Test 11

Wilms tumour, also known as nephroblastoma, is the most common malignant renal tumour in children, occurring typically before the age of 5 years. Ultrasound is the initial imaging modality of choice and often demonstrates a large retroperitoneal mass arising from the kidney with a surrounding ‘claw’ of normal renal parenchyma. This is known as the ‘claw sign’ which is a useful radiological sign that can be used to determine if a mass arises from solid parenchyma (intrinsic mass) or adjacent to it (extrinsic mass), distorting the parenchyma on ultrasound, CT and MRI. The renal vein and inferior vena cava should be assessed for tumour thrombus, which is seen in approximately 10% of cases. CT of the thorax, abdomen, and pelvis is performed to assess for metastases, which most commonly occur to the lungs: 10–20% of cases have pulmonary metastases at the time of diagnosis.