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.
Blood findings
The blood film can point towards vitamin deficiency:

Decreased red blood cell (RBC) count and hemoglobin levels
Increased mean corpuscular volume (MCV, >100 fL) and mean corpuscular hemoglobin (MCH)
Normal mean corpuscular hemoglobin concentration (MCHC, 32–36 g/dL)
Decreased reticulocyte count due to destruction of fragile and abnormal megaloblastic erythroid precursor. The platelet count may be reduced. Neutrophil granulocytes may show multisegmented nuclei ("senile neutrophil"). This is thought to be due to decreased production and a compensatory prolonged lifespan for circulating neutrophils, which increase numbers of nuclear segments with age. Anisocytosis (increased variation in RBC size) and poikilocytosis (abnormally shaped RBCs). Macrocytes (larger than normal RBCs) are present. Ovalocytes (oval-shaped RBCs) are present. Howell-Jolly bodies (chromosomal remnant) also present.Blood chemistries will also show:

An increased lactic acid dehydrogenase (LDH) level. The isozyme is LDH-2 which is typical of the serum and hematopoietic cells. Increased homocysteine and methylmalonic acid in Vitamin B12 deficiency
Increased homocysteine in folate deficiencyNormal levels of both methylmalonic acid and total homocysteine rule out clinically significant cobalamin deficiency with virtual certainty.Bone marrow (not normally checked in a patient suspected of megaloblastic anemia) shows megaloblastic hyperplasia. See also
List of circulatory system conditions
List of hematologic conditions

References
External links

GeneReview/NCBI/NIH/UW entry on Thiamine-Responsive Megaloblastic Anemia Syndrome
Rare Anemias Foundation