What are the typical presentations of pyloric stenosis?

From the Guidelines

Pyloric stenosis typically presents in infants 2-8 weeks of age with progressive, projectile, non-bilious vomiting that occurs shortly after feeding. This condition is characterized by a gradual worsening of symptoms over days to weeks, with the vomiting becoming more forceful and occurring after most or all feedings 1. The infant remains hungry and eagerly feeds again after vomiting, which is a key distinguishing feature from other causes of vomiting.

Clinical Presentation

The clinical presentation of pyloric stenosis includes:

• Progressive, projectile, non-bilious vomiting
• Vomiting that occurs shortly after feeding
• Visible gastric peristaltic waves moving from left to right across the upper abdomen
• A palpable olive-shaped mass in the right upper quadrant, representing the hypertrophied pylorus
• Signs of dehydration, including decreased urine output, dry mucous membranes, sunken fontanelles, and lethargy

Laboratory Findings

Laboratory findings often show hypochloremic, hypokalemic metabolic alkalosis due to loss of hydrochloric acid from persistent vomiting 1. Weight loss or poor weight gain is common, and the condition is more prevalent in male infants and those with a family history of pyloric stenosis.

Importance of Prompt Recognition

Prompt recognition of pyloric stenosis is crucial, as the definitive treatment is surgical pyloromyotomy, which has excellent outcomes when performed after correcting fluid and electrolyte abnormalities 1. It is essential to consider pyloric stenosis in the differential diagnosis of infants presenting with vomiting, particularly if the vomiting is progressive and projectile, to ensure timely and effective treatment.

From the Research

Pyloric Stenosis Presentation

• Pyloric stenosis typically presents with nonbilious projectile emesis after feeds, which may result in hypokalemic, hypochloremic metabolic alkalosis 2.
• The classical symptom of projectile vomiting may be absent in some patients, and a pyloric tumor may not be palpated in others 3.
• Additional classical presenting findings include palpation of the pyloric tumor, described as olive-shaped, a visible gastric peristaltic wave after feeding, and hypochloremic, hypokalemic metabolic alkalosis 3.
• The clinical presentation of hypertrophic pyloric stenosis has not actually changed despite the easier accessibility of GI imaging studies, but the use of imaging and laboratory studies may have shortened the time for diagnosis and reduced the postoperative stay 3.
• Ultrasonography can be used to evaluate the pylorus and diagnose pyloric stenosis, with measurements including channel length and muscle thickness 4.
• A positive examination includes muscle thickness more than 4 mm and channel length more than 16 mm 4.
• The use of ultrasonography can help identify patients with a non-classical clinical presentation of pyloric stenosis 3.

Diagnosis and Treatment

• The diagnosis of pyloric stenosis can be made solely upon the surgeon's US evaluation, and surgeons who have undergone focused training to perform US for PS can diagnose the condition without confirmatory testing by a radiologist 4.
• Operative intervention is the treatment for pyloric stenosis, and it is imperative that patients are hydrated and serum electrolyte concentrations normalized before the induction of anesthesia 2.
• Laparoscopic pyloromyotomy is a safe and effective treatment for pyloric stenosis, and it may result in a small increase in mucosal perforation compared with open pyloromyotomy 5.
• Postoperative emesis is normal, and reassurance to parents is appropriate, as there is no significant long-term physiologic impairment from pyloric stenosis after successful surgical intervention 2.

Postoperative Changes

• After pyloromyotomy for hypertrophic pyloric stenosis, there is an early transient increase in muscle thickness within the first few postoperative days, followed by a slow decrease that reaches normal thickness by 5 months 6.
• The length of the pylorus gradually decreases after the operation, reaching 75% of the preoperative value by 5 months 6.
• The morphologic features of the pylorus after pyloromyotomy include a wedge shape at 3 days, a flat tire shape at 7 and 14 days, and an elongated ring shape at 5 months 6.