A 2-day-old boy has an episode of vomiting in the hospital nursery. The vomitus was described as “bright green” without any traces of blood. The patient has urinated several times since he was born but has not passed any stool. He was born at 37 weeks of gestation to a 38-year-old G3P3 woman. The pregnancy was uncomplicated and the patient’s mother refused all prenatal testing. The patient’s 2 older siblings are both healthy. His temperature is 98.6°F (37°C), blood pressure is 67/43 mmHg, pulse is 135/min, and respirations are 34/min. On physical exam, the patient has upslanting palpebral fissures, epicanthal folds, and a single transverse palmar crease. His abdomen is non-tender, firm, and distended. Bowel sounds are hypoactive. Digital rectal exam evacuates a small amount of stool and flatulence. A nasogastric tube is placed to decompress the stomach. The patient’s abdominal radiograph can be seen in Figure A. Which of the following is the most likely diagnosis?
Pyloric stenosis
Intestinal malrotation
Hirschsprung disease
Meconium ileus
Hirschsprung disease
This pediatric patient presents with features of Down syndrome (trisomy 21), bilious vomiting, and colonic distention on an abdominal radiograph, which suggests a diagnosis of Hirschsprung disease.

Hirschsprung disease is associated with Down syndrome and presents with bilious vomiting, failure to pass meconium in the first 48 hours of life, and abdominal distension. A digital rectal exam may temporarily relieve the obstruction and lead to the expulsion of gas and stool (the “squirt sign”). Abdominal radiography typically demonstrates signs of distal intestinal obstruction such as proximal dilation and an absence of air in the rectum. Contrast enema may reveal a transition zone between the dilated proximal megacolon and the narrow rectosigmoid colon. A biopsy can confirm the diagnosis. Treatment is with surgical removal of the defective segment of the bowel.

Kessman reviews the evidence regarding the diagnosis and treatment of Hirschsprung disease. She discusses how the diagnosis can be made using a rectal suction biopsy. She recommends monitoring patients closely for enterocolitis for years after surgical treatment.

Figure/Illustration A is an abdominal radiograph that demonstrates colonic distension (red circle). This finding is consistent with a diagnosis of Hirschsprung disease.

Incorrect Answers:
Answer A: Duodenal atresia is associated with Down syndrome (trisomy 21) and may also present in the first 48 hours of life with bilious vomiting. The abdominal radiograph will demonstrate the “double bubble” sign, which reflects air trapping in the stomach and first portion of the duodenum. Treatment is with the surgical opening of the atretic segment.

Answer C: Intestinal malrotation may preset with bilious vomiting in a neonate due to the development of a midgut volvulus. An abdominal radiograph may show the extension of the nasogastric tube into an abnormally positioned duodenum and would not show diffuse colonic distension. Treatment is with surgical derotation of the volvulus.

Answer D: Meconium ileus is associated with cystic fibrosis and also presents with delayed (> 48 hours) passing of meconium. The distal obstruction in these patients will not be temporarily relieved by a digital rectal exam. Contrast enema will demonstrate microcolon involving the entire large bowel. Treatment is with irrigation and removal of the meconium.

Answer E: Pyloric stenosis usually presents in the first 3-6 weeks of life with post-prandial, nonbilious, projectile vomiting and a palpable olive-shaped mass in the epigastrium. This patient is presenting at just 2 days of life and has bilious vomiting. Treatment is with surgical release of the stenosis.

Bullet Summary:
Hirschsprung disease is associated with Down syndrome (trisomy 21) and presents with retention of stool that can be relieved by digital disimpaction, bilious vomiting, and colonic distention on abdominal radiography.