Which of the following is a common symptom in a child diagnosed with Wilms tumor?

In children diagnosed with Wilms tumor, a unilateral abdominal mass is a classic presenting symptom. This type of tumor, also known as nephroblastoma, typically arises in one kidney and can lead to significant abdominal enlargement as it grows. Parents or caregivers often notice a firm, smooth mass in the abdomen during routine activities or examinations, which is usually not tender.

Wilms tumor may occasionally be associated with other symptoms, but the presence of a unilateral abdominal mass is the most characteristic and distinguishing feature of this pediatric renal tumor. By the time a diagnosis is made, the mass may be quite large, although the child may not exhibit other overt symptoms initially.