Gastric contents should not be seen passing through the pylorus because if it does, pyloric stenosis 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 pyloric stenosis.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 pyloric obstruction, physicians would find it difficult to differentiate accurately between hypertrophic pyloric stenosis 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. Treatment
Infantile pyloric stenosis is typically managed with surgery; very few cases are mild enough to be treated medically. The danger of pyloric stenosis comes from the dehydration and electrolyte disturbance rather than the underlying problem itself.
The vomited material does not contain bile because the pyloric obstruction prevents entry of duodenal contents (containing bile) into the stomach. The chloride loss results in a low blood chloride level which impairs the kidneys ability to excrete bicarbonate. This is the factor that prevents correction of the alkalosis leading to metabolic alkalosis.A secondary hyperaldosteronism develops due to the decreased blood volume. The high aldosterone levels causes the kidneys to avidly retain Na+ (to correct the intravascular volume depletion), and excrete increased amounts of K+ into the urine (resulting in a low blood level of potassium).The bodys compensatory response to the metabolic alkalosis is hypoventilation resulting in an elevated arterial pCO2. Diagnosis
Diagnosis is via a careful history and physical examination, often supplemented by radiographic imaging studies. Pyloric stenosis 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 pyloric outlet.Most cases of pyloric stenosis 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 pyloric channel length of 15 mm or greater are considered abnormal in infants younger than 30 days.