Examkin

Question

Difficulty: EasyPediatric Gastrointestinal Disorders

An 11-week-old male infant is brought to the pediatric clinic by his parents because he has not had a bowel movement for the past six days. The parents report that his stools are typically small and hard, and his abdomen frequently appears bloated. They mention that after birth, he did not pass his first stool until he was almost two days old. The infant is exclusively formula-fed. Vital signs are within normal limits for his age. Physical examination demonstrates a distended but soft abdomen with normoactive bowel sounds. Digital rectal examination reveals a tight anal sphincter. Upon withdrawal of the examiner's finger, there is an explosive release of gas and foul-smelling stool. Which of the following is the most definitive test to confirm the diagnosis in this patient?

  1. Rectal suction biopsyAnswer
  2. B
    Contrast enema
  3. C
    Empiric polyethylene glycol therapy
  4. D
    Stool culture and analysis
  5. E
    Abdominal computed tomography scan

Answer

Rectal suction biopsy
The correct answer is rectal suction biopsy. The infant's presentation of delayed passage of meconium, chronic constipation, abdominal distension, and the classic 'squirt sign' (explosive expulsion of gas and stool after a digital rectal exam) are highly suggestive of Hirschsprung disease. This condition results from the failure of neural crest cells to migrate to the distal colon, leaving an aganglionic segment that remains tonically contracted and causes a functional obstruction. Although a contrast enema is frequently the first imaging study performed to identify a transition zone, the gold standard and most definitive diagnostic test is a rectal suction biopsy. This procedure evaluates the submucosal (Meissner) plexus to definitively confirm the absence of ganglion cells.

Step-by-Step Solution

1
Analyze the patient's clinical presentation.
The patient has a history of delayed meconium passage (>48 hours), chronic severe constipation, abdominal distension, and an explosive release of stool upon digital rectal exam (the 'squirt sign').
Identifying these classic signs points heavily toward Hirschsprung disease, characterized by an aganglionic segment of the distal colon.
2
Determine the necessary diagnostic workup for the suspected condition.
While initial imaging like a contrast enema might be performed to visualize a transition zone, a tissue sample is required for a definitive diagnosis.
The defining pathophysiological feature is the absence of ganglion cells, which can only be confirmed histologically via a rectal suction biopsy.

Key Concept

Diagnosis of Hirschsprung disease
Rate this question

Topics

Pediatric Gastrointestinal Disorders

More questions from this topic