What is the Renal Mass on the Kidney | Ultrasound

 Ultrasound cannot reliably differentiate between benign renal tumours (others than renal cysts) and malignant renal tumours, and cannot always accurately differentiate malignant tumours from renal masses.

There are two exceptions to the above statement:

1. In the early stages, a renal angiomyolipoma has ultrasound characteristics that allow accurate recognition. These tumours can occur at any age and may be bilateral. Ultrasound images show a well-circumscribed, hyperechogenic and homogeneous mass, and as the tumour grows there will be back wall attenuation, However, some tumours will undergo central necrosis and there will be strong back wall echoes. At this stage differentiation by ultrasound is no longer possible, but abdominal X-rays may show fat within the tumours, which is unlikely to occur in any other type of renal mass.

2. When a renal tumour spreads into the inferior vena cava or into the perirenal tissues, there is no doubt that the tumour is malignant.

Solid renal mass

Renal masses may be well-circumscribed or irregular and may alter the shape of the kidney. Echogenicety may be increased or decreased. In the early stages, the majority of malignant tumours are homogeneous: if central necrosis occurs, they become non-homogeneous.

It is important to recognize normal hypertrophied columns of Bertin, which can resemble a tumour. The echo pattern of the cortex should be the same as the rest of the kidney: However, in some patients, differentiation may be difficult.

A complex non-homogeneous mass (Kidney tumour)

The differential diagnoses of complex masses can be very difficult, but when there is a spread of a tumour beyond the kidney, there is no doubt that it is malignant. Malignant tumours may also be contained within the kidney. Both tumours and hematomas may be shown acoustic shadowing due to clasification.

As tumours grow, their centre may become necrotic with a rough irregular outline and much internal debris, causing a complex ultrasound pattern. The differentiation of this from an abscess or a haematoma can be difficult. The clinical condition of the patient may indicate the correct diagnosis. Tumours can spread into the renal vein or inferior vena cava and resemble thrombosis.

Always scan both kidneys. When a malignant renal tumour is suspected (at any age), scan the liver and the inferior vena cava. Also, X-ray the chest for metastases.

A rough, irregular, echogenic mass containing debris with an enlarged kidney may be malignant or a pyogenic or tuberculosis abscess. The patient's clinical conditions may help to differentiate.

In children, malignant tumours, e.g. nephroblastoma (Wilms tumour), maybe well encapsulated but not homogeneous. Some show classification but not in the capsule. Haemorrhage or necrosis may change the echogenicity. Some are bilateral.