A 3 month old boy with vomiting, intermittent crying, and lethargy

The mother of a 3 month old boy brought her child to the emergency department at midday. Since that morning he had been having intermittent episodes of severe crying, which his mother said “wasn’t like him at all.” He occasionally brought his legs up to his chest and his mother thought that he was in considerable pain. The child had vomited twice that morning and become more lethargic. He was now refusing to breast feed. His mother had changed only one wet nappy that morning and a soiled nappy overnight. She had not seen any blood in the stool and the child had not had a fever. He had been born by uncomplicated vaginal delivery at 36 weeks. Apart from mild hyperemesis during the first trimester, the mother’s obstetric history was unremarkable. There were no concerns during the neonatal period. Before he became unwell, the boy had been having frequent wet nappies, opening his bowels regularly, and breast feeding well. On examination, he was initially quiet. He had mottled skin and dry mucous membranes. He then had a severe episode of crying, and was noted to draw his legs up to his chest. His vital signs were pulse 180 beats/min, respiratory rate 60 breaths/min, and temperature 37.5°C. His abdomen was distended and diffusely tender. No abdominal mass was palpable and bowel sounds were normal. Blood tests were unremarkable. An urgent ultrasound was performed for further assessment (fig 1⇓). Fig 1 Axial ultrasound of the abdomen using a high frequency ultrasound probe with the probe held in the upper part of the abdomen.