A 10-day-old small-for-gestational-age neonate presents with abdominal distention, diarrhea, nonbilious emesis, and a palpable abdominal mass. The most likely diagnosis is which of the following?

A 10-day-old small-for-gestational-age neonate presents with abdominal distention, diarrhea, nonbilious emesis, and a palpable abdominal mass. The most likely diagnosis is which of the following?

• A. Meconium ileus
• B. Intussusception
• C. Pyloric stenosis
• D. Lactobezoar

Answer: (D)

Lactobezoar formation is the scenario this question is testing. In newborns, especially those who are small for gestational age and fed formula or concentrated feeds, insidiously formed clusters of undigested milk curds can accumulate in the stomach or proximal intestine because gastric emptying is immature and the curd becomes inspissated. This creates an intraluminal obstruction that presents with abdominal distention, vomiting that is nonbilious (originating proximal to the bile ducts), diarrhea from irritated bowel and poor feeding, and a palpable abdominal mass from the obstruction itself or accumulated material. The age—about the first week of life—fits well for lactobezoar, and being small for gestational age increases risk when formula feeds are used. By contrast, meconium ileus would typically appear very early in life with failure to pass meconium and often bilious emesis, and intussusception usually occurs later in infancy with episodic pain and sometimes currant jelly stools rather than a consistent proximal obstruction picture in a neonate. Pyloric stenosis generally presents later, around several weeks of age, with projectile nonbilious vomiting and a palpable olive in the epigastrium. So the presentation aligns best with a lactobezoar: an intraluminal milk curd mass causing proximal obstruction in a neonate fed formula, particularly in a small-for-gestational-age infant.

Lactobezoar formation is the scenario this question is testing. In newborns, especially those who are small for gestational age and fed formula or concentrated feeds, insidiously formed clusters of undigested milk curds can accumulate in the stomach or proximal intestine because gastric emptying is immature and the curd becomes inspissated. This creates an intraluminal obstruction that presents with abdominal distention, vomiting that is nonbilious (originating proximal to the bile ducts), diarrhea from irritated bowel and poor feeding, and a palpable abdominal mass from the obstruction itself or accumulated material. The age—about the first week of life—fits well for lactobezoar, and being small for gestational age increases risk when formula feeds are used.

By contrast, meconium ileus would typically appear very early in life with failure to pass meconium and often bilious emesis, and intussusception usually occurs later in infancy with episodic pain and sometimes currant jelly stools rather than a consistent proximal obstruction picture in a neonate. Pyloric stenosis generally presents later, around several weeks of age, with projectile nonbilious vomiting and a palpable olive in the epigastrium.

So the presentation aligns best with a lactobezoar: an intraluminal milk curd mass causing proximal obstruction in a neonate fed formula, particularly in a small-for-gestational-age infant.