The survival metrics of children with Wilms tumor appear to be improving over time. According to the SEER registry, the relative 5-year survival rate for children younger than the age of 15 years has improved from 73.1% in 1975 to 93.6% in 2002 (2). This improvement in the long-term survival of children with Wilms tumor is a testament to the systematic approach from which multimodal therapy has evolved. Despite the advances in chemotherapy protocols and radiation techniques, a high-quality surgical operation remains paramount in the treatment of Wilms tumor. Primary radical nephrectomy is the procedure of choice for the majority of patients with unilateral Wilms tumor diagnosed in North America. Renalsparing surgery has been traditionally used in patients with bilateral Wilms tumors. However, the Children’s Oncology Group is now studying the role of renal-sparing surgery for select patients with unilateral tumors. Patients eligible for renal-sparing surgery on this protocol include those with a solitary kidney, a predisposition syndrome where tumors are found at a smaller size, and patients with an increased risk for developing renal failure (14,15). Several small single institution reports have documented the feasibility of partial nephrectomy in select cases of “low-risk” unilateral tumors, where nephron preservation is not imperative and where the risk of metachronous tumor formation is low (16). With respect to laparoscopy, there are reports in children with unilateral nonmetastatic Wilms tumor who received preoperative chemotherapy (17). However, the role of laparoscopy prior to chemotherapy may be limited because of large tumor size and risk of intraoperative spillage.

Tumor histology and stage are the most important determinants of prognosis in patients with Wilms tumor. Tumor grade, particularly the presence of anaplasia, is the most important prognostic factor and portends a poorer prognosis compared to favorable histology. The staging system used by the Children’s Oncology Group is presented in Table 85.1 and is based on various intraoperative and pathologic findings.

The International Society of Pediatric Oncology (SIOP) advocates preoperative chemotherapy for all patients with Wilms tumor regardless of the extent of disease (18). Preoperative treatment can produce dramatic reduction in the size of the primary tumor, facilitating surgical excision. The SIOP trials have demonstrated that the incidence of tumor rupture is lower after preoperative therapy. There is no survival advantage over a primary surgical approach. The Children’s Oncology Group (COG) recommends preoperative chemotherapy in children with bilateral tumors, tumors inoperable at surgical exploration, or IVC extension above the hepatic veins. All other patients are recommended to undergo primary excision of the tumor. This allows precise staging of patients with modulation of treatment for each individual, thereby decreasing the intensity of treatment when possible while maintaining excellent overall survival.

The recommended surgical approach for Wilms tumor is through a transperitoneal transabdominal incision. An extraperitoneal flank incision should be avoided because it does not allow for proper staging. A generous transverse abdominal incision allows for inspection and exploration of the abdominal cavity. The patient is placed in a supine position with mild flexion of the lumbar spine to facilitate the exposure of retroperitoneal structures. The incision is made approximately two fingerbreadths above the umbilicus beginning in the midaxillary line on the side of the neoplasm. The extent to which the incision is extended across the midline will vary with the size of the tumor and amount of exposure needed. The incision may be extended into a thoracoabdominal approach by continuing through the bed of the 9th or 10th rib, if necessary. The muscle layers are divided sequentially to facilitate exposure. The peritoneal space should be opened carefully.
The tumor may compress the colon and/or small bowel against the anterior abdominal wall, inadvertently resulting in enterotomy. A thorough exploration of the abdomen is performed. The peritoneal cavity is assessed for evidence of preoperative tumor rupture and peritoneal implants. The liver is carefully examined, as liver metastases may not be identified on preoperative imaging studies. An assessment of tumor extent is performed next, including palpation of the IVC and assessment of regional lymphadenopathy, perinephric extension, and tumor mobility. Formal exploration of the contralateral kidney is not needed if preoperative imaging does not demonstrate bilateral lesions (19).