the investigation of choice, showing the characteristic target sign or doughnut sign on transverse view, and is highly sensitive and specific without radiation exposure. If ultrasound confirms the diagnosis and there are no signs of perforation or peritonitis, an air or contrast enema is both diagnostic and therapeutic, reducing the intussusception in most cases. Surgery is reserved for failed reduction, perforation, or peritonitis.

• A. Colonoscopy is invasive, requires bowel preparation, and is not used in the acute diagnosis of intussusception.
• B. CT exposes the child to unnecessary radiation and is not first-line when ultrasound is readily available.
• C. Plain radiographs may show nonspecific findings or free air if perforated but lack the sensitivity of ultrasound for diagnosis.
• D. An upper GI series is used for suspected malrotation, not intussusception.

Bilious vomiting in a neonate with signs of hemodynamic instability, abdominal distension, and tenderness suggests malrotation with midgut volvulus, a true surgical emergency because of the risk of bowel ischemia and necrosis from twisting of the mesentery around the superior mesenteric artery. When there are signs of peritonitis or shock, immediate surgical consultation and operative exploration take priority over further imaging, since delay risks loss of the entire midgut. In a stable infant with bilious vomiting alone, an upper GI contrast series showing malposition of the duodenojejunal junction would be the investigation of choice, but clinical instability mandates urgent surgery first. Resuscitation with fluids occurs simultaneously while arranging emergent surgery.

• B. Ultrasound can suggest volvulus but should not delay surgical intervention in an unstable infant with peritoneal signs.
• C. Prokinetic agents have no role in this surgical emergency and would dangerously delay definitive treatment.
• D. Observation is dangerous and risks bowel necrosis and infant death from ongoing volvulus.
• E. Imaging is appropriate in a stable infant, but this infant has peritonitis and shock, requiring emergency surgery without delay.

Hirschsprung disease results from failure of neural crest cell migration, leading to an aganglionic segment of distal bowel that fails to relax, causing functional obstruction. Delayed passage of meconium beyond 48 hours, progressive abdominal distension, and explosive stool release on rectal examination (squirt sign) are classic findings, supported by a transition zone on contrast enema. The definitive diagnostic test is a rectal suction biopsy demonstrating absence of ganglion cells and the presence of hypertrophied nerve fibers on histology with acetylcholinesterase staining. This distinguishes Hirschsprung disease from functional constipation, which typically presents later with normal meconium passage and a rectum full of stool on examination.

• A. Stool studies are used to evaluate for infectious enterocolitis, not to confirm Hirschsprung disease.
• C. Repeating contrast imaging does not provide histologic confirmation needed for diagnosis.
• D. Anorectal manometry showing absence of the rectoanal inhibitory reflex is suggestive but not definitive; biopsy remains the gold standard.
• E. Sweat chloride testing is used to diagnose cystic fibrosis, which can cause meconium ileus, not Hirschsprung disease.

Uncomplicated gastroesophageal reflux in infancy is extremely common, affecting up to half of healthy infants, and is a normal physiologic process related to immature lower esophageal sphincter tone rather than disease. This infant has no warning signs such as poor weight gain, feeding refusal, hematemesis, respiratory symptoms, or excessive irritability, so the appropriate management is reassurance, education that symptoms typically resolve by 12 months of age, and simple measures such as upright positioning after feeds. Investigation or pharmacologic treatment is reserved for infants with GERD, meaning reflux associated with troublesome symptoms or complications such as esophagitis, failure to thrive, or respiratory disease.

• A. Routine thickening of feeds is not recommended for simple regurgitation without growth or feeding concerns.
• B. Endoscopy is invasive and reserved for infants with suspected complications, not a well, thriving infant.
• C. Formula changes are considered when cow's milk protein allergy is suspected, not for simple physiologic regurgitation in a thriving breastfed infant.
• E. PPIs are not indicated for uncomplicated regurgitation without warning signs and have been associated with increased infection risk in infants.

