Significance of ultrasound for the diagnosis of hypertrophic pyloric stenosis

The sonographic features of hypertrophic pyloric stenosis (HPS) were evaluated in a 5-year prospective study (1981-1985) at the University Clinic of Pediatric Surgery in Mainz. In 37 cases real-time ultrasound was performed preoperatively to measure muscle thickness, diameter, and length of the pylorus; the recorded values were compared with those of a control group. Muscular wall thickness proved to be the most reliable parameter, while pyloric canal length was the most difficult measurement to obtain. Diameter alone was not adequate to establish the sonographic diagnosis, which depends on the individually and functionally different luminal width and submucosal thickness. Significant sonographic criteria for the diagnosis of HPS are a muscle thickness of 5 mm or more and a diameter of 15 mm or more. These data are confirmed by intraoperative measurements. Indirect signs of HPS are a lack of passage through the narrowed pyloric canal, gastric distension combined with unproductive contractions and, less commonly, gastroesophageal reflux. Although history and clinical examination are the main diagnostic means, ultrasound should be the initial imaging procedure if the clinical diagnosis is doubtful.