Fiberoptic upper endoscopy is the diagnostic tool of choice for all children, including neonates. endoscopy provides direct visual observation of the lining of the esophagus, stomach, and proximal duodenum and also is a means for obtaining biopsy or culture material. Ultrasound may be performed to rule out gallstones, tumors, or mechanical obstruction. The fecal occult blood test may be performed to check for GI bleeding.