Although reports date back to the early 1600s, Harald Hirschsprung is credited as the first person to describe hypertrophic pyloric stenosis (HPS) in 1887.

Hirschsprung reported on 2 cases of term infants who suddenly began vomiting and losing significant amounts of weight. He found at autopsy that both of his young patients had hypertrophied and elongated pyloric channels.¹

As the pathology became better understood, a variety of surgical treatments emerged as attempts to correct this disease process.

In 1912, German surgeon Conrad Ramstedt developed the pyloromyotomy, which is the foundation of surgical treatment today.²

The pyloric channel is the distal portion of the stomach that connects to the first portion of the duodenum.

At the distal portion of the pyloric channel, there is a circular layer of smooth muscle, which comprises the pyloric sphincter.

The pyloric sphincter controls the rate of stomach emptying and prevents regurgitation of chyme from the duodenum back into the stomach.

The normal pyloric muscle thickness is ≤2 mm.

Males are affected approximately 4 times more frequently than females.

There is also evidence of a genetic predisposition, as siblings of children with HPS are at approximately 15 times greater risk of also developing the condition.³

Some environmental causes have been linked to development of HPS.

Erythromycin is associated with HPS with a postulated mechanism that its promotility effects can lead to hypertrophy of the sphincter muscle.

It is paramount to distinguish this from infants with bilious emesis, which can suggest a multitude of other pathologies that will be discussed in other chapters.

Unlike other etiologies, patients with HPS are typically hungry and eager to feed after episodes of emesis.

The average age of patients presenting with HPS is between third and sixth week of life.

The classic physical examination finding is a palpable “olivelike” mass, although oftentimes this is hard to elicit unless the baby is resting comfortably.