Pyloric stenosis
Pyloric stenosis is the narrowing of the lower portion of the stomach (pylorus) that leads into the small intestine. The muscles in this part of the stomach enlarge, narrowing the opening of the pylorus and preventing food from moving from the stomach to the intestine. This problem typically occurs in infants between 2 and 8 weeks of age and affects 1 out of every 500 to 1,000 live births.
Most babies with pyloric stenosis begin to vomit during the second to third week of life. Surgery is required to correct the problem and, once corrected, Pyloric stenosis almost never recurs.