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. 64.43).

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.