How do you diagnose pyloric stenosis in an infant?

From the Guidelines

Pyloric stenosis in infants is best diagnosed through a combination of clinical evaluation and diagnostic imaging, with a thorough history and physical examination being the first step, followed by an ultrasound of the abdomen as the definitive diagnostic test. When evaluating an infant for pyloric stenosis, it is essential to start with a thorough clinical evaluation, including a detailed history and physical examination, as outlined in the study by 1. The history should focus on characteristic symptoms such as projectile vomiting after feeding, hunger after vomiting, and failure to gain weight. The physical examination may reveal a palpable olive-shaped mass in the right upper quadrant of the abdomen, visible peristaltic waves across the abdomen, and signs of dehydration. Some key points to consider in the diagnosis of pyloric stenosis include:

• Laboratory tests should include electrolytes to assess for hypochloremic, hypokalemic metabolic alkalosis, which commonly develops due to loss of gastric contents.
• The definitive diagnostic test is an ultrasound of the abdomen, which typically shows pyloric muscle thickness greater than 3-4 mm and pyloric channel length greater than 15-18 mm, as suggested by the study 1.
• If ultrasound is unavailable or results are equivocal, an upper GI contrast study can demonstrate the "string sign" or "shoulder sign" characteristic of pyloric stenosis. Before any diagnostic procedures, ensure the infant is adequately hydrated and electrolyte abnormalities are corrected. Once diagnosed, the treatment is surgical pyloromyotomy, which should be performed after fluid and electrolyte stabilization, as early diagnosis is crucial to prevent severe dehydration and metabolic disturbances in young infants, as highlighted in the study by 1.

From the Research

Diagnosis of Pyloric Stenosis in Infants

To diagnose pyloric stenosis in infants, the following methods can be used:

• Physical examination: A clinical diagnosis of pyloric stenosis can be made by history and physical examination alone, as seen in 73% of the infants in the study by 2.
• Ultrasound: Surgeon-performed ultrasonography can be used to diagnose pyloric stenosis, with measurements of channel length and muscle thickness being recorded at bedside, as demonstrated by 3.
• Radiology-performed ultrasound: This is a common method used to confirm the diagnosis of pyloric stenosis, with a sensitivity of 97% and specificity of 99% as shown in the study by 4.
• Upper gastrointestinal roentgenographic series and abdominal sonography: These imaging procedures can be used to confirm the diagnosis of hypertrophic pyloric stenosis, as noted in the study by 5.
• Endoscopy: In some cases, esophagastroduodenoscopy can be used to diagnose previously unsuspected infantile hypertrophic pyloric stenosis, as presented in the study by 6.

Diagnostic Criteria

The diagnostic criteria for pyloric stenosis include:

• Muscle thickness more than 4 mm and channel length more than 16 mm on ultrasound, as used in the study by 3.
• Palpation of a hypertrophied pylorus, which is diagnostic of hypertrophic pyloric stenosis, as stated in the study by 5.
• Measurements of the pyloric canal length, transverse pyloric diameter, and muscle wall thickness on ultrasound, as taken in the study by 4.