Arielle Kanters and Todd Ponsky

Introduction

Pyloric stenosis occurs in approximately 3 of every 1000 births in the United States and is a common cause of gastric outlet obstruction in infants. First described in 1911, the Ramstedt approach to pyloric stenosis repair (extramucosal pyloromyotomy) has been the surgical standard of care until recently. This technique involves splitting the antropyloric mass while leaving the mucosa intact. Morbidity of the Ramstedt procedure is less than 10% and the mortality rate is less than 0.5%. The laparoscopic modification of the Ramstedt procedure has gained great support in recent years, and some argue that it has improved morbidity and mortality rates compared with the traditional open approach.

Pyloric stenosis results from hypertrophy of the musculature surrounding the pylorus, but the etiology is currently unknown. Possible causes include compensatory work hypertrophy from increased gastric mucosa, neurologic degeneration, and aberrant endocrine signaling. Strong evidence exists for many of these theories, indicating a multifactorial etiology. Risk factors for pyloric stenosis include gender, race, family history, maternal age, birth order, and maternal feeding patterns.

Clinical Presentation and Diagnosis of Pyloric Stenosis

A diagnosis of pyloric stenosis depends on both patient history and physical examination. Most patients will initially be seen with progressive, nonbilious projectile vomiting at 2 to 8 weeks of age. Patients may show signs of metabolic alkalosis, dehydration, and malnutrition, depending on duration of symptoms. On examination, visible peristaltic waves at the epigastrium and a palpable mass in the left upper quadrant may be present when the abdominal wall is relaxed. The mass is typically olive shaped, smooth, hard, and about 1 to 2 cm in size (Fig. 10-1). The hypertrophied pylorus can also be appreciated using ultrasonography or an upper gastrointestinal (GI) contrast study.

Preoperative Imaging of Pyloric Stenosis

The ultrasonographic criteria for pyloric stenosis include an elongated pyloric channel (14 to 20 mm), an enlarged pyloric diameter (>12 mm), and a thickened muscle wall (>3 mm) (Fig. 10-2, A). A contrast study will demonstrate a distended stomach with a narrowed and elongated pyloric channel. These findings are often referred to as the “string” sign or “double track” sign. Upper GI studies can also show “shoulders” at the proximal end of the pylorus, indicating the hypertrophied muscle bulging into the gastric lumen, and a pyloric “beak” at the pyloric entrance to the antrum (Fig. 10-2, B).