kidneysMost people with TSC will develop some signs of TSC in their kidneys during their lifetime. However, with proper surveillance and care, most people with TSC will not have major problems with their kidneys.

Doctors who specialize in kidneys are called nephrologists. Another term used by health professionals for things to do with the kidneys is ‘renal’ and kidney doctors are also called renal physicians. Surgeons who operate on kidneys are called urologists.

Signs and Symptoms

Kidneys can be affected by TSC in a number of ways:

Kidney Cysts and Polycystic Kidney Disease
Cysts in the kidneys are generally small and do not cause symptoms. Cysts occur in about 20 percent of people with TSC and can be seen on an ultrasound but are often not visible until adulthood.

Exactly how kidney cysts develop is not known. The TSC genes are believed to produce tumor suppressor proteins. Normally, tumor suppressor proteins prevent excess cell growth. When the TSC genes are inactivated by gene mutations, these tumour suppressor proteins are not produced and cell growth is unchecked. Cysts may, therefore, be the result of excess growth of kidney epithelial cells, which form the lining of the cysts.

Approximately 2% of people with TSC will also have autosomal dominant polycystic kidney disease (ADPKD). The gene for polycystic kidney disease is right next to the TSC2 gene. In these people with both diseases, it is believed to be caused by a large deletion that goes across both of these adjacent genes. For these people, their severe polycystic kidney disease will usually be visible during childhood or even before birth.

Angiomyolipomas (AMLs)
AMLs are a benign tumour in the kidneys made up of blood vessels (angio), muscle (myo) and fat (lipo). The presence of fat in angiomyolipomas allows them to be distinguished from other kidney tumors by MRI, CT or ultrasound imaging.

Researchers estimate that approximately 80% of people with TSC will develop AMLs during their lifetime. Although most people with TSC will develop AMLs, most people with TSC and AMLs won’t have major problems.

Kidney AMLs can cause concern if they start to bleed. Bleeding is rare in AMLs that are smaller than 4cm but the risk of bleeding increases as the size of the AML increases. This is why surveillance is so important.

A bleeding AML may cause back or abdominal pain or blood to be seen in the urine. In severe cases AMLs can result in hemorrhage and shock.

Kidney Cancer
There is some research that suggests people with TSC may have an increased risk of developing kidney cancer (renal cell carcinoma). The risk has been estimated to be between 1 and 4% and can occur at a younger age than in the general population.

These cancers are usually slow growing and if they are found early can be removed. This is another reason why surveillance is important. It may be difficult to distinguish cancers from AMLs and sometimes a CT scan, MRI or biopsy will be required.

Impaired kidney function
Most people with TSC will have normal kidney function.

Only some people with TSC experience some degree of kidney impairment. Kidney failure occurs rarely in TSC except for people who also have severe polycystic kidney disease. If kidney failure occurs dialysis or a kidney transplant are possible.

Surveillance

Surveillance is important because it can lead to early detection and treatment. Each person with TSC should have an individual management plan developed with their medical team that uses these guidelines as a starting point.

  • Renal ultrasounds should be done on diagnosis and then repeated every 1-3 years.  Yearly ultrasounds are recommended if large AMLS are present.
  • Unusual lesions (e.g. tumours that appear not to contain fat) should be investigated with CT or MRI as these scans provide more detail
  • Blood pressure should be checked yearly. High blood pressure, or hypertension, can accelerate a loss of kidney function.
  • Blood tests should be done yearly if there are large or multiple lesions to find out how well the kidneys are working
  • People with TSC should aim for a healthy diet and lifestyle to ease the burden on the kidneys and avoid high blood pressure

People with AMLs should be aware of the type of symptoms that are associated with bleeding from the AMLs. This includes back or abdominal pain, nausea, vomiting and dark or blood stained urine.

Treatment

Angiomyolipomas (AMLs) are usually only treated if they are very large or if there has been bleeding. Treatment should try to preserve the surrounding kidney. Treatment options include:

  • Angiography and embolisation: this process blocks the blood vessels that supply the AML and therefore stops bleeding and causes the AML to shrink.
  • Surgery: The AML can be removed. In some cases a whole kidney will have to be removed but this should be avoided if possible. A very small number of people with TSC have had kidney transplants.
  • mTOR inhibitors: There is some evidence from clinical trials that these new medicines may slow growth or even shrink AMLs in some people with TSC.

 

About this article

Prepared by: Clare Stuart, The Australasian Tuberous Sclerosis Society

Reviewed by: Dr Sean Kennedy, Paediatric Nephrologist, Sydney Children’s Hospital

References:

  1. Kwiatkowski D.J., Whittemore V.H. & Thiele E.A. (2010) Tuberous Sclerosis Complex: Genes, Clinical Features, and Therapeutics. Weinheim: Wiley-Blackwell
  2. Renal Manifestations in TSC, Tuberous Sclerosis Alliance, viewed 30th March 2012, http://tsalliance.org/pages.aspx?content=598.
Parts of this web page have been adapted with permission from copyrighted content developed by the Tuberous Sclerosis Alliance,  www.tsalliance.org.