Celiac disease is an immune-mediated enteropathy triggered by gluten in genetically susceptible individuals, presenting in children with chronic diarrhea, abdominal distension, failure to thrive, and iron deficiency anemia. With a normal total serum IgA level, the IgA anti-tissue transglutaminase antibody (anti-tTG) test is the recommended initial serologic screening test because of its high sensitivity and specificity. If IgA is deficient, an IgG-based test such as IgG anti-tTG or deamidated gliadin peptide antibody should be used instead. A positive serologic test is followed by duodenal biopsy showing villous atrophy to confirm the diagnosis before starting a gluten-free diet.

• A. IgG anti-tTG is used as an alternative when the patient has IgA deficiency, not as the first-line test when total IgA is normal.
• B. ANA is used in the evaluation of autoimmune conditions such as systemic lupus erythematosus, not celiac disease.
• D. Anti-mitochondrial antibody is associated with primary biliary cholangitis, not celiac disease.
• E. ASCA is associated with Crohn disease, not celiac disease.

This child has clinical signs consistent with mild to moderate dehydration from acute gastroenteritis, including dry mucous membranes, decreased tears, and mild skin tenting, but remains alert with normal capillary refill. For children with mild to moderate dehydration who are able to tolerate oral intake, oral rehydration therapy with a glucose-electrolyte solution given in small, frequent amounts is the first-line treatment recommended by the Canadian Paediatric Society and is as effective as intravenous fluids with fewer complications and shorter emergency department stays. Intravenous fluids are reserved for children with severe dehydration, shock, intractable vomiting, or failure of oral rehydration. Routine antiemetics and nasogastric rehydration are not first-line in this setting.

• A. Antiemetics are not routinely recommended and resuming a regular diet does not address ongoing fluid losses.
• B. IV fluids are reserved for severe dehydration, shock, or failed oral rehydration, not as first-line therapy in this alert child tolerating oral intake.
• C. Nasogastric rehydration is reserved for children who fail oral rehydration attempts, not as an initial approach.
• E. Hospital admission is unnecessary for mild to moderate dehydration that can be managed with oral rehydration therapy.

Slipped capital femoral epiphysis (SCFE) typically occurs in obese adolescents, more commonly boys, during the pubertal growth spurt, presenting with hip, groin, thigh, or knee pain and a limp, sometimes without a clear traumatic event. The hallmark examination finding is obligatory external rotation of the hip with passive flexion, along with limited internal rotation, due to posterior and inferior displacement of the femoral epiphysis relative to the femoral neck. Diagnosis is confirmed with anteroposterior and frog-leg lateral radiographs of the pelvis showing displacement of the epiphysis, and management requires surgical pinning to prevent further slippage; weight-bearing should be restricted and the contralateral hip monitored given the risk of bilateral involvement.

• A. Transient synovitis typically follows a viral illness in younger children (3 to 8 years) and does not cause the obligate external rotation sign.
• B. Developmental dysplasia of the hip presents in infancy, not with new-onset pain in a 12-year-old.
• D. Legg-Calvé-Perthes disease, avascular necrosis of the femoral head, typically affects younger children aged 4 to 8 years, not obese adolescents.
• E. Septic arthritis presents with fever, systemic illness, and an inability to bear weight, which are absent in this afebrile patient.

This child has a subacute, afebrile presentation with normal inflammatory markers but radiographic changes of femoral head sclerosis, flattening, and widening of the joint space, which are classic early findings of avascular necrosis of the femoral head. These imaging findings distinguish the diagnosis from transient synovitis, which has a normal radiograph and resolves within days to weeks. The condition typically affects boys aged 4-8 years and is idiopathic in most cases. Management involves orthopedic referral for containment strategies and monitoring of femoral head shape to prevent long-term deformity.

• A. Juvenile idiopathic arthritis typically involves a persistent effusion with elevated inflammatory markers and often multiple joints, not an isolated radiographic femoral head change.
• B. Transient synovitis causes an effusion and limp but radiographs are normal, not showing epiphyseal flattening or sclerosis.
• D. Slipped capital femoral epiphysis occurs in older, often obese adolescents and shows epiphyseal displacement on radiograph, not flattening and sclerosis of the femoral head itself.
• E. Septic arthritis presents acutely with fever, elevated inflammatory markers, and an unwilling-to-bear-weight child, none of which are present here.

