Abdominal pain is one of the commonest presentations to the paediatric emergency department. Many children are brought to the PED due to concerns about surgical intra-abdominal pathology such as appendicitis. Mesenteric adenitis is commonly attributed as a cause of the patient's pain but is done so without confirmatory imaging findings and as a diagnosis of exclusion.

There is a paucity of evidence pertaining to the sonographic findings of mesenteric adenitis.

The investigators aim to categorise the normal appearances using POCUS in patients presenting to the paediatric emergency department without any abdominal or infectious complaint, in order to describe the range of normal lymph node numbers and size present on scan. By defining what's normal, the ultimate aim will be to use POCUS to actively identify abnormalities that diagnose mesenteric adenitis.

Inclusion Criteria:

- patients aged 2 - 16 years who present to the paediatric emergency department with the following conditions: head injury, facial injury, neck injury, upper and lower limb injury.

Exclusion Criteria:

• any child who has had symptoms of vomiting (including those with concurrent head injury), diarrhoea, abdominal pain, anorexia, temperature or active evidence of urinary or respiratory tract infection within the last four weeks.

Any patient who has undergone abdominal surgery in the last 6 months.

Patients who present to the paediatric emergency department with the following conditions: head injury, facial injury, neck injury, upper and lower limb injury.

This will take place across 5 hospital sites in the UK, USA and Australia