A 3-week-old infant is brought to the emergency department with a history of forceful, projectile vomiting after feedings and signs of weight loss. On assessment, the nurse palpates a small, olive-shaped mass in the upper abdomen. Which condition does this clinical picture most likely indicate?

A. Overstimulation of parasympathetic nerves resulting in rapid bowel transit is incorrect because Hirschsprung’s disease is characterized by decreased or absent bowel motility, not increased motility. Rapid transit would lead to diarrhea rather than constipation and failure to pass meconium.

B. Absence of ganglionic nerve cells in a portion of the colon, causing a lack of peristalsis is correct because Hirschsprung’s disease is a congenital disorder caused by aganglionosis. The affected segment of the colon lacks enteric (Meissner and Auerbach) ganglion cells, resulting in failure of peristalsis, functional obstruction, and accumulation of stool proximal to the affected area.

C. Obstruction caused by hypertrophy of intestinal smooth muscle is incorrect because this mechanism is more consistent with conditions such as pyloric stenosis, not Hirschsprung’s disease. Hirschsprung’s is a neurologic defect, not a muscle hypertrophy problem.

D. Inflammation of the intestinal mucosa leading to motility loss is incorrect because Hirschsprung’s disease is not an inflammatory condition. While inflammation may occur secondary to bowel obstruction, it is not the primary pathophysiologic cause.

A. Gently assess the ear and check for redness, swelling, or drainage is correct. The infant’s symptoms, tugging at the ear, inconsolable crying, and increased pain when lying down, are classic signs of acute otitis media (ear infection). A careful, gentle assessment of the external ear and ear canal for redness, swelling, or drainage helps determine the source of pain and guides appropriate treatment.

B. Administer pain medication without further assessment is incorrect because pain management should follow an assessment to identify the underlying cause. Treating pain without understanding the source may delay diagnosis and appropriate treatment, such as antibiotics if indicated.

C. Assume the pain is generalized to the entire head is incorrect because infants often cannot verbalize pain location, but the pattern of ear tugging and positional crying provides important diagnostic clues. Making assumptions without assessment risks misdiagnosis.

D. Ask the infant to point to where it hurts is incorrect because a 9-month-old cannot reliably indicate the location of pain, making observation and gentle physical assessment essential.