This child meets several Kocher criteria for septic arthritis of the hip: fever greater than 38.5°C, inability to bear weight, elevated ESR, and elevated CRP, placing her at high probability of septic arthritis given the confirmed effusion. Septic arthritis of the hip is an orthopedic emergency because the femoral head is at risk of avascular necrosis and cartilage destruction from bacterial proteases and elevated intra-articular pressure. Urgent joint aspiration both confirms the diagnosis through synovial fluid analysis and culture, and provides therapeutic decompression, and should not be delayed for further imaging. Empiric intravenous antibiotics are started after aspiration, with surgical washout performed if purulent fluid is obtained.

• A. NSAIDs and observation would delay necessary intervention in a condition that can rapidly destroy the joint.
• B. MRI is not required to confirm the diagnosis and would delay definitive treatment; aspiration is both diagnostic and emergent.
• C. A bone scan is not indicated acutely and would delay urgent treatment; it has no role in guiding immediate management of septic arthritis.
• D. Oral antibiotics are inadequate and unsafe given the need for urgent source control and risk of joint destruction.

Excessive cow's milk intake in toddlers causes iron deficiency anemia through several mechanisms: cow's milk is low in iron, it displaces intake of iron-rich solid foods, and it can cause occult intestinal blood loss in some infants through a milk protein-mediated enteropathy. This combination is a well-recognized cause of microcytic anemia with low ferritin in toddlers consuming large volumes of milk, typically more than 700 mL per day. Management involves limiting milk intake to around 500 mL per day, introducing iron-rich foods, and oral iron supplementation. B12 and folate deficiencies cause macrocytic, not microcytic, anemia, which is inconsistent with this child's low MCV.

• A. Lead toxicity can cause microcytic anemia but is not a typical consequence of cow's milk itself and ferritin would not be characteristically low from lead alone.
• B. B12 deficiency produces macrocytic anemia, not the microcytic picture seen here, and cow's milk is actually a source of B12.
• C. Hemolytic anemia from milk protein antibodies is not a recognized mechanism and would show normocytic indices with evidence of hemolysis, not microcytosis and low ferritin.
• E. Folate deficiency causes macrocytic anemia, inconsistent with this child's low MCV and ferritin findings.

The combination of pallor, bruising, bone pain, lymphadenopathy, splenomegaly, and pancytopenia (anemia, leukopenia, and thrombocytopenia together) in a young child is classic for acute lymphoblastic leukemia, the most common pediatric malignancy. Bone pain results from leukemic infiltration of the marrow and periosteum, and cytopenias reflect marrow replacement by blast cells. The diagnosis is confirmed by peripheral blood smear showing blasts and bone marrow aspirate with more than 25% lymphoblasts. Prompt referral to pediatric oncology is essential for staging and initiation of chemotherapy, as ALL has excellent cure rates with modern treatment protocols.

• A. Aplastic anemia causes pancytopenia but typically without lymphadenopathy or splenomegaly, since it reflects marrow failure rather than infiltration.
• B. Infectious mononucleosis causes lymphadenopathy and splenomegaly but does not typically cause pancytopenia or significant bone pain.
• C. Immune thrombocytopenic purpura causes isolated thrombocytopenia with bruising but would not explain the anemia, leukopenia, bone pain, or organomegaly seen here.
• E. Juvenile idiopathic arthritis can cause fatigue and pain but does not typically cause pancytopenia or splenomegaly of this degree.

Wilms tumor (nephroblastoma) classically presents as a smooth, firm, unilateral abdominal mass that typically remains confined to one flank and does not cross the midline, consistent with its origin in the kidney. In contrast, neuroblastoma, which arises from sympathetic ganglia or the adrenal medulla, often presents as an irregular, nodular mass that crosses the midline, encases vessels, and may be associated with elevated urinary catecholamine metabolites (vanillylmandelic acid and homovanillic acid), periorbital ecchymoses from orbital metastases, and systemic symptoms. Wilms tumor is less likely to cross the midline due to its renal capsule containment. Differentiating these two most common pediatric abdominal malignancies relies on mass characteristics, laterality, and associated biochemical and clinical findings.

• B. Periorbital ecchymoses suggest metastatic neuroblastoma, not Wilms tumor.
• C. Elevated catecholamine metabolites are a biochemical marker of neuroblastoma, not Wilms tumor.
• D. An irregular, vessel-encasing mass is typical of neuroblastoma's infiltrative growth pattern, not the more contained growth of Wilms tumor.
• E. Crossing the midline is more characteristic of neuroblastoma, not Wilms tumor.

