Rahim, a 3-year old boy, presented with a gradually enlarging abdominal mass in his left side for 2 months. He also experienced abdominal pain and blood in his urine. On examination, a 10x8cm firm mass was found in his left lumbar region. Based on his history and examination, the provisional diagnosis was a left renal mass that may be nephroblastoma. Differential diagnoses included neuroblastoma and hydronephrosis. Investigations such as ultrasound, CT scan, MRI, and urine tests were recommended to confirm the diagnosis and assess for metastasis. The treatment plan would depend on whether the tumor was resectable or inoperable, and if there was metastasis present.