Wilms' tumour


GE Healthcare
Search Medcyclopaedia for:
 
Search marked text (mark text before you click)
Browse entry words starting with:
A B C D E F G H I J K L M
N O P Q R S T U V W X Y Z
Other characters





 Medcyclopaedia™ About Medcyclopaedia™ amershamhealth.com


Wilms' tumour,
 Print this article

(Max Wilms, 18671918, German surgeon) (also called nephroblastoma), malignant tumour of the kidney, usually arising from nephroblasts, is the most common genitourinary malignancy in children, accounting for 95% of malignancies affecting the genitourinary tract and 8% of childhood malignancies. The peak incidence is between 1 and 3 years, with 70% occurring in children under 4 years and 90% under 7 years. It occurs with equal frequency in boys and girls. It is extremely rare in the neonatal period. There are associated or predisposing anomalies such as aniridia, hemihypertrophy, Beckwith Wiedemann syndrome and Drash syndrome as well as various genitourinary anomalies. There is up to 10% incidence of bilateral occurrence, two thirds of which are synchronous and one third metachronous. Metachronous tumours may really be undetected, small, synchronous tumours at the time of the initial diagnosis of Wilms' tumour.

The clinical presentation of children with a Wilms' tumour is usually with an abdominal mass although occasionally with pain, haematuria and non-specific signs such as fever. A few patients may present with hypertension. A variocele due to tumour obstruction of the left gonadal vein is a rare presentation.

Imaging

Ultrasound demonstrates a renal mass, often large. The pattern varies from homogeneous to one of mixed hyperechogenicity, with hypoechoic areas (Fig.1) indicative of cystic degeneration or necrosis, and there may be areas of haemorrhage. Calcification may occur in up to 15% of patients but not as prominently as in neuroblastoma. The tumour may infiltrate the renal vein and extend into the inferior vena cava in between 5% and 10% of patients. The thrombus can be detected and flow assessed with Doppler. Tumour thrombus may also extend into the right atrium. The primary tumour may extend to compress or infiltrate the collecting system and cause obstruction with dilated calyces. Metastasis to lymph nodes may be seen and may elevate the inferior vena cava. Lymphadenopathy is not specific and may, if not prominent, be reactive, and not necessarily due to metastases. It is very important to evaluate the rest of the kidney, and the contralateral kidney, for tumour or nephroblastomatosis.

Preoperative assessment with contrast enhanced CT will show the extent of tumour to better advantage than ultrasound and also assess gross function. Nonfunction may be due to tumour invasion obstructing the renal veins or the renal pelvis (Fig.2). The tumour appears as a large, spherical mass lying within the kidney with attenuation slightly lower than that of the normal renal parenchyma on unenhanced scans. The tumour enhances less than the normal renal tissue. In up to 80% of cases the tumour appears heterogeneous with solid areas and areas of low attenuation representing necrosis, cystic degeneration or haemorrhage. Calcification can be seen in 15% of cases on CT although most of this is not visualized on a plain film. Occasionally the tumour may be almost entirely cystic. Owing to compression or invasion of the hilar vessels or collecting system, there may be poor or absent function, which occasionally may be due to extensive infiltration of the whole kidney. Involvement of the inferior vena cava and lymphadenopathy is readily seen on CT.

MRI is used in difficult cases, especially when ultrasound and CT show equivocal thrombus, when MR venography can be helpful. The primary tumour shows low intensity on T1-weighted sequences with necrotic areas that have a lower intensity than tumour. Fresh haemorrhage shows as a high signal. On T2 there is increased signal intensity although this is usually lower than that of normal renal tissue. Tumour thrombus can be readily identified on MRI (

Encapsulated tumour without capsular breach
STAGE IICapsular breach or tumour extending across the midline
STAGE IIIAs for II with local lymph node metastases
STAGE IVDistant metastases

Ifosfamide is used in treating aggressive Wilms' tumours and may lead to the development of iatrogenic rickets.


AD


The Encyclopaedia of Medical Imaging Volume VII
Wilms' tumour, Fig. 1
Ultrasound of the lower pole of the right kidney demonstrating loss of the normal architecture of the kidney with replacement by a solid lesion of low echogenicity. These are the appearances of a small Wilms' tumour.
Wilms' tumour, Fig. 2
CT scan with oral and intravenous contrast medium, of a left Wilms' tumour. The tumour contains multiple areas of necrosis. A small residuum of renal tissue lies compressed medially. The inferior vena cava and aorta are normal.
Wilms' tumour, Fig. 3
T1-weighted MRI in the coronal plane showing the left kidney replaced by tumour. The areas of reduced signal intensity represent necrosis. The aorta is displaced medially. There is tumour embolus, seen as a long, linear area of reduced signal in the inferior vena cava (IVC), which is also widening the IVC. The tumour thrombus extends to the right atrium.