Infants with Down syndrome have a significantly increased incidence of congenital heart defects, most commonly atrioventricular septal defects, ventricular septal defects, and patent ductus arteriosus, occurring in approximately 40-50% of affected infants. Canadian Pediatric Society guidelines recommend that all infants with Down syndrome undergo echocardiography in the newborn period, regardless of clinical examination findings, because many significant defects are not detectable by auscultation alone and early detection allows timely surgical referral. This is considered a priority investigation given the morbidity and mortality associated with undiagnosed structural heart disease in this population. Other associated conditions, such as duodenal atresia, hypothyroidism, and hearing or vision problems, are also screened for but the cardiac evaluation is the most critical immediate investigation.

• A. Limb anomalies are not a characteristic feature of Down syndrome and a skeletal survey is not a standard immediate newborn investigation.
• C. Seizure disorders are not a primary immediate newborn concern in Down syndrome, and routine EEG screening is not recommended.
• D. Wilms tumor is not characteristically associated with Down syndrome; it is associated with conditions such as Beckwith-Wiedemann syndrome and WAGR syndrome.
• E. Polycystic kidney disease is not a recognized association of Down syndrome.

Fragile X syndrome, caused by a CGG trinucleotide repeat expansion in the FMR1 gene, is the most common inherited cause of intellectual disability. Classic features include a long narrow face, prominent ears, macroorchidism (post-pubertal), autistic-like behaviours including poor eye contact, and speech delay. The X-linked inheritance pattern explains the affected maternal uncle, since males are more severely affected than carrier females. Diagnosis is confirmed with FMR1 CGG repeat analysis.

• A. Down syndrome presents with hypotonia, upslanting palpebral fissures and a single palmar crease, not macroorchidism or a long narrow face.
• B. Prader-Willi syndrome presents with neonatal hypotonia, hyperphagia and obesity, with hypogonadism rather than macroorchidism.
• C. 22q11.2 deletion syndrome causes cardiac defects, hypocalcemia and immune deficiency, not the facial and genital findings described.
• D. Williams syndrome causes elfin facies, cardiovascular anomalies (supravalvular aortic stenosis) and an overly friendly personality, not macroorchidism.

Physicians in every Canadian province and territory have a legal duty to report suspected child abuse or neglect to child protective services, and this duty overrides the need for parental consent or confidentiality. A spiral fracture inconsistent with the stated mechanism, combined with a patterned bruise, raises strong suspicion for non-accidental injury. The report should be made promptly based on reasonable suspicion, not certainty, and does not require the physician to complete all investigations first. Failure to report is itself a legal and professional offence.

• A. Referral alone without reporting fails to meet the mandatory legal obligation and leaves the child unprotected.
• B. Discharging the child home without reporting leaves her at risk of further harm and fails the legal duty to report.
• D. Consent from a suspected abuser is not required and would compromise the child's safety and the integrity of the investigation.
• E. The duty to report is based on reasonable suspicion and must not be delayed pending further investigations.

The classic triad of abusive head trauma (shaken baby syndrome) is subdural hematoma, retinal hemorrhages, and encephalopathy, resulting from acceleration-deceleration and rotational forces during violent shaking. Multilayered, peripheral retinal hemorrhages are highly specific for abusive trauma and are rarely seen in accidental injury or birth trauma. The absence of an adequate trauma history in a non-mobile infant with these findings is a major red flag. This diagnosis requires urgent reporting to child protective services in addition to medical management.

• A. Hemophilia A would not characteristically cause multilayered peripheral retinal hemorrhages, which are a hallmark of abusive trauma.
• C. Bacterial meningitis can cause encephalopathy but does not typically produce subdural hemorrhage or multilayered retinal hemorrhages.
• D. Vitamin K deficiency bleeding typically occurs in the neonatal period in infants who did not receive prophylaxis, not at 3 months with this hemorrhage pattern.
• E. Accidental short falls rarely cause subdural hemorrhage with extensive multilayered retinal hemorrhages, and no fall history was even given.

