Ella, a 9-month-old female, is brought to the emergency room by her parents due to episodes of crying and pulling her legs up to her chest that have been occurring every 15–20 minutes over the past day. During these episodes, Ella appears pale and irritable. The parents report that she has had non-bilious vomiting initially, but it became green and bilious as the day progressed. On examination, Ella appears lethargic between crying episodes, her abdomen is distended, and a palpable “sausage-shaped mass” is noted in the right upper quadrant. Ultrasound confirmed the diagnosis which revealed a characteristic ‘target lesion’ and the patient is successfully treated with pneumatic enema. Which of the following is the hallmark symptom of this disease in children?
