RADIOLOGY: GASTROINTESTINAL: GI: Case# 33634: PYLORIC STENOSIS. 6 week old infant with recurrent non-bilious vomiting. Ultrasound of the abdomen was performed utilizing a linear 5 MHz transducer. This revealed a distended stomach with a thickened pylorus. The muscle thickness was greater than 3.5 mm and a channel length greater than 17 mm. The patient was given pedialyte by bottle and no fluid was seen to pass through the gastric antrum. Findings are compatible with hypertrophic pyloric stenosis. Hypertrophic pyloric stenosis is seen in infants from approximately two to eight weeks of age. It is more common in first born boys than girls. Incidences are approximately 3/1000 children. The classic presentation is non-bilious vomiting. Physical exam frequently reveals an olive mass. When the physical findings are non-diagnostic, ultrasound can be performed to evaluate for pyloric muscle thickness and pyloric canal length.