<unk>  as seen on ultrasound in a 6-week-old Diagnosis is via a careful history and physical examination, often supplemented by radiographic imaging studies.<unk>  should be suspected in any young infant with severe vomiting. On physical exam, palpation of the abdomen may reveal a mass in the epigastrium. This mass, which consists of the enlarged pylorus, is referred to as the 'olive', and is sometimes evident after the infant is given formula to drink. Rarely, there are peristaltic waves that may be felt or seen ( video on NEJM) due to the stomach trying to force its contents past the narrowed<unk>  outlet. Most cases of<unk>  are diagnosed/confirmed with ultrasound, if available, showing the thickened pylorus and non-passage of gastric contents into the proximal duodenum. Muscle wall thickness 3 millimeters (mm) or greater and<unk>  channel length of 15 mm or greater are considered abnormal in infants younger than 30 days. Gastric contents should not be seen passing through the pylorus because if it does,<unk>  should be excluded and other differential diagnoses such as pylorospasm should be considered. The positions of superior mesenteric artery and superior mesenteric vein should be noted because altered positions of these two vessels would be suggestive of intestinal malrotation instead of<unk> . Although the baby is exposed to radiation, an upper GI series (X-rays taken after the baby drinks a special contrast agent) can be diagnostic by showing the pylorus with elongated, narrow lumen and a dent in the duodenal bulb. This phenomenon caused "string sign" or the "railroad track/double track sign" on X-rays after contrast is given. Plain x-rays of the abdomen sometimes shows a dilated stomach. Although upper gastrointestinal endoscopy would demonstrate<unk>  obstruction, physicians would find it difficult to differentiate accurately between hypertrophic<unk>  and pylorospasm. Blood tests will reveal low blood levels of potassium and chloride in association with an increased blood pH and high blood bicarbonate level due to loss of stomach acid (which contains hydrochloric acid) from persistent vomiting. There will be exchange of extracellular potassium with intracellular hydrogen ions in an attempt to correct the pH imbalance. These findings can be seen with severe vomiting from any cause.
Pyloric stenosis
Gastroesophageal reflux disease
Retained antrum syndrome
Intussusception (medical disorder)
Gastric volvulus
Esophageal achalasia
Hiatal hernia
Atresia