Increased metabolism increases oxygen demand which increases respiratory rate and increases fluid loss so child gets easily dehydrated. With babies, GI problems are also related to air swallowing which increases danger of aspiration. Child needs to be burped frequently to remove swallowed air. Then place on right side or prone. As they mature, it tightens and regurgitation decreases.
Abdominal protrusion is normal.
If concave, needs investigation. There is increased risk of drug toxicity because kidneys don't excrete toxins rapidly. Child has smaller absolute urine volume but larger proportionate urine output per kg body weight.