Congenital hypertrophic pyloric stenosis
LITFL overview: http://lifeinthefastlane.com/ccc/pyloric-stenosis/
Case study from LITFL with review questions: http://lifeinthefastlane.com/pediatric-perplexity-006/
PedEM Morsels on pyloric stenosis: http://pedemmorsels.com/pyloric-stenosis/