Further history:
Kaji, aged 6 months, is Narindra’s brother, who presents two years later because of vomiting and 6 hours of intermittent screaming. He had been previously healthy. The vomiting was profuse but not projectile.
On examination Kaji is pale and lying quietly.

His vital signs are:
Pulse 150
Respiration rate 34
Temperature 37.0 C
BP 65/40

Kaji is observed to become distressed with sudden screaming and drawing up of his legs as though in pain. A firm mass is palpable just above and to the right of the umbilicus. A small amount of normal stool was passed into his nappy.

Which of the following statements would you consider to be correct?