Surgery is the preferred primary treatment for 90-95% of Wilms tumor cases in North America. Initial nephrectomy is usually feasible despite the presence of a large tumor mass.
The surgical goals are to:
- Assess and stage intra-abdominal disease
- Completely resect tumor without rupture or spillage
Preliminary surgery helps to determine subsequent chemotherapy and radiotherapy treatment plan.
The standard approach regardless of the involvement of the tumor is to make a transverse-transperitoneal incision with division of the ipsilateral rectus muscle across the midline. This incision can be extended as necessary for larger tumors and allows maximal exposure of the abdominal region for adequate surgical exploration.
Transperitoneal approach also allows early clamping of blood vessels and examination of the opposite kidney, which if involved requires different surgical management.
Upon entering the peritoneal cavity, the surgeon should:
1. Assess tumor extent.
2. Palpate liver, periaortic area and vena cava.
- During surgery, the inferior vena cava and renal vein should be carefully handled to avoid dislodging possible tumor thrombus.
- If dislodgment happens, tumor can potentially embolize to the lungs
- IVC involvement should be detected pre-operatively by ultrasound or CT. Consideration should be given to pre-operative chemotherapy to shrink the intravascular tumor and cause the tumor to fibrose, decreasing the risk of tumor fragmentation which can lead to lethal pulmonary embolization.
3. Biopsy suspicious nodules
4. Explore contralateral kidney
5. Mobilize ipsilateral colon
6. Open Gerota’s fascia and palpate anterior and posterior surfaces
7. Inspect hilar and regional lymph nodes.
- Biopsy lymph nodes in renal hilum and sample suspicious nodes along inferior vena cava and aorta.
- Routine lymph node sampling from the iliac, para-aortic and celiac areas must be done for accurate staging.
- Involved or suspicious lymph nodes should be excised. Formal lymph node dissection is not recommended.
- Titanium clips should be placed where the lymph nodes were biopsied to guide subsequent radiotherapy
- Failure to sample lymph nodes is an adverse prognostic feature.
8. Perform a nephrectomy for unilateral disease but biopsy for bilateral disease.
- Radical nephrectomy is the preferred procedure.
- Depending on the extent of the disease, other types of nephrectomy can be used in situations such as bilateral Wilms tumor.
- If complete resection is not possible, titanium clips should be placed in areas of residual tumor to guide postoperative radiotherapy.
The surgeon should assign a "local-regional stage" to the tumor based solely on the operative findings.
- Presence of distant metastases does not influence the "local" surgical staging (patient would be evaluated as "surgical stage III" if there were obviously positive lymph nodes even if it were known that pulmonary metastases were also present).
- Presence or absence of disease in hilar and regional lymph nodes is an extremely important factor in accurate staging.
Bilateral Wilms Tumor (Stage V)
Increased incidence of congenital abnormalities.
Tumors tend to have a more indolent clinical course. Favorable histology disease is most common.
Usually there is one kidney with virtually no salvageable renal substance while the opposite side has multiple cortical lesions. Most patients present with synchronous disease. Metachronous disease presentations have an ominous prognosis.
The aim of treatment is maximal conservation of uninvolved renal parenchyma through preoperative chemotherapy. The one large tumor usually requires radical nephrectomy. Pre-operative chemotherapy is used to shrink the smaller tumors maximally so that at second look surgery, residual disease can be "picked out" from the remaining kidney.
Renal impairment due to more than one half of renal parenchyma is prevalent. The goal of treatment is to gain local tumor control and preserve renal function.
Tumor Spillage or Soiling
Contamination of the peritoneum impacts treatment planning. The peritoneum is considered "soiled" if there has been
A pre-chemotherapy biopsy
- Pre-operative incisional or percutaneous needle biopsy using either the anterior or posterior approach are considered "local spillage".
- Incisional biopsy during surgery prior to nephrectomy is considered local spill unless in the surgeon's judgment, the whole peritoneal cavity has been soiled in the process.
"Spillage" of the tumor
- Spillage refers to transgression of the tumor capsule or its extensions during operative removal whether accidental, unavoidable or by design.
- Tumors adherent to adjacent structures and removed en bloc entail no tumor spill.
- Those that are removed as separate specimens (neoplastic tissue is cut across in the process), are considered to be spilled (local or diffuse).
"Rupture" of the tumor
- Rupture refers to either the spontaneous or post-traumatic rupture of the tumor preoperatively resulting in dissemination of tumor cells throughout the peritoneal cavity.
- If tumor ruptures preoperatively, the patient is classified as stage III, and whole abdominal radiation therapy is recommended.
Bloody peritoneal fluid
- Considered a sign of major soilage, whether or not gross or microscopic tumor is identified in the fluid.
- Separate, distinct nodules of tumor on the peritoneal or serosal surfaces, at a distance from the primary neoplasm "satellite implants" are considered a sign of major soilage.
Surgical approaches for various Wilms tumor conditions:
Radical nephrectomy if opposite kidney is normal and functional.
For tumors deemed inoperable at surgical exploration, open biopsy is obtained.
Incisional biopsy of both kidneys for surgical staging
Definitive surgery after chemotherapy:
Renal vein involvement
- En bloc excision of the tumor and thrombus
Adjacent organ involvement
- Initial surgery limited to biopsy
Persistent lung metastases:
- scattered superficial lesions
- deep-seated lesions
Surgical complications can occur in 20% of all Wilms tumor patients undergoing primary nephrectomy.
Complications of Wilms Tumor Surgery:
Risk factors for surgical complications: