Teaching Case

A 3-year-old female child was brought by her parents with insidious onset abdominal distension with no associated nausea, vomiting, abdominal pain, fever, altered bowel habits or haematuria. Birth history was normal. Blood investigations were unremarkable.

Initial imaging with plain radiograph and ultrasound of abdomen revealed a large mass lesion involving the left side of abdomen, the possibility of renal malignant lesion was considered. Contrast CT of abdomen and pelvis showed grossly enlarged left kidney with multiple heterogeneously enhancing mass lesions within it involving the upper pole, lower pole and interpolar region causing displacement of adjacent organs and structures. Non-enhancing areas were present suggesting necrosis within, with no evidence of areas of calcifications or fat attenuations. The lesion was causing malrotation of the left kidney. There was neither crossing of the lesion noted to opposite side nor any neural foraminal extensions. There were no evidence of any distant metastasis to lungs, adjacent organs,  IVC or renal vein.

Wilms tumour, also known as nephroblastoma is the most common pediatric malignant renal neoplasm typically occuring in early childhood (1-11 years), with peak incidence between 3 and 4 years of age. The tumour usually arises in a single kidney. Synchronous bilateral or multifocal tumours occur in approximately 10% of patients and tend to present at an earlier age [1]. Wilms tumour can also be diagnosed in adolescents or adults, but this is extremely rare, representing less than 1%.

Several syndromes result from a disruption of the WT1 gene, which encodes the transcription factor WT1, crucial for renal and gonadal embryogenesis. Disruption of the same typically results in genitourinary abnormalities and predisposition to early Wilms tumour [2,3,4].

The vast majority of Wilms tumours present with an asymptomatic abdominal mass. Hematuria and pain are infrequent clinical findings, but hypertension may be present in up to 25% of cases due to renin production by the tumour [5].

Atypical presentations are found in less than 10% of cases due to compression of surrounding organs or vascular infiltration. Occasionally, it may present as acute abdomen due to tumour rupture [6]. Tumour production of hormonal substances may lead to paraneoplastic syndromes, including hypercalcaemia, erythrocytosis and acquired von Willebrand disease [6].

On ultrasound, Wilms tumour is heterogenous in echotexture which can be due to a combination of necrosis, haemorrhage and calcifications within the tumour. The tumour may extend into the renal vein or IVC which is better appreciated with doppler ultrasound studies. However, MR imaging modality has proved to be the most sensitive in determining caval patency[7]. Wilms tumour demonstrates low signal intensity in T1 weighted images and high signal intensity in T2 weighted images. Final diagnosis and surgical planning are made from meticulous USG and CECT.

Mainstay of treatment is radical nephroureterectomy and lymph node sampling. Majority of patients present with large tumours, which may be unresectable making neoadjuvant chemotherapy followed by surgery the preferred approach. Histology and staging are used for risk stratification. The imaging procedure of choice is CECT of thorax/ abdomen and pelvis, which should be done at presentation, as well as for re-evaluation. Radiation therapy is recommended mainly in Stage III and Stage IV [8].

Cure rates are based on histologic findings and disease stage and have improved from 10% in the 1920s to over 90% today [9].