Kidney Tumours

Kidney tumours are tumours, or growths, on or in the kidney. These growths can be benign or malignant (kidney cancer). Kidney tumours may be discovered on medical imaging incidentally (i.e. an incidentaloma), or may be present in patients as an abdominal mass or kidney cyst, haematuria, abdominal pain, or manifest first in a paraneoplastic syndrome that seems unrelated to the kidney. Other markers or complications that may arise from kidney tumours can appear to be more subtle, including; low haemoglobin, fatigue, nausea, constipation, and/or hyperglycaemia.

A CT scan is the first-choice modality for workup of solid masses in the kidneys. Nevertheless, haemorrhagic cysts can resemble renal cell carcinomas on CT, but they are easily distinguished with Doppler ultrasonography (Doppler US). In renal cell carcinomas, Doppler US often shows vessels with high velocities caused by neovascularization and arteriovenous shunting. Some renal cell carcinomas are hypo vascular and not distinguishable with Doppler US.

 Therefore, renal tumours without a Doppler signal, which are not obvious simple cysts on US and CT, should be further investigated with contrast-enhanced ultrasound, as this is more sensitive than both Doppler US and CT for the detection of hypo vascular tumours.

On renal ultrasonography, a solid renal mass appears in the US exam with internal echoes, without the well-defined, smooth walls seen in cysts, often with Doppler signal, and is frequently malignant or has a high malignant potential. The most common malignant renal parenchymal tumour is renal cell carcinoma (RCC), which accounts for 86% of the malignancies in the kidney.

 RCCs are typically isoechoic and peripherally located in the parenchyma, but can be both hypo- and hyper-echoic and are found centrally in medulla or sinus. The lesions can be multifocal and have cystic elements due to necrosis, calcifications and be multifocal. RCC is associated with von Hippel–Lindau disease, and with tuberous sclerosis, and US has been recommended as a tool for assessment and follow-up of renal masses in these patients.

The RENAL Nephrometry Scoring System is used to measure the complexity of kidney tumours for determining whether a renal mass is appropriate for partial or radical nephrectomy, and is estimated by CT scan as follows: The nephrectomy score takes into account the size of the tumour (Radius), how much of the tumour is inside or outside of the kidney (Endophytic/Exophytic), how close the tumour is to the urinary collecting system (Nearness), whether the mass is on the anterior or posterior surface of the kidney (Anterior), location relative to polar lines(Lines), and whether or not it is touching the renal artery or vein. This system is used mainly to determine appropriateness of performing a partial nephrectomy where only the tumour itself is removed, or a radical nephrectomy.

Another factor affecting complexity includes renal vein thrombus, which can extend into the inferior vena cava and into the right atrium. The degree of extension is commonly graded as follows: At level 0, the thrombus extends to the renal vein only; at level I, the neoplastic emboli extends into the IVC to no more than 2 cm above the renal vein; at level II, the thrombus reaches into the IVC to more than 2 cm above the renal vein but not to the hepatic vein; moreover at level III, the thrombus reaches into the IVC above the hepatic veins but not above the diaphragm; and finally at level IV, the thrombus extends into the supradiaphragmatic IVC or the right atrium.

No direct determinant of kidney tumours has been discovered; however, factors that put one at a higher risk of developing them include; smoking, exposure to asbestos and other chemical carcinogens, being obese and/or consuming an unhealthy diet, having a family history of cancer, and alcohol and coffee consumption.

The incidence rate of kidney tumours is greater in men than in women. The incidence of kidney tumours is more greatly distributed in North America and Europe than in Asia and South America. The incidence of small renal tumours has been increasing since the 1980s. Because kidney tumours are often difficult to detect, the advancement of diagnostic imaging has inherently been correlated with the incidence rate.

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With Regards,

David Paul

Editorial Assistant

Journal of Clinical Nephrology and Research