The ultrasonic diagnosis of infantile hypertrophic pyloric stenosis: technique and accuracy.

The role of ultrasound for the diagnosis of pyloric stenosis has yet to be definitely established. We have carried out 147 ultrasound examinations of 142 infants (99 male and 43 female) with a history of projectile vomiting or the possibility of a pyloric mass. Measurements of the pyloric canal length, transverse pyloric diameter and muscle wall thickness were taken from a longitudinal view of the pylorus and related to previously described control data. The accuracy of the ultrasound examination was related to the finally established diagnosis. The results obtained revealed a sensitivity of 97% and specificity of 99% with positive predictive value of 99%. The three diagnostic errors (1 false positive and 2 false negative) occurred during the 'learning curve' of the radiologists and were the 15th, 29th and 35th cases examined, indicating that almost a 100% accuracy can potentially be achieved. This study confirms that ultrasound examination is the first line of investigation in a child in whom the clinical diagnosis of hypertrophic pyloric stenosis is uncertain and indicates that unnecessary surgery can thereby be prevented.