Postoperative Changes of Ultrasonographic Pyloric Mass in Infantile Hypertrophic Pyloric Stenosis

ABSTRACT

BACKGROUND: Infantile hypertrophic pyloric stenosis (IHPS) is a well-recognized cause of vomiting in infancy and is easily cured by a Ramstedt pyloromyotomy. However there have been no reports on the postoperative appearance of a pyloric mass in Korea. METHODS: Twenty infants with IHPS and 20 control infants were studied ultrasonographically during the first year of life at a regular interval. According to examination intervals, the IHPS infants (n=20) were divided into three groups Group A (3 months, n=6), B (6 months, n=7), and C (12 months, n=7). At each examination, measurements were obtained concerning the length of the pyloric canal and the muscular thickness. RESULTS: The mean preoperative length of the pylorus of the IHPS group was 19.4+/-3.64 mm, ranging from 17 to 30 mm (control 7.73+/-2.67 mm) (p<0.0001). The mean pyloric muscle thickness of the IHPS group was 5.08+/-0.67 mm, ranging from 3.5 to 6 mm (control 2.37+/-0.58 mm) (p<0.0001). The preoperative and postoperative measurements were subsequently compared. Postoperatively, the length of the pylorus averaged 22.0+/-2.66 mm, and the muscular thickness was 6.53+/-1.68 mm (p<0.0001). The reduction rates in pyloric length were 23.5%, 46.3%, and 53.4% for the respective groups. Also, the muscle-thickness reduction rates were 31.8%, 48.9%, and 57.8% respectively. At 6 months after the operation, the pyloric muscular thickness was in the normal control range, and the pyloric length was reduced to the normal range after 12 months. CONCLUSIONS: This prospective study suggests that the pyloric mass undergoes a rapid reduction in size in the first 6 months, followed by a more gradual reduction to a normal value by 12 months after a pyloromyotomy.