A 3-day-old boy is brought to the emergency department due to poor feeding, emesis, and lethargy over the last 24 hours. The patient was born via uncomplicated spontaneous vaginal delivery to a 30-year-old woman who had a normal pregnancy. The boy was discharged from the newborn nursery yesterday and was breastfeeding exclusively until the onset of symptoms. Stool and urine output were normal while he was in the newborn nursery. The patient is afebrile and normotensive but tachycardic and tachypneic. He appears dehydrated, and the abdomen is distended. The patient vomits during the examination, and the vomitus is shown in the exhibit.

On laparotomy, fibrous bands are seen extending from the cecum and right colon to the retroperitoneum, causing extrinsic compression of the duodenum. Which of the following embryologic processes most likely failed in this patient?

Question

A 3-day-old boy is brought to the emergency department due to poor feeding, emesis, and lethargy over the last 24 hours. The patient was born via uncomplicated spontaneous vaginal delivery to a 30-year-old woman who had a normal pregnancy. The boy was discharged from the newborn nursery yesterday and was breastfeeding exclusively until the onset of symptoms. Stool and urine output were normal while he was in the newborn nursery. The patient is afebrile and normotensive but tachycardic and tachypneic. He appears dehydrated, and the abdomen is distended. The patient vomits during the examination, and the vomitus is shown in the exhibit.

On laparotomy, fibrous bands are seen extending from the cecum and right colon to the retroperitoneum, causing extrinsic compression of the duodenum. Which of the following embryologic processes most likely failed in this patient?

On laparotomy, fibrous bands are seen extending from the cecum and right colon to the retroperitoneum, causing extrinsic compression of the duodenum.  Which of the following embryologic processes most likely failed in this patient?

Quizplus · Accepted Answer

Around 6 weeks gestation, the midgut (supplied by the superior mesenteric artery) herniates through the umbilical ring in order to grow rapidly. During this process, the midgut rotates 90 degrees counterclockwise. Following additional growth, the midgut returns to the abdominal cavity at 8-10 weeks gestation and turns an additional 180 degrees counterclockwise (270 degrees total). Subsequently, the gut is fixed to the posterior abdomen on a wide-based mesentery. Incomplete counterclockwise rotation (eg, 180 degrees) will result in midgut malrotation. The cecum will rest in the right upper quadrant instead of the right lower quadrant (RLQ). Additionally, Ladd's (fibrous) bands connect the retroperitoneum in the RLQ to the right colon/cecum by passing over the second part of the duodenum, causing intestinal obstruction in the process. Obstruction manifests as bilious emesis during the first days of life. In addition, because the mesenteric base is abnormally narrowed, the mesentery is vulnerable to twisting around the superior mesenteric artery. The twisting, referred to as midgut volvulus, compromises intestinal perfusion and may lead to life-threatening bowel necrosis. (Choice A) Failure of gut recanalization is a possible mechanism for development of duodenal atresia (distension of stomach and duodenum on X-ray). Ladd's bands are not found in this condition. (Choice B) Failure of ventral and dorsal pancreatic buds to fuse at 8 weeks gestation results in pancreas divisum. However, this condition is usually asymptomatic and an incidental finding on imaging study or autopsy. (Choice D) Failure of neural crest cell migration in the gut causes aganglionic sigmoid colon/rectum. The affected bowel segments cannot relax and are therefore narrow and obstructive. Hirschsprung disease presents in the neonatal period with delayed passage of meconium, abdominal distension, and bilious emesis. (Choice E) The omphalomesenteric duct connects the midgut lumen with the yolk sac. Failed obliteration of the duct causes vitelline fistula (complete failure) or a Meckel diverticulum (partial failure). If symptomatic, Meckel diverticulum most commonly presents with painless lower gastrointestinal bleeding without emesis. Educational objective: Intestinal malrotation results when the midgut undergoes incomplete embryological counterclockwise rotation. It can present as intestinal obstruction (due to compression by the adhesive bands) and midgut volvulus (intestinal ischemia due to twisting around the blood vessels). __________ References: Intestinal malrotation and catastrophic volvulus in infancy (http://www.ncbi.nlm.nih.gov/pubmed/22325550)

A 3-Day-Old Boy Is Brought to the Emergency Department Due