**Core Concept**
Gross hematuria in a child without urinary symptoms, pyuria, or infection, with normal serum C3 and sterile urine, raises suspicion for a glomerular disease or neoplasm. Among pediatric causes, malignancy such as Wilm’s tumor can present with painless, recurrent gross hematuria, especially in young males.

**Why the Correct Answer is Right**
Wilm’s tumor is the most common renal malignancy in children and can present with painless gross hematuria, often without fever, dysuria, or pyuria. It may be associated with normal C3 levels and sterile urine, as it does not typically involve bacterial infection or immune-mediated glomerulonephritis. The absence of pus cells and pyuria rules out urinary tract infection or post-streptococcal glomerulonephritis. In children under 5 years, especially males, persistent gross hematuria without infection should prompt immediate investigation for renal tumor.

**Why Each Wrong Option is Incorrect**
Option B: IgA nephropathy typically presents with episodic hematuria after upper respiratory infections, often with microscopic hematuria, and may show elevated serum C3 in early stages — not consistent with normal C3 here.
Option C: Post-streptococcal glomerulonephritis presents with acute onset of hematuria, edema, hypertension, and **low serum C3** — which is absent in this case.
Option D: Urinary tract infection is ruled out by sterile urine and absence of pyuria or symptoms like dysuria or fever.

**Clinical Pearl / High-Yield Fact**
In children under 5 years with painless, recurrent gross hematuria and normal C3, Wilm’s tumor should be considered first — especially in males — and imaging or renal ultrasound should be performed immediately.

✓ Correct Answer: A. Wilm's tumour