A 14-day-old girl is brought to the emergency department for diarrhea. Her mother reports that the patient began having “explosive” diarrhea 6 hours ago. The patient has little interest in feeding since leaving the hospital after her birth and has not yet regained her birth weight. Her immediate postnatal period was otherwise significant for 2 episodes of bilious vomiting that resolved with the temporary use of a nasogastric tube and expulsion of stool during a digital rectal exam. The patient passed meconium on the 3rd day of life. Her temperature is 101.8°F (38.8°C), blood pressure is 58/37 mmHg, pulse is 148/min, and respirations are 38/min. On physical exam, the patient appears to be in moderate distress. She has no dysmorphic features and she has a normal S1/S2 without any murmurs, rubs, or gallops. Her abdomen is firm and distended. A digital rectal exam reveals a tight anal sphincter and precipitates a release of gas and liquid stool. Her abdominal radiograph can be seen in Figure A. Which of the following is the most accurate test to diagnose this patient’s condition?
Upper gastrointestinal series
Rectal suction biopsy
Contrast enema
Intraoperative cholangiogram
Rectal suction biopsy
This neonatal patient presents with bilious vomiting, failure to thrive, colonic distension on an abdominal radiograph, and new fever and tachycardia, which suggests a diagnosis of Hirschsprung disease complicated by enterocolitis. A rectal suction biopsy is the most accurate test to diagnose Hirschsprung disease.

Hirschsprung disease presents in the neonatal period with bilious vomiting, failure to pass meconium in the first 48 hours of life, failure to thrive, and temporary relief of the intestinal obstruction by digital rectal exam. The most severe neonatal complication of Hirschsprung disease is Hirschsprung-associated enterocolitis, which presents in the first few weeks to months of life with explosive diarrhea, fever, and abdominal pain/distension. The most appropriate first step to diagnose Hirschsprung disease is a contrast enema, which may visualize a “transition zone” where the caliber of the intestine switches from the dilated proximal colon to the narrowed aganglionic segment. The most accurate test is a rectal suction biopsy, which will show a lack of ganglion cells. Surgical removal of the aganglionic portion of the colon is preferred management.

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 demonstrating diffuse proximal colonic distension (red circle) with a paucity of air in the rectosigmoid. This finding suggests a diagnosis of Hirschsprung disease.

Incorrect Answers:
Answer A: A contrast enema is both a diagnostic and therapeutic intervention for intussusception. It may also be used in the workup of bilious emesis to help differentiate between Hirschsprung disease and meconium ileus, but it is not the most accurate test.

Answer B: Genetic testing would be used to diagnose cystic fibrosis, which is associated with meconium ileus. Although meconium ileus presents with delayed passage of meconium (> 48 hours of life), meconium ileus is not relieved by a digital rectal exam. Treatment is with irrigation and removal of the meconium.

Answer C: Intraoperative cholangiogram is the gold standard for diagnosing biliary atresia. Biliary atresia presents with jaundice, pale stools or dark urine, and hepatomegaly over the first week to 2 months of life. Treatment is with urgent surgical intervention to prevent liver failure.

Answer E: Upper gastrointestinal series is used to diagnose intestinal malrotation, as the ligament of Treitz can be visualized on the right side of the abdomen. Malrotation may present with bilious vomiting if the malrotation has been complicated by midgut volvulus, but it would not be relieved by digital disimpaction. Treatment is with surgical derotation of the volvulus.

Bullet Summary:
The most accurate test to diagnose Hirschsprung disease is a rectal suction biopsy to demonstrate the absence of ganglion cells.