NBME Pediatrics Form 3 - Answers & Explanations

Updated: Feb 25, 2020

1) Clostridium difficile

• Always consider Pseudomembranous colitis in a child with fever + bloody diarrhea who took antibiotics within the last 21 days

C.diff can also present with prolonged watery diarrhea

• Although clinical manifestations of Shigella can include fever and bloody diarrhea, this is mainly due to Shigella dysenteriae 1 or Shigella flexneri. Shigella sonnei presents as more of a watery diarrhea. There is also no mention of daycare, travel or immigration from a developing country, making C.diff colitis more likely


2) Cefotaxime • 3rd generation cephalosporins are 1st line for UTI in children


3) Extracardiac left-to-right shunt • PDA = extracardiac left to right blood shunting


4) Pertussis

• Paroxysmal phase: cough with inspiratory “whoop”, posttussive emesis

Dx: Pertussis culture or PCR

Tx: Macrolides


5) Posterior urethral valves

• Most common cause of urinary tract obstruction in newborn boys


6) Thrombocytopenia from platelet sequestration • Hemangioma, thrombocytopenia, and consumptive coagulopathy = Kasabach-Merritt syndrome (infrequent but fatal complication of rapidly growing vascular lesion in infants)


7) Cl 84, K 2.8, pH 7.50 • Hypokalemic hypochloremic metabolic alkalosis due to vomiting


8) Intravenous administration of dopamine

• “Cold septic shock” = septic shock that turned into cardiogenic shock (myocardial dysfunction from inflammatory cytokines)

• Dopamine → ↑ CO (inotropic), ↑ renal blood flow

• Patient is already receiving fluids and is still hypotonic (more IV fluids wouldn’t help)


9) Testing for Chlamydia trachomatis and Neisseria gonorrhoeae

• All patients below 25 years old that are sexually active should be screen for both chlamydia and gonorrhea


10) Intussusception • Sudden, intermittent abdominal pain • Most common cause of intestinal obstruction in children age 3-36 months


11) Physiologic jaundice • Presents on day 2-4 of life • Mothers blood group is B (rules out ABO hemolytic disease) • Mother is Rh ⊕ (rules out Rh hemolytic disease)

12) Trichophyton tonsurans • Tinea capitis (most common in African American children)

• Tx: oral griseofulvin or terbinafine


13) Impaired T-lymphocyte function • Recurring viral/fungal infections are due to T-cell dysfunction/absence


14) Trisomy 18 • Edward syndrome (trisomy 18) = prominent occiput, micrognathia, clenched fists with overlapping fingers, rocker bottom feet


15) Ventricular septal defect • VSD causes shunting of blood from left to right → ↑ blood in pulmonary circulation → ↑ blood in left atrium (LA) → enlargement of LA


16) Iron

• Hypochromic microcytic anemia

• Cow’s milk has low iron content and bioavailability - children shouldn’t be given cow’s milk until 12 months of age


17) Bronchiectasis

• Right middle lobe syndrome (chronic right middle lobe collapse, usually associated with bronchiectasis)

• Medication didn’t relieve symptoms ≠ asthma


18) Insertion of a nasogastric tube

• Polyhydramnios with excess oral secretions and coughing (most prominent after the first feed) = esophageal atresia (with distal TEF)

• Nasogastric tube will fail to pass into the stomach


19) Intravenous administration of 20 mL/kg of 0.9% saline

High-flow 0.9% normal salines initially recommended; add dextrose 5% when serum glucose is ≤ 200

• Add IV potassium if serum potassium ≤ 5.2


20) Ultrasonography of the abdomen

• WAGR syndrome: Wilms tumor, Aniridia (absence of iris), Genitourinary malformation, mental Retardation/intellectual disability

• Wilms tumor doesn’t cross midline (vs Neuroblastoma which crosses midline)



21) LarynxStridor = upper airway obstruction


22) Thyroid-stimulating