A 26-month-old girl presents with a lump in the upper abdomen, which her mother noticed for the first time today. She is asymptomatic. Her antenatal, birth, postnatal, medical, surgical, and family histories are unremarkable. All vaccinations are up-to-date. She is currently on a normal adult diet. A complete blood count, urinalysis, serum electrolytes, renal profile, and liver profile are all within normal parameters.