A four-week-old former full-term infant is brought to the emergency department by his parents for vomiting. The mother explains that she exclusively breastfeeds the infant and that for the past two weeks he has vomited after every meal but still appears hungry. She describes that the vomiting has increased in intensity over the last week, and the infant now forcefully vomits. Upon further questioning, the mother describes the emesis as nonbilious and consisting of only breastmilk. However, today the emesis contained what appeared to be bright red blood. The patient's mother received routine prenatal care, and the delivery and post-natal course were uneventful. On physical examination, the infant is afebrile and appears somnolent, the fontanelle appears slightly sunken, lung sounds are clear to auscultation, and a 1 cm mass is palpated in the epigastric area of the abdomen. Serum laboratory results reveal the following:
D) Tear in the esophageal mucosa
This is a presentation of infantile hypertrophic pyloric stenosis (IHPS), which is a hypertrophy of the pyloric sphincter muscle. This condition usually presents between three and five weeks of age with immediate postprandial vomiting that is forceful and nonbilious. The infant demands to be refed soon after the vomiting occurs. A small olive-shaped mass can classically be palpated in the right upper quadrant of the abdomen at the lateral edge of the rectus abdominis muscle. The repetitive vomiting creates a hypochloremic, hypokalemic metabolic alkalosis as is demonstrated in the vignette. In this infant, the forceful vomiting resulted in a Mallory-Weiss tear, which is a tear in the esophageal mucosa, resulting in blood in the emesis.
Answer A: Deficiency of clotting factors, is incorrect. A deficiency of clotting factors would most likely lead to additional manifestations of bleeding without the suggestion of infantile hypertrophic pyloric stenosis.
Answer B: Ingestion of a foreign body, is incorrect. The vignette does not suggest ingestion of a foreign body which would be unlikely in such a young infant unless there were a toddler sibling who might be involved. The hypochloremic, hypokalemic metabolic alkalosis is also inconsistent with foreign body ingestion.
Answer C: Invasive bacterial infection, is incorrect. The vignette is most consistent with a gastrointestinal etiology, and the lack of fever or diarrhea makes an invasive bacterial infection less likely.
Answer E: Ulceration of gastric mucosa, is incorrect. This would be seen in peptic ulcer disease which is not suggested by this clinical vignette.
Key Learning Point
Forceful vomiting can result in a Mallory-Weiss tear, which is a tear in the esophageal mucosa that results in hematemesis.
