What symptoms might indicate a baby is experiencing gastric outlet obstruction?

Forceful vomiting and signs of dehydration are key symptoms indicative of gastric outlet obstruction in infants. This condition occurs when there is a blockage at the pylorus, the opening from the stomach into the small intestine. As a result, food cannot pass through normally, leading to the characteristic projectile vomiting often observed in these cases.

In addition to vomiting, dehydration is a concerning complication that arises due to repeated emesis, as the infant may not be able to keep down liquids or nutrients. Signs of dehydration may include dry mucous membranes, decreased urine output, and increased lethargy. These symptoms occur because the infant's body loses more fluids than it takes in, which is exacerbated by the inability to effectively empty the stomach contents.

Other options describe symptoms that are less specific to gastric outlet obstruction. For instance, excessive drooling and lethargy may be seen in various conditions but do not directly point to this obstruction. Constipation and abdominal pain may indicate different gastrointestinal issues. Lethargy and decreased muscle tone are typically associated with generalized illness or metabolic disorders rather than a specific indication of gastric outlet obstruction.