CF and kidney disease

Question

I would like to know what is known about kidney disease and CF. My daughter of 37 has CF and recently started on dialysis as well. She has a mild form of diabetes, injects 4IU per meal but has serious diabetic complaints. At first it was a mystery; she has been unexplainable very ill. Everything has been searched for, but without success. According to the nephrologist there are 4 patients in Australia with exactly the same complaints but mild or no diabetes at all. My question is whether there are more CF patients in the world with serious kidney disease; and is there any research in this field ?

Answer

Dear parents,

Cystic fibrosis is caused by a gene defect that results in a poor function of the CFTR channel, a chloride channel present in the epithelia of our body. Although this CFTR chloride channel does not function optimally in the epithelium of the kidney in CF, in general, people with CF suffer very little kidney problems by the disease itself. This in contrast with disease in the lungs and the pancreas. The only consistent finding in patients with CF is some extra loss of small proteins via the kidney. This however does not harm the kidney function in any way. Also careful exploration in animals confirms that the function of the CFTR channel is not essential for optimal kidney function. The CFTR channel could however play a role in diseases such as polycystic kidneys, but is not linked to CF.
This however does not mean that patients with CF cannot have any kidney problems. Indeed in some instances the kidney function is impaired.

CF patients are frequently treated with antibiotics for lung infection with Pseudomonas aeruginosa. Some antibiotics administered via the blood (especially colomycin and aminoglycocides such as tobramycin and amikacin) have the potential of damaging the kidney. Treatment with these antibiotics rarely causes problems if the dose of the antibiotic given is carefully monitored (measured in the blood) and if the doses are adjusted appropriately. Kidney damage usually only occures when antibiotics have been given for a long time or very frequently. The administration of these same antibiotics via inhalation (aerosol) does not cause kidney damage because the amount reaching the blood is minimal. The simultaneous administration of other medication that is potentially toxic to the kidney such as ibuprofen, diuretics or immunosuppressive medication (post lung transplant) can facilitate worsening of kidney function. Also diabetes related to cystic fibrosis can lead to some kidney damage.

Patients with CF have an increased chance of having kidney stones. This is not related to poor kidney function but probably to an increased amount of oxylate excreted via the urine.

There are a few recent reports on a specific kidney disease in patients with CF i.e. membranoproliferative glomerulonefritis. The exact link with CF is uncertain (coincidence or not ?) and the chance of CF patients to have this kidney disease is very low.

Of course, patients with CF can also ‘by chance’ still suffer from another disease than CF.

To come back to your original request, there are indeed in the world, other patients with cystic fibrosis and serious kidney problems. Research about CF is extensive and includes research to get a better picture on how often serious kidney problems occur in patients with CF and to define better strategies to make sure antibiotics do not cause any kidney damage. We suggest that you discuss with your CF doctor and with your kidney doctor which of the causes we enumerated is the most likely cause of the serious kidney problems in your daughter.

We wish you and your daughter the best and hope that this answer somewhat enlightens you on the topic of kidney disease and CF.


L. Dupont, K. De Boeck, M. Proesmans, F. Vermeulen

27.11.2008