Risk based therapy is a key element to successful treatment of a child with a renal tumor.1 The surgeon plays an important role in accurately staging the disease which is essential to determine the requirement for and appropriate chemotherapy and radiation therapy. Staging (Table 1) is comprised of a combination of several factors for both local and metastatic disease. Adequate evaluation of local intraabdominal disease includes documentation of preoperative rupture and/or intraoperative spill, determination of resectability, and assessing for the presence of contiguous tumor extension into adjacent structures or organs.

Critical Elements:

Intraoperative assessment of resectability, including determination of preoperative rupture, contiguous extension, sampling of peritoneal fluid, and clinical staging.

Radical nephroureterectomy without capsule violation or rupture (R0 resection).

Proximal vascular ligation with isolation and division of the renal vessels.

Palpation and distal resection of ureter.

Retroperitoneal lymph node sampling of basins expected anatomically to drain the kidney.

1. Intraoperative assessment of resectability, including determination of preoperative rupture, contiguous extension, sampling of peritoneal fluid, and clinical staging.

Recommendation: A patient with a unilateral renal tumor of childhood should have an upfront radical nephroureterectomy. Preoperative planning including review of imaging and intraoperative clinical assessment should thus be done with the focus of reasons to forgo resection.

Type of Data: prospective randomized controlled studies, retrospective series, and case control studies.

Strength of Recommendation: Strong recommendation; high quality evidence

Rationale: Several large prospective cooperative group trials created treatment protocols that have improved outcomes for children with renal tumors. These include the National Wilms Tumor Study Group (NWTSG), Children's Oncology Group (COG), International Society of Paediatric Oncology (SIOP) and the United Kingdom Children's Cancer Study (UKCCSG).2, 3, 4, 5, 6, 7 Upfront nephrectomy is recommended as the first step in treatment of Wilms tumor by the COG and its predecessor organization the NWTSG.1 Primary nephrectomy with lymph node sampling accurately determines the stage and allows for assessment of the pathologic and genetic characteristics of the tumor. Failure to properly assess intraoperative resectability or to perform the operation correctly can result in under or over staging the tumor, resulting in inappropriate therapy.8,9 Although most children with renal tumors have an event free survival of over 85 %, for those who relapse, both event free and overall survival decline to less than 40 %.10,11

Renal tumors are given both a local stage and an overall disease stage. Local stage ranges from I-III and overall disease stage ranges from I-V. Pulmonary and hepatic locations are the most common sites of stage IV distant metastatic disease although osseous metastasis can occur in clear cell sarcoma of the kidney (CCSK) and brain metastasis occur in both CCSK and rhabdoid tumors. Direct extrarenal extension of tumor can be either stage II if it is completely resected with negative pathologic margins or stage III if the margins are involved. Involvement of abdominal lymph nodes also results in stage III disease as does tumor spill or biopsy during resection. Local stage determines whether abdominal radiotherapy is administered for most tumor types and the overall stage determines the intensity and duration of the chemotherapy. Children with pulmonary metastasis may receive pulmonary radiotherapy based on the response of their pulmonary disease.

Cross-sectional imaging should be reviewed closely prior to surgery to assess tumor size, location, relationship to surrounding structures, and the presence or absence of metastatic disease. Improvements in preoperative imaging modalities, including the use of thin-slice computed tomography (CT) and magnetic resonance imaging (MRI), have shifted the timing of diagnosis of extrarenal and metastatic disease from the intraoperative to the preoperative time period.12,13 Nevertheless, it is incumbent upon the surgeon to routinely and systematically evaluate the abdomen for the presence of metastatic foci and extrarenal disease, and to make an accurate intraoperative determination regarding the feasibility of complete resection of the primary tumor.

A misconception is that cross-sectional imaging can determine both the local and overall disease stage, node positivity, and resectability. Several studies have shown that the sensitivity and specifically of cross-sectional imaging to determine resectability, rupture and nodal status is low.14,15 Preoperative rupture or intraoperative spill must be carefully documented by the surgeon at the time of resection for accurate staging and treatment assignments.

Although the current treatment approach is generally to pursue immediate nephrectomy, there are occasional patients for whom preoperative chemotherapy is warranted. Preoperative chemotherapy should be considered in the following situations: (a) extension of tumor thrombus at or above the level of the hepatic vein confluence; (b) tumor involvement of contiguous structures whereby the only means of complete resection would require removal of the other structures (e.g., spleen, pancreas, colon but excluding the adrenal gland and small portion of the diaphragm); (c) it is the surgeon's judgment that nephrectomy would result in significant or unnecessary morbidity/mortality, diffuse tumor spill, or residual tumor; (d) pulmonary compromise due to extensive pulmonary metastases, and (e) the presence of bilateral renal masses.

Most renal tumors in children are large (i.e., frequently >12 cm), therefore an open transperitoneal approach is recommended to achieve safe and complete assessment and resection.16,17 Minimally invasive approaches have been reported in small series, without direct comparison of tumor resectability, spill, or margin status compared to the open surgical approach. As such, open surgery remains the gold standard operative technique. Adequate exposure allows for full abdominal exploration with assessment of the presence and character of peritoneal fluid, tumor implants, and careful mobilization of the tumor, including freeing of intraperitoneal attachments and retroperitoneal tissue planes without rupture or violation of the capsule. Renal tumors can extend into the renal vein, inferior vena cava, and rarely into the right atrium, therefore particular attention including palpation of the renal vein and ureter is important to assess for tumor extension into these structures.18