Congenital hypertrophic pyloric stenosis is a common condition in the neonatal period. One of the most reliable diagnoses is based on palpation of the pyloric mass. Examination related to pyloric mass: Abdominal examination: to be placed in a comfortable position, either lying on the mother’s lap, with the abdomen fully exposed and observed in bright light while feeding sugar water, the gastric pattern and peristaltic waves can be seen, with the waveform appearing under the left costal margin, slowly crossing the upper abdomen in 1 or 2 waves forward and finally disappearing on the right side above the umbilicus. The examiner is located on the left side of the infant and must be gentle. The left hand is placed at the outer edge of the rectus abdominis muscle under the right costal margin, and the index and ring fingers are used to press the rectus abdominis muscle, and the end of the middle finger is used to gently press deeper to palpate an olive-shaped, smooth and hard pyloric mass, 1 to 2 cm in size. It is easily palpable when the stomach is empty after vomiting and the abdominal muscles are temporarily relaxed. Occasionally, the caudal lobe of the liver or the right kidney is mistaken for a pyloric mass. However, when the abdominal muscles are not relaxed or when the stomach is dilated, the mass may not be found, so it can be examined after the gastric tube is emptied and sugar water is fed while sucking, and it should be examined repeatedly with patience. Laboratory tests may reveal that infants with clinical water loss have varying degrees of hypochloremic alkalosis, elevated blood Pco2, elevated pH and low serum chloride. It is also important to recognize that metabolic alkalosis is often accompanied by hypokalemia, the mechanism of which is not clear. In addition to the small amount of potassium lost with gastric juice, potassium ions move intracellularly during alkalosis, causing high intracellular potassium and low extracellular potassium, and increased potassium excretion from the epithelial cells of the distal tubule of the kidney, resulting in lower blood potassium. Gastric ultrasonography: The biggest advantage of gastric ultrasonography is that the sound beam can penetrate the stomach wall, thus showing the hierarchical structure of the stomach wall. As a non-invasive diagnostic method, it can provide clinical information on the location, size and morphology of cancer in the stomach wall, and sometimes can estimate the extent of lesion invasion in the stomach wall. It can also detect early gastric cancer, especially to understand the metastasis of perigastric organs, make up for the shortcomings of gastroscopy and X-ray, and provide a basis for clinical selection of treatment plan. At present, the detection rate of transabdominal ultrasonography for gastric cancer is low, and the sensitivity for early gastric cancer is only 15%, so it is not used as a screening tool for gastric cancer. With the clinical application of ultrasound endoscopy, the clinical value of gastric ultrasound has been further improved.