Neoplasms of the kidney (Table 64.7)
Benign
neoplasms
Adenoma.
Pea-like cortical adenomas are occasionally discovered at post
mortem examination or incidentally during radiological imaging. They are
asymptomatic and by definition benign.
Angioma
may cause profuse haematuria, often in young adults. The source of the bleeding
may be difficult to diagnose without renal angiography.
Angiomyolipoma
is an unusual tumour of the kidney which is often but not always associated with
tuberous sclerosis. Its high fat content gives it a typical appearance on CT.
Malignant elements are present in about a quarter of them and may lead to
metastasis.
Malignant
neoplasms
Benign
tumours of the kidney are rare and it is a good rule that all neoplasms of the
kidney which are recognised clinically should be treated as malignant. They are
uncommon between the ages of 7 and 40.
Renal neoplasms
in children
Wilms’ tumour
(syn. nephroblastoma)
This is a mixed tumour containing epithelial
and connective tissue elements arising from embryonic nephrogenic tissue. The
tumours are usually discovered during the first 4 years of life. They are
normally in one or other pole of one kidney, but bilateral tumours occasionally
pose a difficult clinical problem.
Pathology.
The cut surface of the tumour is grayish or pinkish white. A rapidly growing
tumour is likely to be soft and friable in consistency (Fig.
64.38).
Microscopically
the tumour
is composed of epithelial and connective tissue cells, occasionally with islands
of bone, cartilage and muscle fibre. Some of the elements in this cellular
mixture may be less sensitive to radiotherapy than others.
Clinical features.
Abdominal tumour. An abdominal tumour appears which grows rapidly while the general well being of the child deteriorates. The mass may be enormous compared with the tiny patient.
Pyrexia, which is a feature in half of these patients, disappears when the
tumour is removed.
Haematuria denotes extension of the tumour into the renal pelvis and the prognosis
is not so good.
Imaging
by ultrasonography, urography or CT confirms a solid space occupying lesion in
the kidney.
Metastasis
occurs early, mainly by the bloodstream to the lungs. Liver and bone metastases
are rare; and brain metastases even more so. Lymphatic spread is uncommon.
The
presence of bone secondaries favours a diagnosis of nephroblastoma, another
renal tumour of childhood which is treated in the same way as Wilms’ tumour.
Treatment.
These children do best when treated in
specialist units. Nephrectomy
should be performed as soon as possible and followed by radiotherapy with
or without chemotherapy. Partial
nephrectomy may be possible in patients with bilateral disease.
Prognosis.
Under 1 year of age 80 per cent survive for 5
years, but the prognosis is less good in older children. Recurrences
usually occur within a year, so a child surviving for 18 months or more is
probably cured.
Renal neoplasm
in adults
Hypernephroma (syn.
Grawitz’s tumour)
This is an adenocarcinoma and is the most common neoplasm (75 per cent) of the kidney. It arises from renal tubular cells. Whether carcinoma arises in pre-existing adenomas is a matter for dispute.
Pathology.
Moderate sized tumours are spherical and often occupy the poles of a single
kidney, most commonly the upper pole. Tumours in the hilum are less common. The
cut surface of the tumour is usually yellowish or dull white, semitransparent,
with areas of haemorrhage (Fig. 64.39). The tumour is often divided into lobules
by fibrous septa, some of which are cystic. Larger tumours are irregular in
shape with central haemorrhage and necrosis.
Microscopical structure. The most common
pattern is of solid areas of polyhedral or cubical clear cells with deeply
stained small rounded nuclei and abundant cytoplasm containing lipids,
cholesterol and glycogen. The cells are occasionally arranged as papillary cysts
or tubules. Less commonly the cells are granular (dark), and both clear and dark
cells may be represented in the same tumour. In all cases the stroma is scanty
but rich in large blood vessels.
Spread.
