Chapter 40: Pyloric Stenosis

Key Points

History

The first clinical description of pyloric stenosis is attributed to Hildanus in 1627. Although sporadic reports of infants with gastric outlet obstructive symptoms followed his initial description, it was not until the seminal work of Harald Hirschsprung in 1888 that infantile hypertrophic pyloric stenosis (HPS) was established as a distinct clinical entity. The first successful surgery followed shortly thereafter in 1899, when Lobker performed a gastrojejunostomy to successfully treat an infant with HPS. General acceptance of this procedure was not favorable due to an attendant postoperative mortality as high as 50%. Nicoll (1906) and Fredet (1907) working independently developed a technique of extramucosal pyloroplasty that would provide the foundation for pyloromyotomy first described in 1912 by Ramstedt. Although various incisions have been used to access the pylorus, the Ramstedt procedure, as it is frequently called, has remained the surgical standard until the present. Recently, the laparoscopic approach originally described by Allain and colleagues in 1991 has gained immense popularity. Laparoscopic pyloromyotomy has supplanted the open procedure as the new standard in many pediatric centers. Currently, the morbidity and mortality of pyloromyotomy regardless of approach in experienced hands is less than 10% and 0.5%, respectively.

Pathophysiology

Pyloric stenosis is one of the most common surgical conditions of early infancy presenting in approximately 3 per 1000 live births in the United States. Despite this high prevalence, the precise etiology of the condition remains poorly understood. Family history, sex, birth order, and maternal feeding patterns have all been implicated as potential risk factors. Numerous theories for the pathogenesis of pyloric stenosis have been proposed, but none has achieved general acceptance. These theories fall into 3 principal categories: (1) compensatory work hypertrophy, (2) neurologic degeneration or immaturity, and (3) abnormal endocrine or growth factor signals. Some authors have suggested that milk curds developing in the stomach can obstruct the pyloric channel leading to redundancy in the pyloric mucosa and compensatory pyloric muscle hypertrophy. Other investigators have theorized that various neural components in the pyloric antrum may be immature or defective leading to increased muscle size. Some of these theories include the deficiency of nitric oxide synthase, decreased interstitial cells of Cajal (pacemaker cells of the gut), and diminished expression of neural cell adhesion molecule (NCAM). Other authors have implicated gastrointestinal endocrine or paracrine factors such as gastrin hypersecretion in either the infant or the mother as the stimulus toward muscle hypertrophy. The familial occurrence of this condition in some patients also implicates genetic factors in the etiology. Due to the strong evidence supporting each of these major theories, the etiology is likely multifactorial and yet to be determined.

Diagnostic Principles