The crying infant with abdominal pain

What are your working differential diagnoses and what points in the history help differentiate them?

Having inserted a cannula you get the following results:

• venous blood gas: pH 7.33, pCO2 5.5, pO2 4.9, HCO3 19.3, BE -4.2, lactate 2.3, glucose 4.5
• sodium 134, potassium 4.3, urea 3.7, creatinine 18, corrected calcium 2.4, phosphate 1.5, alkaline phosphatase 206, alanine
• transaminase 21, bilirubin 5, albumin 39, c-reactive protein 11
• haemoglobin 11.3, white blood cells 10.5, neutrophils 3.9, platelets 342
• urine dip 1+ protein

The child has vomited again in the department. You have witnessed an episode whereby he is crying and unsettled and drawing up his legs, during which he looks very pale. You are concerned he may have intussusception.

What investigation(s) should you arrange next?

Abdominal ultrasound scan confirms intussusception. What will you do next for the patient and what will you explain to his parents about how he is going to be managed?