Under the mature minor doctrine, recognized in Canadian common law and legislation such as Ontario's Health Care Consent Act, a minor who demonstrates sufficient understanding and appreciation of the nature and consequences of a proposed treatment can provide valid informed consent, regardless of age. The physician's role is to assess capacity, not to apply an arbitrary age cutoff or require parental involvement. Confidentiality should be maintained as it would be for an adult patient with capacity, which supports honest healthcare-seeking behaviour in adolescents. There is no legal requirement to involve parents or report consensual sexual activity between adolescents of similar age.

• A. Consensual sexual activity between adolescents is not itself a child protection concern requiring a report.
• C. Notifying parents without her consent breaches confidentiality owed to a capable minor and is not required by law.
• D. Requiring parental consent for a capable mature minor is not legally required and may deter her from seeking necessary care.
• E. A second opinion is not a legal or ethical requirement when a physician has properly assessed capacity in a mature minor.

Precocious puberty in girls is defined as the onset of secondary sexual characteristics before age 8 years. Breast development (thelarche) before this threshold, especially accompanied by growth acceleration and advanced bone age, indicates true precocious puberty and requires investigation for central (gonadotropin-dependent) versus peripheral causes, including LH, FSH, estradiol levels and brain MRI. Pubic hair development alongside breast development further supports a pubertal process rather than an isolated benign variant. Early diagnosis is important because untreated precocious puberty can lead to compromised final adult height due to premature epiphyseal closure.

• A. Constitutional delay refers to delayed, not precocious, puberty and growth, which is the opposite of this presentation.
• B. Premature adrenarche refers to isolated pubic or axillary hair development without breast development or growth acceleration, which does not match this presentation.
• C. Breast development at age 7 years is before the accepted threshold of 8 years and is not considered normal timing.
• D. An isolated ovarian cyst would not typically be accompanied by growth acceleration, advanced bone age and progressive pubic hair development.

The HEEADSSS psychosocial interview (Home, Education/Employment, Eating, Activities, Drugs, Sexuality, Suicide/depression, Safety) should be conducted with the adolescent alone, after explicitly establishing confidentiality with clearly stated limits, such as disclosure if there is risk of harm to self or others. Adolescents are far more likely to disclose sensitive information about substance use, sexual activity, or mental health concerns when parents are not present. Routine well visits are an important and appropriate opportunity for this screening even in the absence of acute complaints, consistent with Canadian Paediatric Society recommendations for comprehensive adolescent care. Establishing this private, confidential interaction also builds trust and models appropriate patient-physician communication as the adolescent transitions toward independent healthcare decision-making.

• A. The physician, not the adolescent, should proactively arrange private time, as many adolescents will not ask for privacy on their own.
• C. A mailed questionnaire completed with parents present removes confidentiality and the opportunity for real-time clinical assessment and follow-up.
• D. Preventive psychosocial screening is a core component of adolescent well-care visits and should not be deferred simply because there is no acute complaint.
• E. Conducting sensitive psychosocial screening with a parent present significantly reduces disclosure of high-risk behaviours and should be avoided.

This child has moderate-to-severe diabetic ketoacidosis (DKA) with clinical signs of dehydration (tachycardia, delayed capillary refill, hypotension). The first priority in pediatric DKA management is fluid resuscitation with an isotonic crystalloid such as 0.9% sodium chloride to restore circulating volume, given cautiously (10-20 mL/kg over 1-2 hours) because of the risk of cerebral edema with overly rapid correction. Insulin therapy is started only after initial fluid resuscitation has begun, typically 1 hour later, to avoid precipitating a rapid osmotic shift and cerebral edema. Bicarbonate is not recommended in pediatric DKA as it increases the risk of cerebral edema and paradoxical CNS acidosis.

• A. Bicarbonate is not used in pediatric DKA management; it increases cerebral edema risk and worsens paradoxical CNS acidosis.
• C. Dextrose-containing fluids are not given until blood glucose falls below approximately 14-17 mmol/L; initial resuscitation requires isotonic saline without dextrose.
• D. Insulin boluses are avoided in pediatric DKA because they cause a rapid drop in osmolality, increasing the risk of cerebral edema.
• E. Subcutaneous insulin is not used in acute DKA due to unpredictable absorption in a dehydrated, poorly perfused patient; intravenous insulin infusion is used after fluids.