An 8-month-old boy is brought to clinic due to abdominal distension. The patient has had excessive straining and irritability with bowel movements since birth. He had been exclusively breastfed, and his symptoms worsened after transitioning to pureed foods. Vital signs are normal. Abdominal examination shows distension with mild tenderness to palpation. Bowel sounds are present, and there is no hepatosplenomegaly. Barium enema shows a relatively narrow rectum and rectosigmoid area. The rest of the colon proximal to this segment is significantly dilated. Colorectal biopsy of which of the following areas is most likely to reveal the underlying cause of this patient's condition?

Question

An 8-month-old boy is brought to clinic due to abdominal distension.  The patient has had excessive straining and irritability with bowel movements since birth.  He had been exclusively breastfed, and his symptoms worsened after transitioning to pureed foods.  Vital signs are normal.  Abdominal examination shows distension with mild tenderness to palpation.  Bowel sounds are present, and there is no hepatosplenomegaly.  Barium enema shows a relatively narrow rectum and rectosigmoid area.  The rest of the colon proximal to this segment is significantly dilated.  Colorectal biopsy of which of the following areas is most likely to reveal the underlying cause of this patient's condition?

Quizplus · Accepted Answer

11ec160b_394f_b8ae_9249_b726e71e30a5_MD0001_00 This infant with chronic constipation and abdominal distension has barium enema findings suggestive of Hirschsprung disease (HD). HD is a congenital disorder in which neural crest cells fail to migrate to the bowel wall during embryogenesis. These cells normally develop into ganglion cells of the submucosal (Meissner) and myenteric (Auerbach) plexus. In HD, the affected colon lacks parasympathetic ganglia and is therefore unable to relax. Because the neural crest cells migrate caudally along the bowel, the rectosigmoid area is most commonly involved. Typical presentation is in the neonatal period with delayed passage of meconium and signs of bowel obstruction (eg, bilious emesis, abdominal distension). However, disease severity correlates with the length of nonfunctional bowel. Therefore, those with a short aganglionic segment may go undiagnosed with chronic, refractory constipation for months or years, as in this case. Characteristic findings on contrast enema include a narrowed rectosigmoid area (due to chronic contraction) and a dilated bowel proximal to the obstruction. Rectal suction biopsy is the gold standard for the diagnosis of HD and should include the submucosa of the rectum (ie, narrowed segment), which is the most superficial layer that demonstrates the absence of ganglion cells (ie, submucosal plexus). Absence of ganglia between the longitudinal and circular layers of the muscularis externa (ie, myenteric plexus) can also be seen on full-thickness biopsies. Educational objective: Absence of the submucosal (Meissner) and myenteric (Auerbach) plexuses in Hirschsprung disease causes the affected rectosigmoid region to become narrowed. The submucosa of the narrowed area is the most superficial layer where the absence of ganglion cells can be confirmed during biopsy procedures.

An 8-Month-Old Boy Is Brought to Clinic Due to Abdominal