A 50-hour-old boy is in the nursery with several episodes of bilious emesis. He is unable to tolerate breast or bottle feeds. He has urinated twice but has not passed meconium. The boy was born to a primigravid woman at 39 weeks gestation; birth was by cesarean section due to failure to progress. The pregnancy was uncomplicated and prenatal laboratory results were normal. The mother declined genetic testing during the pregnancy. Membranes ruptured spontaneously 2 hours before delivery and the fluid was clear. Apgar scores were 9 at both 1 and 5 minutes. Weight, length, and head circumference are average for gestational age. Examination shows a non-dysmorphic boy with a markedly distended abdomen. The anus is open and normally positioned. No stool is palpable in the rectal vault. A nasogastric tube is placed for decompression and intravenous fluids are initiated. Abdominal x-ray shows multiple dilated loops of large bowel and no air in the rectum. Contrast enema shows a normal caliber rectosigmoid colon and a dilated descending colon. Which of the following is the best test to confirm the underlying diagnosis?

Question

A 50-hour-old boy is in the nursery with several episodes of bilious emesis.  He is unable to tolerate breast or bottle feeds.  He has urinated twice but has not passed meconium.  The boy was born to a primigravid woman at 39 weeks gestation; birth was by cesarean section due to failure to progress.  The pregnancy was uncomplicated and prenatal laboratory results were normal.  The mother declined genetic testing during the pregnancy.  Membranes ruptured spontaneously 2 hours before delivery and the fluid was clear.  Apgar scores were 9 at both 1 and 5 minutes.  Weight, length, and head circumference are average for gestational age.  Examination shows a non-dysmorphic boy with a markedly distended abdomen.  The anus is open and normally positioned.  No stool is palpable in the rectal vault.  A nasogastric tube is placed for decompression and intravenous fluids are initiated.  Abdominal x-ray shows multiple dilated loops of large bowel and no air in the rectum.  Contrast enema shows a normal caliber rectosigmoid colon and a dilated descending colon.  Which of the following is the best test to confirm the underlying diagnosis?

Quizplus · Accepted Answer

Explanation: 11ec2b69_c159_0665_8f63_b7d2164c42bc_MD0005_00 Full-term infants normally pass meconium within 48 hours of birth. Failure to pass meconium is usually pathologic and can lead to abdominal distension, poor feeding, and bilious emesis. Initial evaluation consists of abdominal x-ray to rule out free intraperitoneal air and to evaluate the bowel gas pattern. The presence of multiple dilated bowel loops and the absence of rectal air are concerning for distal bowel obstruction. Contrast enema is performed to delineate the level of obstruction in the distal intestinal tract. The classic finding for Hirschsprung disease (HD, congenital aganglionic megacolon) is a transition zone between a normal or narrow caliber rectosigmoid (aganglionic segment) and a normally innervated but markedly dilated descending colon (Image). bilious emesis distal bowel obstruction The absence of ganglion cells on rectal mucosal suction biopsy definitively confirms HD. Treatment consists of surgical resection of the aganglionic segment followed by anastomosis of normal bowel to the anus. Up to 25% of patients with HD have another congenital anomaly (eg, renal) and approximately 10% of patients with HD have a chromosomal defect (eg, Down syndrome). (Choice A) Abdominal ultrasound is the preferred imaging modality for pyloric stenosis, which typically presents as nonbilious emesis without abdominal distension in infants age 4-8 weeks. (Choice B) Anorectal manometry is a motility test that measures anal sphincter pressure, anorectal inhibitory reflex, and rectal compliance and sensation. This test can be helpful as a screening test in older infants or children as failure of internal anal sphincter relaxation during rectal distension suggests HD. However, it is less accurate than rectal biopsy (especially in neonates). (Choice D) Sweat chloride test is the gold standard test for cystic fibrosis (CF). The tenacious secretions in CF can cause meconium ileus as the inspissated stool is difficult to propel, resulting in impaction in the ileum and a narrow, underused "microcolon". CF is not associated with HD. (Choice E) Upper gastrointestinal series is the best test for diagnosing malrotation with midgut volvulus, which can cause bilious emesis but is not associated with delayed meconium passage. In addition, abdominal x-ray may show a nasogastric tube in a displaced duodenum rather than dilated loops of large bowel. Educational objective: Hirschsprung disease causes delayed meconium passage and abdominal distension due to lack of innervation in the rectosigmoid colon. Initial workup typically shows distal bowel obstruction on x-ray and a "transition zone" on contrast enema. Rectal suction biopsy is the gold standard diagnostic test. References: Rectal suction biopsy to exclude the diagnosis of Hirschsprung disease. (http://www.ncbi.nlm.nih.gov/pubmed/22922333) Hirschsprung's disease: Role of rectal suction biopsy - data on 216 specimens. (http://www.ncbi.nlm.nih.gov/pubmed/20975783) Rectal biopsy for Hirschsprung's disease--are we performing too many? (http://www.ncbi.nlm.nih.gov/pubmed/20397119)

A 50-Hour-Old Boy Is in the Nursery with Several Episodes