Partial nephrectomy remains controversial and is not recommended except for children with bilateral tumors, children with a solitary kidney, or rare cases of horseshoe kidney. However, partial nephrectomy has been suggested for Wilms tumor in infants with Denys-Drash or Frasier syndrome in order to delay the need for dialysis.; [Level of evidence: 3iiB] Also, some children who are predisposed to bilateral tumors who have very small tumors detected by ultrasound screening may be considered for partial nephrectomy to preserve renal tissue. In North America, renal-sparing partial nephrectomy of unilateral Wilms tumor following administration of chemotherapy to shrink the tumor mass is considered investigational.[14,15]
Hilar, periaortic, iliac, and celiac lymph node sampling is mandatory even if the nodes appear normal. Furthermore, any suspicious node basin should be sampled. Margins of resection, residual tumor, and any suspicious node basins should be marked with titanium clips. Resection of contiguous organs is rarely indicated and there is an increased incidence of complications occurring in more extensive resections involving removal of additional organs beyond the diaphragm and adrenal gland. This has led to the recommendation in current COG protocols that these patients should be considered for initial biopsy, neoadjuvant chemotherapy, and then secondary resection. Pathologically, Wilms tumor rarely invades adjacent organs. Primary resection of liver metastasis is not recommended. Wilms tumor arising in a horseshoe kidney is rare and accurate preoperative diagnosis is important in planning the operative approach. Primary resection is possible in most cases. Inoperable cases can usually be resected after chemotherapy.
Preoperative chemotherapy prior to nephrectomy is indicated in the following situations:[10,16,16,19,20,21,22]
- Metachronous bilateral Wilms tumor.
- Wilms tumor in a solitary kidney.
- Extension of tumor thrombus above the level of the hepatic veins.
- Tumor involves contiguous structures whereby the only means of removing the kidney tumor requires removal of the other structures (e.g., spleen, pancreas, colon but excluding the adrenal gland).
- Pulmonary compromise due to extensive pulmonary metastases.
- Retroperitoneal rupture with free fluid contained by Gerota fascia.
Patients with massive, nonresectable unilateral tumors, bilateral tumors, or venacaval tumor thrombus extending above the hepatic veins are candidates for preoperative chemotherapy because of the risk of initial surgical resection.[10,16,19,20] Preoperative chemotherapy should follow a biopsy, except in the setting of bilateral disease (COG-AREN0534). The biopsy may be performed percutaneously through a flank approach.[23,24,25,26,27,28] Preoperative chemotherapy should include doxorubicin in addition to vincristine and dactinomycin unless there is anaplastic histology present, which then includes treatment with other agents. The chemotherapy generally makes tumor removal easier because of the decreased size and vascular supply of the tumor and may reduce the frequency of surgical complications.[16,19,28,29,30] Postoperative radiation therapy to the tumor bed is required when a biopsy is performed or in the setting of local tumor stage III.