📊 Epidemiology by Age
• Neonates: hydronephrosis (most common), multicystic dysplastic kidney, neuroblastoma, mesoblastic nephroma
• Infants/toddlers: neuroblastoma, Wilms tumor, hepatoblastoma
• Older children: Wilms tumor, lymphoma, ovarian masses (adolescents)
🩺 Key Distinguishing Features
• Wilms tumor: smooth, non-tender, rarely crosses midline, hematuria possible, associated with aniridia/hemihypertrophy (WAGR syndrome)
• Neuroblastoma: firm, irregular, crosses midline, calcifications, opsoclonus-myoclonus, hypertension (catecholamines)
• Hydronephrosis: fluctuant, may be bilateral, history of UTIs
⚠️ Red Flags (Malignancy)
• Non-tender, firm, irregular mass
• Crosses midline (neuroblastoma)
• Constitutional symptoms: fever, weight loss, night sweats
• Left-sided varicocele (Wilms tumor with renal vein invasion)
• Elevated LDH, uric acid (lymphoma), VMA/HVA (neuroblastoma)
📋 Diagnostic Algorithm
• Ultrasound: first-line (cystic vs solid, organ of origin)
• CT/MRI: staging, vascular involvement
• CBC, LDH, uric acid, renal function, urine catecholamines (VMA/HVA)
• Biopsy for tissue diagnosis
📌 Decision strategy: Ultrasound determines cystic vs solid and organ of origin. Hydronephrosis most common in neonates. Wilms = smooth, neuroblastoma = irregular/crosses midline. Always consider pregnancy in adolescent females with pelvic mass.