The tumour is prone to grow into the renal vein. Pieces of growth are swept into
the circulation and end up in the lungs where they grow to form cannonball
secondary deposits (Fig. 64.40). Metastasis to bone also occurs and a secondary
deposit in a long bone may remain the only sign of distant spread for a year or
more. Highly vascular metastases may pulsate. If the tumour extends beyond the
renal capsule it is liable to metastasise via the lymph nodes in the hilum of
the kidney to the para-aortic nodes and beyond.
Clinical features. Hypernephroma is twice as common in men as in women. Haematuria is usually the presenting symptom, sometimes with clot colic. There may be a dragging discomfort in the loin or the patient may detect a mass. In men, a rapidly developing varicocele is a rare but impressive sign, occurring most often on the left side because the left gonadal vein is obstructed where it joins the left renal vein.
Atypical presentations.
1. In 25 per cent of cases there are no local symptoms. The patient
presents with symptoms due to secondary deposits such as a painful enlargement
of a long bone (Fig. 64.41), a pathological fracture, persistent cough or
haemoptysis.
2. Occasionally persistent pyrexia
(37.8—38.90C) is the only symptom. There is no evidence of
infection. Persistence of the pyrexia after nephrectomy suggests the presence of
metastases.
3.
A small number of patients presents with constitutional symptoms and is
found to be extremely anaemic.
4. Polycythaemia occurs in 4 per cent of cases
as a result of the production of erythropoietin by tumour cells. The erythrocyte
sedimentation rate is always raised above the 1—2 mm found in idiopathic
polycythaemia vera. The blood count returns to normal after nephrectomy unless
there are metastases. Other hormones, such as renin and calcitonin, may be
produced by the tumour. Hypercalcaemia is common.
5. Nephrotic syndrome has been reported as a rare presentation of
hypernephroma.
Investigation.
Intravenous urography is still an
important component of the investigation of haematuria. The plain radiograph may
show abnormal calcification in the tumour and distortion of the renal outline
which will be confirmed on the nephrogram film. The calyces may be stretched and
distorted. It is important to know whether the contralateral kidney is working (Fig.
64.42).
Ultrasound and CT
Once a mass has been demonstrated in the kidney a scan is needed to
decide whether it is solid or cystic. Modern high-definition ultrasound will
give this information. CT with enhancement will demonstrate the extent of the
lesion more clearly and will show whether there is hilar lymphadenopathy or
renal vein involvement (Fig.
Renal angiography is used less since CT became available. Enthusiasm for preoperative
embolisation of hypernephroma has waned. Occasionally a flush inferior cavagram
is helpful to show the extent of caval involvement by tumour growing in from the
renal vein.
A chest radiograph is essential to detect lung secondaries. An isotope bone scan will
reveal deposits in the skeleton.
Treatment.
If the tumour is confined to the kidney treatment is nephrectomy with removal
of the perinephric fat.
Nephrectomy can be performed through a loin or
a transverse or oblique upper abdominal incision. The transabdominal approach
has the advantage that the renal pedicle and the inferior vena cava can be
widely exposed.
The
vascular pedicle should be ligated before the kidney is mobilised because
handling the tumour may cause malignant cells to be released into the
circulation. The first step in the procedure is to clean the renal artery and
ligate it in continuity. This may be more difficult from an anterior approach
because the vessel lies behind the
vein. However, once the artery is occluded the tumour loses most of its profuse
blood supply and massive bleeding during mobilisation becomes less likely. The
renal vein should be gently palpated to be sure that it does not have tumour in
its lumen. If it is empty, it can be divided between ligatures. The renal artery
is then divided and the kidney mobilised within its fascial and fatty coverings.
Troublesome bleeding can still occur when aberrant vessels feeding the tumour
are divided, and these must be carefully ligated or coagulated. The ureter is
then traced downwards as far as is safe and divided between ligatures.
If
the renal vein or the inferior vena cava is invaded the surgeon must obtain
control of the cava above and below as a first priority. If there is extension
into the thorax, the cardiac team may be needed to put the patient on cardiac
bypass so that tumour can be removed from the right side of the heart if
necessary.
