A 25-hour-old boy is evaluated in the nursery due to vomiting. The patient was born at 36 weeks gestation via spontaneous vaginal delivery to a 24-year-old primigravida. His mother was attempting to breastfeed when he developed "bright green" vomiting. She tried to feed again, but the vomiting recurred. The patient has not yet had a bowel movement. Temperature is 36.7 C (98.1 F) and pulse is 170/min. Examination shows a crying infant with a distended abdomen. Rectal examination shows normal tone and caliber with no stool in the rectal vault. Radiographs of the abdomen reveal markedly dilated loops of small bowel with no rectal air and no free air. Which of the following is the most likely cause of this patient's symptoms?

Question

A 25-hour-old boy is evaluated in the nursery due to vomiting.  The patient was born at 36 weeks gestation via spontaneous vaginal delivery to a 24-year-old primigravida.  His mother was attempting to breastfeed when he developed "bright green" vomiting.  She tried to feed again, but the vomiting recurred.  The patient has not yet had a bowel movement.  Temperature is 36.7 C (98.1 F) and pulse is 170/min.  Examination shows a crying infant with a distended abdomen.  Rectal examination shows normal tone and caliber with no stool in the rectal vault.  Radiographs of the abdomen reveal markedly dilated loops of small bowel with no rectal air and no free air.  Which of the following is the most likely cause of this patient's symptoms?

Quizplus · Accepted Answer

11ec25c8_d678_ca96_bc81_b3679b138d6c_MD0003_00 Nearly all healthy newborns pass meconium within 24 hours of birth. This patient's delayed meconium passage, in addition to bilious emesis, raises concern for intestinal obstruction. The most likely cause in a patient with normal rectal tone and caliber is meconium ileus. Meconium ileus is typically characterized by blockage of the terminal ileum by inspissated meconium. Most cases occur in patients with cystic fibrosis (CF), a genetic disorder resulting in the accumulation of thick, tenacious secretions in multiple organs, including the gastrointestinal tract. Meconium ileus may be the earliest feature of CF and presents in the first couple of days of life with abdominal distension and failure to pass meconium. As seen in this patient, bilious emesis may also occur. bilious emesis The first step in the workup of suspected intestinal obstruction is an abdominal x-ray to identify the level of impaction and potential complications (eg, free air due to perforation). Imaging of meconium ileus classically reveals dilated loops of small bowel proximal to the obstruction with minimal or absent air distally in the colon and rectum. A soap-bubble gas pattern may be present in the ileum due to mixing of meconium with air. Water-soluble contrast enema revealing microcolon is diagnostic of meconium ileus. dilated loops of small bowel microcolon (Choice A) Hirschsprung disease, caused by failure of normal intestinal neural crest migration, is characterized by a distal aganglionic colonic segment and a proximally dilated colonic segment (megacolon). Although it can cause bilious emesis and delayed passage of meconium, dilated loops of large bowel would be expected on x-ray (rather than small bowel, as in this patient), and a tight anal sphincter would be present on rectal examination (rather than normal tone, as in this patient). megacolon (Choice B) Bowel obstruction due to a fibrotic stricture in the terminal ileum is seen with Crohn disease. Strictures occur due to chronic inflammation and would not be seen in a newborn. (Choice C) Ileus due to prematurity-related necrosis describes necrotizing enterocolitis. Although it can cause abdominal distension and bilious vomiting, it typically occurs in infants born at gestational age <32 weeks, presents with bloody diarrhea, and is associated with pneumatosis intestinalis (air dissecting the bowel wall) on X-ray. (Choice E) Intussusception (telescoping of bowel into itself) typically occurs in children age 6-36 months and presents with episodic abdominal pain (eg, legs drawn up to chest), vomiting, and bloody stools. Intussusception is rare in newborns. Educational objective: Meconium ileus should be suspected in newborns with failure to pass meconium, in addition to bilious emesis and dilated loops of small bowel on imaging (ie, terminal ileum obstruction). Most newborns with meconium ileus have cystic fibrosis. References: Meconium ileus in cystic fibrosis. (http://www.ncbi.nlm.nih.gov/pubmed/28986020) Meconium ileus. (http://www.ncbi.nlm.nih.gov/pubmed/29487495)

A 25-Hour-Old Boy Is Evaluated in the Nursery Due to Vomiting