| Name of study | Utility |
| Complete blood count | Anemia and iron deficiency may be associated with obstruction, IBD, gastritis, and ulcer disease. |
| Elevated white blood cell count is associated with bacterial infections, appendicitis, and sepsis. | |
| Electrolytes, BUN, creatinine | Electrolyte abnormalities are associated with pyloric stenosis, adrenal insufficiency, and metabolic diseases. |
| Elevated BUN and creatinine are seen in kidney disease. | |
| Hepatic aminotransferases | Elevated AST, ALT, total bilirubin, and GGTP are seen in liver and gallbladder disease. |
| Amylase, lipase | Elevated in pancreatitis. |
| Plasma ammonia, urine-reducing substances | If an inborn error of metabolism is suspected. Ammonia is elevated in urea cycle disorders and organic acidemias. Non-glucose-reducing substances are usually present in the urine in galactosemia or hereditary fructose intolerance. |
| Plain radiograph of the abdomen | If intestinal obstruction is suspected. |
| Upper gastrointestinal series | If an anatomic abnormality of the upper gastrointestinal tract is suspected (eg, neonate with bilious vomiting). |
| CT of the head | If increased intracranial pressure is suspected (rule out mass). |
| Abdominal ultrasound | If pyloric stenosis or intussusception are suspected; also useful for evaluation of liver, gallbladder, kidneys, and pancreas. |
| Radionucleotide gastric emptying study | If gastroparesis is suspected. |
| Endoscopy | If peptic disease, eosinophilic esophagitis, IBD, or other causes of intestinal inflammation are suspected. |