Adenocarcinoma
of the kidney does not respond well to radiotherapy or conventional
chemotherapy. There have been early promising results from clinical trials of
the cytokine interleukin-2 in this condition.
Prognosis.
Removal of even the largest neoplasm may cure the patient. In operable cases 70
per cent of patients are well after 3 years and 60 per cent after 5 years. Macroscopic involvement of the renal vein or its
tributaries, tumour invasion beyond the capsule and lymph node involvement all
worsen the prognosis. These resemble those of the bladder but are
much less common. They tend to invade the renal parenchyma and have a tendency
to distant spread. There is a strong tendency for the tumours to be multifocal.
Seeding down the lumen of the urinary tract may give rise to multiple ureteric
tumours, but the condition is thought to arise from a field change which renders
the whole urothelium liable to metaplasia. Whether the carcinogen is chemical or
viral is uncertain in most cases.
Clinical
features. Haematuria is the most common symptom and usually causes the patient
to seek help before the tumour mass becomes palpable.
Urine
cytology. Examination of the urine for the presence of malignant cells may
indicate whether the tumour is well or poorly differentiated. There is some
evidence that those with poorly differentiated tumours do better if they have a
short course of radiotherapy before surgery. It is therefore useful to obtain
cells from the tumour by sampling using a brush or catheter passed up the ureter
under radiological control.
Intravenous
urography usually demonstrates the tumour (Fig.
64.45). Retrograde pyelography
may be helpful if the urogram is indistinct.
Treatment. Conventional surgical treatment is by nephroureterectomy. The ureter must be disconnected with a cuff of bladder wall. If this is done by open surgery a second incision is needed to remove the kidney. Alternatively, the ureteric orifice can be widely resected with a resectoscope and the ureter delivered by a somewhat perilous blunt dissection from the upper abdominal wound used to remove the kidney. This pluck operation is not for the inexperienced. Some urologists argue that well-differentiated upper urinary tract transitional tumours should be treated conservatively like superficial bladder tumours. However, percutaneous resection of these cancers is controversial and steps must be taken to avoid the growth of tumour seeded in the percutaneous track.
Squamous
cell carcinoma of the renal pelvis
This is rare and often associated with chronic inflammation and
leucoplakia
resulting from stone. The tumours are radiosensitive but metastasise at an early
stage and the prognosis is poor.
Transitional
cell tumours of the ureter
These are rare. They behave like tumours of the renal pelvis. Treatment
is by nephroureterectomy.
About one half of patients with tumours of the upper
urinary tract will have tumours in the bladder at some stage. Follow-up by
cystoscopy with regular urography is therefore necessary to detect recurrent
tumours.
Balkan
nephropathy. Transitional cell tumours of the upper urinary tract have a very
high incidence in certain areas of the former Yugoslavia. They also have a high
incidence of a form of primary nephropathy. The causative agent has not been
identified with certainty but there seems to be an association with the
consumption of grain products stored in a damp environment. Tumours which
develop against a background of Balkan nephropathy should be treated by
conservative surgery in view of the impaired overall renal function.
Nephrectomy for
benign disease
Nephrectomy is now rarely performed for benign
disease but may be necessary if the kidney is atrophic or dysplastic or the
cause of accelerated hypertension. Nonfunctioning kidneys resulting from
longstanding obstruction or stone disease are a potential site for infection
and even malignancy Because they do not excrete they cannot be properly seen on
an excretion urogram and it is often wisest to perform a simple nephrectomy. In
a simple nephrectomy the kidney is dissected free though the convenient plane
between the capsule and its fatty coverings. If this plane is obscured by the
scarring of previous surgery a subcapsular nephrectomy may be safer.
Laparoscopic nephrectomy is sometimes possible for small kidneys destroyed by
benign disease but the technique requires special skills and the costs and
benefits are under evaluation.