RNC-NIC Congenital Anomalies 3 — Questions and Answers
Question 1: A neonate with Trisomy 21 (Down syndrome) is found to have bilious vomiting on day 1 of life. Which diagnosis must be excluded first?
- Duodenal atresia (Correct answer)
- Pyloric stenosis
- Hirschsprung disease
- Malrotation with volvulus
Correct answer: Duodenal atresia
Duodenal atresia occurs in approximately 30% of neonates with Down syndrome and presents with bilious vomiting and a 'double-bubble' sign on X-ray.
Question 2: Which finding on abdominal X-ray is pathognomonic for duodenal atresia?
- Double-bubble sign with absent distal bowel gas (Correct answer)
- Multiple dilated loops of bowel with air-fluid levels
- Free air under the diaphragm
- Calcifications scattered throughout the abdomen
Correct answer: Double-bubble sign with absent distal bowel gas
The double-bubble sign represents air in the stomach and proximal duodenum with no distal gas, confirming complete duodenal obstruction.
Question 3: A neonate with Hirschsprung disease undergoes a rectal biopsy. Which histologic finding confirms the diagnosis?
- Absence of ganglion cells in the myenteric and submucosal plexuses (Correct answer)
- Hypertrophy of the internal anal sphincter only
- Presence of eosinophilic infiltrates in the bowel wall
- Hyperplasia of Meissner's plexus with abnormal cell morphology
Correct answer: Absence of ganglion cells in the myenteric and submucosal plexuses
Hirschsprung disease is defined by the absence of ganglion cells (aganglionosis) in the myenteric and submucosal plexuses of the affected bowel segment.
Question 4: A 3-day-old neonate presents with failure to pass meconium, abdominal distension, and bilious vomiting. Rectal examination produces an explosive release of stool and gas. This finding MOST suggests:
- Hirschsprung disease (Correct answer)
- Meconium ileus
- Jejunal atresia
- Imperforate anus
Correct answer: Hirschsprung disease
Explosive release of stool after rectal examination is a classic clinical sign of Hirschsprung disease, indicating the aganglionic segment relaxes with stimulus.
Question 5: Which condition is MOST commonly associated with meconium ileus at birth?
- Cystic fibrosis (Correct answer)
- Hirschsprung disease
- Trisomy 18
- Prune belly syndrome
Correct answer: Cystic fibrosis
Approximately 90% of neonates with meconium ileus have cystic fibrosis, caused by thick, inspissated meconium blocking the terminal ileum.
Question 6: A neonate with Pierre Robin sequence is placed prone immediately after birth. What is the primary rationale for this positioning?
- To allow the tongue to fall forward, relieving upper airway obstruction (Correct answer)
- To improve diaphragmatic excursion and ventilation
- To reduce intracranial pressure from associated hydrocephalus
- To facilitate drainage of oropharyngeal secretions
Correct answer: To allow the tongue to fall forward, relieving upper airway obstruction
Prone positioning uses gravity to pull the displaced tongue forward, relieving the glossoptosis that causes upper airway obstruction in Pierre Robin sequence.
Question 7: Which cleft type carries the highest risk of feeding difficulties and requires the most intensive nursing support?
- Cleft of the soft and hard palate without cleft lip (Correct answer)
- Unilateral cleft lip only
- Submucosal cleft palate
- Bilateral cleft lip without palate involvement
Correct answer: Cleft of the soft and hard palate without cleft lip
Cleft of the hard and soft palate prevents the infant from generating negative intraoral pressure for suction, causing the most severe feeding challenges.
RNC-NIC Congenital Anomalies 3
A neonate with Trisomy 21 (Down syndrome) is found to have bilious vomiting on day 1 of life.
Which diagnosis must be excluded first?