Discussion of Wilm's tumor
- Wilms tumor accounts for 87% of pediatric renal masses.
- Occurs in approximately 1:10,000 persons.
- Its peak incidence is at 3–4 years of age and 80% of patients present before 5 years of age.
- Bilateral in 4%–13% of children
- May be associated with congenital anomalies such as cryptorchidism (2.8% of cases), hemihypertrophy (2.5%), hypospadias (1.8%), and sporadic aniridia.
- Screening for Wilms tumor in patients with associated syndromes should begin at 6 months of age with initial computed tomography followed by serial ultrasonography every 3 months up to 7 years of age.
- After the age of 7 years, screening can be discontinued because the risk of developing Wilms tumor decreases significantly.
- Unilateral Wilms tumor is generally treated with nephrectomy followed by adjuvant chemotherapy.
- Local radiation therapy of the tumor bed is advocated in some cases, and complete abdominal irradiation can be used when there is gross tumor spillage at surgery or peritoneal tumor implantation.
- In children with bilateral Wilms tumor, preoperative chemotherapy is especially important because each kidney is staged separately, and complete resolution of disease in one kidney may allow surgery on the contralateral kidney with eventual cure.
- Cure rates are based on histologic findings and disease stage and have improved from 10% in the 1920s to over 90% today.
 Imaging Findings for Wilm's tumor
- Wilms tumor manifests as a solid intrarenal mass with a pseudocapsule and distortion of the renal parenchyma and collecting system.
- The tumor typically spreads by direct extension and displaces adjacent structures but does not typically encase or elevate the aorta; such encasement or elevation is a distinguishing characteristic of neuroblastoma.
- There may be vascular invasion of the renal vein and inferior vena cava with occasional extension into the right atrium.
- Metastases are most commonly found in the lungs (85% of cases), liver, and regional lymph nodes, and metastatic disease may also produce vascular invasion.
- At US, the mass has heterogeneous echogenicity, which represents hemorrhage, fat, necrosis, or calcification
- CT demonstrates the heterogeneous mass and nodal metastases, as well as areas of calcification and fat. Intravenous administration of contrast material is mandatory to detect nodal or hepatic metastases, tumor extension into the renal vein or inferior vena cava, contralateral synchronous tumor, and associated nephrogenic rests.
- At magnetic resonance imaging, Wilms tumor demonstrates low signal intensity on T1-weighted images and high signal intensity on T2-weighted images. MR
 See Also
 External Links
 References for Wilm's tumor
- Lisa H. Lowe, Bernardo H. Isuani, Richard M. Heller, Sharon M. Stein, Joyce E. Johnson, Oscar M. Navarro, and Marta Hernanz-Schulman. Pediatric Renal Masses: Wilms Tumor and Beyond. RadioGraphics 2000 20: 1585-1603.