Wilms tumour – the surgical issues

SYMPOSIUM: ONCOLOGY

Wilms tumour e the surgicalissuesSimon N Huddart

AbstractComplete surgical excision is an essential component of the management

of Wilms tumour. With successful surgery, complications should be below

10% and overall survival over 90%. Such surgery may be challenging and

should be concentrated to those few surgeons in the UK who perform

more than five or six cases per year.

Keywords CCLG; excision; nephrectomy; nephroblastoma; SIOP; Wilms

Introduction

Nephroblastoma was first described by Max Wilms in 1899.

Before multimodal therapy, surgery was the only option and

survival rates were fewer than one in five. Despite the intro-

duction of effective chemotherapy and radiotherapy (for

advanced stages) surgery still remains an essential element of the

management. Today with surgery and adjuvant chemo/radio-

therapy, survival is over 87%. Per and perioperative deaths are

very rare except when large tumours present ruptured following

trauma.

Surgery for a Wilms tumour is seldom an emergency and can

be challenging. The most experienced oncological specialist

paediatric surgeon available should undertake it and care of the

child should be under a multidisciplinary paediatric oncology

team.

Diagnosis

The majority of Wilms tumours are asymptomatic for the early

course of the disease e thus the tumours may present very large.

Often it is the parent or clinician who identifies a large lateral

mass during bath time or routine examination respectively. Like

several of the large tumours of infancy, Nephroblastoma may

present as malaise and loss of energy with a slowly enlarging

abdominal mass e late or mis-diagnosis is not uncommon.

Less commonly, haematuria (15%), abdominal pain (10%)

fever (20%) or hypertension (10%) is the presenting complaint.

Classically also, a left Wilms tumour may present as a left vari-

cocele due to tumour effects on the renal vein (into which the

gonadal vein is a tributary) e see Figure 1.

Children with predisposing conditions such as Beckwithe

Wiedermann, hemihypertrophy, Aniridia (Wilms tumour, anir-

idia, genitourinary anomalies, mental retardation e WAGR) or

Denys Drash (nephrotic syndrome, ambiguous genitalia) should

Simon N Huddart MA MBBS FRCS FRCS(Paeds) Consultant Paediatric

Surgeon, Department of Paediatric Surgery, University Hospital of

Wales, Cardiff, UK. Conflict of interest: none declared.

PAEDIATRICS AND CHILD HEALTH 24:4 137

receive regular USS scans of their kidneys. Thus, asymptomatic

tumours may be identified at an early stage.

Rarely the tumour may rupture following relatively minor

trauma e or present as cardiac arrhythmia or fatal pulmonary

embolus e see Figure 2.

Differential diagnosis

Whilst 90% of the renal tumours of childhood are Wilms,

rhabdoid tumour and clear cell carcinoma may also occur. The

prognosis for these two latter is worse than that for Wilms, but

the surgery is essentially the same. Diagnosis should be

confirmed by Trucut biopsy to ensure appropriate chemotherapy

regimens are employed.

Congenital mesoblastic nephroma accounts for 2% of renal

tumours, usually in infancy and carries a good prognosis

following successful surgery.

Xanthogranulomatous pyelonephritis (XGP) is a benign

chronic inflammation of the kidney, which may present with

fever and anaemia. The renal mass can usually be distinguished

from Wilms tumour on ultrasound, but a Trucut biopsy may be

required.

One criticism of the original SIOP guidelines (Chemotherapy

without biopsy) was that chemotherapy was given prior to open

surgery without prior Trucut biopsy. A very small number of

XGP cases or clear cell tumours etc were therefore liable to be

erroneously treated.

Other tumours which may present as a right renal mass

include:

� Neuroblastoma e urinary catecholamines are usually

raised.

� Hepatoblastoma e should be identifiable on USS.

� Teratoma e may have raised Alfa feto-protein and/or

HCG.

Whilst benign conditions such as Pelviureteric junction

obstruction may present as a large renal mass, a USS should

distinguish these from malignancy.

Pre-op investigations

Oncological

� USS e usually correctly identifies the Wilms diagnosis.

� Pre-operative plain chest X-ray in two planes (pulmonary

metastases).

� CT e further identifies pulmonary metastases, confirms

normality of contralateral kidney, may identify nephro-

blastomatosis, should identify venous tumour extension

Figure 3.

� MRI e further delineates venous extension.

� AFP/HCG e to exclude malignant teratoma.

� 24 hour Urinary catecholamines e to exclude

neuroblastoma.

Trucut biopsy

This is strongly advised in the UK to obtain tissue diagnosis prior

to pre-operative chemotherapy (usually 6 weeks). Several cores

of 12e14G are recommended under USS control. Consideration

should be given to siting the biopsy entry wound where it can be

excised in the nephrectomy procedure.

� 2013 Published by Elsevier Ltd.

http://dx.doi.org/10.1016/j.paed.2013.09.001

Figure 1 A left sided varicocele in a 2-year-old boy with a large left sided

Wilms tumour.

Figure 3 CT scan of large left sided Wilms tumour e no venous involve-

ment is shown.

SYMPOSIUM: ONCOLOGY

In the United Kingdom and most of Europe, the protocol of

SIOP (Societe Internationale Oncologie D’Pediatrique) will be

followed.

In this protocol, the diagnosis of Wilms and whether it is

favourable or unfavourable histology is first confirmed by Trucut

biopsy samples taken under ultrasound guidance. The chemo-

therapy regimen is given pre resection appropriate to the tumour

stage and histology. (Fine needle aspiration or Trucut biopsy

does not upstage the tumour). A 10-year-trial in the United

Kingdom was completed in 2001. UKW3 randomizing early stage

Wilms to primary surgery or surgery post 6 weeks of Vincristine.

Figure 2 Post mortem finding of a massive Wilms tumour embolus.


The trial favoured prior treatment with chemotherapy e intra-

operative rupture was reduced from 15% to essentially zero,

there was less blood loss and stage II and III tumours were

downgraded.

In the USA, surgery is performed as initial management of the

tumour, and then chemotherapy/radiotherapy is given depen-

dant on stage and histology. The advantage is that a “true” stage

of tumour at presentation is achieved and histology is not

affected by prior chemotherapy. The main disadvantages are an

increase in the risk of tumour rupture at surgery, which can

upstage a stage I tumour to stage III.

Gow et al recently reported the results of the Children’s

Oncology Group renal tumours committee. Of 1,131 primary

nephrectomies, tumour spill occurred in 9.7%, with an addi-

tional 1.8% having possible spill during renal vein or IVC tumour

nephrectomy. Large tumours (more than12 cm) and those on the

right were more at risk.

As surgery is only an emergency in the rare cases of tumour

rupture with uncontrolled bleeding, in the majority of cases,

surgery should be a planned procedure by the most experienced

surgical team available. The surgeon should make themselves

familiar with the various aspects of the SIOP surgical protocol

prior to the operation:

Computerized tomography e CT and ultrasound scans of the

tumour(s) should be studied prior to the operation. In particular,

any suspicious hilar or para-aortic lymph nodes should be noted

with a view to excision biopsy. Also, any tumour involvement of

the renal vein or IVC should be identified (vide infra).

Staging of Wilms tumour

Stage I

� The tumour is limited to the kidney or surrounded with a

fibrous capsule if outside the normal contours of the kid-

ney. The renal capsule or pseudocapsule may be infiltrated

with the tumour but it does not reach the outer surface,

and it is completely resected (resection margins “clear’)

� The tumour may be protruding (“bulging’) into the pelvic

system and “dipping’ into the ureter (but it is not infil-

trating their walls)



SYMPOSIUM: ONCOLOGY

� The vessels of the renal sinus are not involved

� Intrarenal vessel involvement may be present

Fine needle aspiration or percutaneous core needle biopsy

(Trucut) does not upstage the tumour.

The presence of necrotic tumour or chemotherapy-induced

change in the renal sinus and/or within the peri-renal fat

should not be regarded as a reason for upstaging a tumour

providing it is completely excised and does not reach the resec-

tion margins.

Stage II

� The tumour extends beyond kidney or penetrates through

the renal capsule and/or fibrous pseudocapsule into peri-

renal fat but is completely resected (resection margins

“clear”)

� Tumour infiltrates the renal sinus and/or invades blood

and lymphatic vessels outside the renal parenchyma but it

is completely resected

� Tumour infiltrates adjacent organs or vena cava but is

completely resected

Stage III

� Incomplete excision of the tumour, which extends beyond

resection margins (gross or microscopical tumour remains

post-operatively) - including non resection because tumour

extends into vital structures

� Any abdominal lymph nodes are involved

� Tumour rupture before or intra-operatively (irrespective of

other criteria for staging).

� The tumour has penetrated through the peritoneal surface

� Tumour implants are found on the peritoneal surface

� The tumour thrombi present at resection margins of ves-

sels or ureter, transected or removed piecemeal by surgeon

� The tumour has been surgically biopsied (wedge biopsy)

prior to pre-operative chemotherapy or surgery

The presence of necrotic tumour or chemotherapy-induced

changes in a lymph node or at the resection margins is regar-

ded as proof of previous tumour with microscopic residue and

therefore the tumour is assigned stage III (because of the possi-

bility that some viable tumour is left behind in the adjacent

lymph node or beyond resection margins.)

Stage IV

Haematogenous metastatic disease beyond stage III e e.g. lung,

liver or bone.

Stage V

Bilateral disease.

Each side should be staged according to the above criteria

prior to surgery.

Surgical exploration

Oncological surgeons should refresh their knowledge of the

surgical protocols (SIOP or COG) prior to nephrectomy.

Gross in 1953 established the principles of nephrectomy for

paediatric malignancy. He recommended early ligation of the

renal vessels, particularly the renal vein to avoid inadvertent

displacement of a renal vein tumour embolus. With modern

imaging, a venous embolus should be identified pre-operatively.


Except in the rare case of tumour rupture, the nephrectomy is

an elective operation and should be carried out by the most

experienced surgical team.

A generous transverse, transperitoneal abdominal incision on

the side of the tumour is recommended e although if the CT scan

clearly shows no involvement of the contralateral side, it is no

longer necessary to physically explore the other kidney. The

needle tract of the Trucut biopsy site should be included in the

surgical wound resection.

The abdomen should be examined for liver, lymph node and

peritoneal metastases, with complete excision recommended

(where possible and without major morbidity) if these are found.

The position of any resected lesion should be marked to facilitate

future radiotherapy. Normal lymph nodes of the hilum and peri

vascular sites should also be biopsied and sent in individual

containers to a pathologist (who has been pre-warned to expect

the samples).

Excision biopsy sampling of the hilar, and para-aortic lymph

nodes should be undertaken, with clear separate labelling of

samples. Lymph node sampling is critically important, despite

the absence of abnormal nodes on pre-operative imaging, or

upon gross inspection during operative exploration, since a re-

view of lymph node sampling by the NWTS demonstrated a false

negative rate of 31% and a false positive rate of 18% based on

pre-operative and intra-operative assessment.

Radical lymph node dissection, however, does not enhance

survival and is not recommended.

Intravascular extension of the tumour should be identified on

pre-operative imaging, but the renal vein and IVC should also be

carefully examined at an early stage of the operation.

The Wilms tumour resection commences with dissection of

the Gerota’s fascia to allow for displacement of the tumour

anteriorly enabling safe dissection of the renal vessels. Where

the tumour is of moderate size, early ligation of the vessels

should be the aim. Kocher’s manoeuvre (displacement of the

duodenum medially) may be helpful for both left and right

tumours.

In very extensive or adherent tumours, isolation of the hilar

vessels prior to mobilization of the tumour may be theoretically

desirable, but such vessels are frequently distorted and/or sur-

rounded by tumour and such dissection risks major haemorrhage

and/or damage to the aorta/IVC or major mesenteric or coeliac

vessels. With modern imaging, tumour involvement of the renal

vein or IVC should be known prior to surgery. In such cases, the

dissection should be taken around the tumour first to allow for

safe ligation of the vessels when possible.

The renal artery should ideally be ligated first to avoid

engorgement of the tumour. It is important that the vessels are

ligated separately to avoid the possibility of a renal vessel

vascular shunt and subsequent high output cardiac failure.

Anomalous oncogenic vessels are frequently encountered origi-

nating from the psoas muscle together with a leash of neo-

vascularity around the ureter and gonadal vesselse these should

be sought and dealt with to maintain a bloodless field.

Great care must be taken to avoid tumour rupture which

potentially upstages the tumour from stage I to stage III. Some

tumours have a thin capsule at risk of rupture, especially if they

have not received prior chemotherapy (NWTS rupture rate 10%

c.f. CCLG under 1%).



Figure 4 Heminephrectomy for a right sided upper pole tumour. The

vascular demarcation is shown after ligation of the right upper pole

vessels.

SYMPOSIUM: ONCOLOGY

The anatomy of the renal vessels is such that the left renal

vein is far longer than the right, and on the whole a left tumour

nephrectomy is far easier than a right. On many occasions with a

large tumour, the right vein may be a thin wide strip stretched

over the tumour. In such cases, a generous Kocher’s manoeuvre

together with full dissection of the tumour prior to vein control

should allow safe (double) ligation. Ligation must be secure, as a

failed suture back on the ward would prove fatal before a child

could be returned to theatre. The surgeon should avoid “tenting”

the IVC during ligation to prevent an elliptical IVC breach when

the suture falls back. It should also be within any oncological

surgeon’s armamentarium that an IVC breach could be safely and

swiftly corrected.

Particular care should be taken to ensure that the correct

ipsilateral renal vessel is the one being ligated. With very large

tumours, the anatomy may be distorted such that the contralat-

eral vessel is the first encountered. Clearly such an error would

have disastrous consequences.

The unilateral adrenal gland should be left in situ where the

plain of dissection has not been breached by tumour.

The ureter should be taken as close to the bladder as possible

as Wilms tumour not infrequently invades down the ureter.

Laparoscopic approach to nephroureterectomy is being re-

ported, but an incision (e.g. pfannensteil) is still required, and

the technique is only suitable for the smaller Wilms tumours.

The larger tumours and those with renal hilar involvement

should be resected by open technique.

Some surgeons have extended laparoscopic resection to

bilateral, stage 5 partial nephrectomies, again for the smaller

nodules associated with nephroblastomatosis.

Tumour involving the renal vein, IVC

Approximately 2e3% of children will present with tumour

extension to the renal vein or IVC. The exact extent of the tumour

should be determined pre-operatively with ultrasonography/

Doppler scans, echocardiography, CT and MRI scanning. A

detailed plan for surgery should then be made.

A short embolus in the renal vein may be resected along with

the kidney.

Tumour extending intrahepatically can be excised after

proximal and distal control of the IVC is achieved. Where tumour

extends to the level of the liver but remains infra-diaphragmatic,

the liver may be mobilized medially (division of lateral liga-

ments) to allow control of the IVC posterior to the liver.

Any tumour extending supra-diaphragmatically can be

resected utilizing cardio-pulmonary bypass and deep hypother-

mia and circulatory arrest.

Bilateral e stage V e Wilms tumour

Around 5% of children present with bilateral disease, particu-

larly in those with a predisposing syndrome e WAGR,

BeckwitheWiedermann, DenyseDrash.

Around 90% of children should be able to be treated with

bilateral partial nephrectomies. Nephron sparing surgery has

been advocated for stage V tumours (to avoid the need for dial-

ysis/transplant) but also for unilateral tumours to reduce the

possibility of compensatory hypertrophy and decreased renal

function over time Figure 4.


Where required, “bench surgery” may be undertaken on the

kidney to remove the tumour prior to re-implantation.

Overall the results of such surgery have been satisfactory,

although there have been reported complications of residual

tumour left in situ, gross haematuria, and urinary leak (25%).

For a partial nephrectomy, the aim should be to achieve a

surrounding margin of healthy normal renal tissue e enucleation

is not recommended.

Contraindications for partial nephrectomy

� pre-operative tumour rupture or biopsy

� tumour infiltrating extra renal structures

� intra-abdominal metastases or lymph nodes seen on pre-

operative imaging

� thrombus in the renal vein or vena cava

� tumour involving more than 1/3 of the kidney (at least

50% of renal tissue should be spared after the tumour

resection with a margin of healthy tissue, to give any

worthwhile protection against hyper perfusion)

� multifocal tumour

� central location

� involvement of calyces

� haematuria

� little experience in partial nephrectomy

Lung metastases

The management of a child with Wilms tumour should always be

under a multidisciplinary oncological team (oncologists, sur-

geon, pathologist and radiotherapist). Where lung metastases are

visible on chest CT scan following chemotherapy, there may be a

role for surgical excision e either via open thoracotomy, or

thoracoscopic resection. (the latter has the disadvantage that

small metastases cannot be digitally felt). CT guide wire location

prior to resection may be useful. Early surgical excision of lung

metastases is reserved for those where the viability of pulmonary

tumour is in doubt, and histological confirmation of necrotic or

scar tissue would obviate lung radiation.



Figure 5 Excision of a large recurrent Wilms tumour via a thoraco-

abdominal approach.

Figure 6 Excision of a right Wilms tumour.

SYMPOSIUM: ONCOLOGY

Bilateral pulmonary metastases may be approached by two

thoracotomies, or a midline sternotomy as appropriate. The aim

should be wedge radical excision or lobectomy if that is not

feasible. A pneumonectomy is contra-indicated.

Jehovah’s witnesses

Where the parents of a child with a nephroblastoma are Jeho-

vah’s witnesses, clearly every care must be taken to avoid the

need for a blood transfusion. Although in the UK a judicial ruling

may be enforced to permit the giving of blood despite the par-

ents’ wishes, in practice this is rarely necessary. Even with very

large tumours, careful dissection, use of CUSA and bipolar

dissection and red-cell saving will result in very little blood loss.

The child may also be pre-prepared with erythropoietin and the

use of Aprotinin� (Trasylol e SigmaeAldrich) per op will

reduce capillary blood loss.

Early complications from Wilms nephrectomy

The National Wilms tumour study group in the USA reported

their results in 2001. They found that 12.7% of children had

complications, including intestinal obstruction (5.1%), extensive

haemorrhage (1.9%), wound infection (1.9%) and vascular

injury (1.5%).

Not surprisingly, complications were more likely if the

tumour extended into the IVC or right atrium, but they were also

seen more often when a flank incision was used rather than a

lateral intraperitoneal approach. Other high risk factors included

a tumour greater than 10 cm diameter ( p ¼ 0.05; OR 2), and

when the surgery was performed by a general surgeon ( p ¼ 0.03,

OR 9) rather than a paediatric surgeon.

SIOP publications have shown that operative complications

are reduced to under 8% if chemotherapy is given prior to

surgery.

Intestinal obstruction may be due to early postoperative ileus,

which should settle on conservative management (gastric

drainage and intravenous fluids/feeds) but may also be due to

intussusception. Intussusception may be more common than is

recognized and careful clinical and radiological examinations are

required to avoid unnecessary sequelae. Early or late adhesion of

the small bowel e usually down to the right paracolic gutter site

of nephrectomy may require re-operation.

Surgical treatment of relapse

The success rate of treatment of first relapse is high and the

intention should be to cure. Initial management is with second

line chemotherapy, with surgical resection where relapse sites

allow after a response to chemotherapy has been shown. The aim

should be complete resection with titanium clip identification of

sites to focus subsequent radiotherapy Figure 5.

Long term outcomes from surgery

As the cure rate for Wilms tumours in childhood has increased,

the long term effects of the surgery and adjuvant treatment are

becoming more obvious. Most of these are due to the effects of

radiotherapy (above 1200 cGy) and/or chemotherapy (ifosfa-

mide, etoposide), but nephrectomy in an infant can lead to

compensatory hypertrophy and hyperfiltration syndrome.


Compensatory hypertrophy of the remaining contralateral

kidney may develop to give proteinuria and reduced renal

function due to focal glomerulosclerosis. This is exacerbated if

the child has received radiotherapy that has extended over to the

contralateral side. Experiments have shown hyperfiltration syn-

drome occurs if less than 25% renal mass remains (e.g. stage V,

unilateral nephrectomy, contralateral partial nephrectomy) but it

has also been seen clinically after only one kidney has been

removed.

End stage renal disease due to chronic renal failure 20 years

after Wilms surgery has been reported in 0.7% of children. Early

age at diagnosis, stroma predominant histology and bilateral

tumours were risk factors. Should renal transplant be required, it

has been recommended that at least 2 years disease free survival



SYMPOSIUM: ONCOLOGY

occurs first to avoid increasing the risk of immunosuppression

metastases.

Conclusion

Complete surgical excision of a Wilms tumour is an essential

component of the management of this malignancy. With suc-

cessful surgery, complications should be below 10% and overall

survival over 90%. Such surgery may be challenging and should

be concentrated to those few surgeons in the UK who perform

more than five or six cases per year Figure 6. A

FURTHER READING

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surgery for unilateral primary renal tumor in children. J Pediatr Surg

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Davidoff AM, Giel DW, Jones DP, et al. The feasibility and outcome of

nephron-sparing surgery for children with bilateral Wilms tumor. The

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of pulmonary metastasis less than 1 cm. J Laparoendosc Adv Surg

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intraoperative tumor spill: report from the Children’s Oncology

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Gross RE. The surgery of infancy and childhood. Philadelphia: WB

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Wilms tumour – the surgical issues