Ultrasonography with the high-frequency linear transducer is the modality of choice for detection of Hypertrophic pyloric stenosis (HPS). It allows direct observation of the pyloric canal, usually located slightly medial and posterior to the gallbladder.

The diagnostic criteria for measurement of HPS are the thickness of the muscular layer >3 mm and elongation of the pyloric canal >12 mm.

Upper gastrointestinal series, however, is not the modality of choice for evaluation of HPS, but can exclude other causes of upper gastrointestinal obstruction.

Case contributed by: Dr. Hidayatullah Hamidi, Dr. Jalil Wardak and Dr. Yalda Obaidi.