Q: Our son is a 30 year living and working away from home. He had a diseased kidney removed 20 years ago. At that time we were told that his remaining kidney was fine and that it was working at 75% capacity.
He recently dropped a bombshell on us by telling us that this kidney was now functioning at only 28% and that he has been suffering with recurring bouts of gout in his big toes for which his GP has prescribed Codeine to ease the pain. He has also been told that he need not worry about sticking to his diet any more.
We don't know how much he is not telling us and we certainly don't want to be seen as treating him as though he is still a child, but as parents we need to gain some understanding of how and when our son will be referred back into the renal care system, what his treatment might be and what we as a family can do to help him.
I am sure our situation is one that is being mirrored by many families in the UK. What in your opinion would be our best way forward.
A: Thank you for the question. Kidney disease affects individuals and families. As parents I am sure you are working hard to balance the independence and autonomy of your adult son with your natural concerns about the future. Having children of a similar age myself I hope I am permitted to say “your children remain your children”; they and your son might retort “parents never change”.
The gout your son has now developed is probably unrelated to the underlying kidney problem despite the fact kidney disease is linked to increased levels of urate. Precipitation of urate in the joint space, usually of the big toe, causes the attacks of gout and higher levels of urate increase the risk of an attack. Although urate levels rise as kidney function falls, gout itself is an unusual complication of chronic kidney disease. Rarely urate, which is excreted by the kidney, can crystallise in the urine and form kidney stones and there are some very unusual conditions where urate kidney stone disease is the main cause of kidney failure. They are uncommon and it is unlikely in your son. Much more of a worry when gout occurs in people with kidney disease is the risk that some of the medicines for gout can transiently or permanently reduce kidney function further. This is a particular risk when non-steroidal anti-inflammatory drugs, known as NSAIDS are used for protracted periods of time. Indomethicin, Ibuprofen and Voltarol are examples of NSAIDS. Some NSAIDS are available over the counter from high street pharmacists or supermarkets. People with kidney disease should always be careful about what medicines they take – both prescribed and over the counter. Codeine is a simple painkiller and doesn’t cause kidney damage but can accumulate when kidney function is very low. If the attacks of gout are frequent, a drug call Allopurinol can help prevent them. The dose does need to be reduced in chronic kidney disease and it is a drug that can interact with other medicines, so for instance, it shouldn’t be used with Azathioprine.
What was the cause of the damage to the kidney your son had removed aged 10? I am sure if it was cancer you would have said. Other reasons for removing a kidney are recurrent infection or severe scarring due to childhood reflux. The cause of the damage to that kidney and the reason for removing it might be very relevant to your son’s current situation. If for instance the cause of the damage was reflux and the reason for removal was control of blood pressure then avoidance and treatment of infections in the remaining kidney and management of hypertension would be key goals.
From what you say it sounds like your son’s remaining kidney wasn’t normal when the damaged kidney was removed. That would definitely be the case if it was only working 75% of what one would expect of a normal kidney. Indeed, in children and young people, if one kidney is damaged or removed, the other often grows to compensate and can do the work of one and a half kidneys. That also often happens after someone donates a kidney for transplantation.
On balance it seems likely that your son’s remaining kidney was already damaged by the time he was 10 years old. It is very likely that the current kidney function of 28% means your son’s estimated Glomerular Filtration Rate (eGFR – the measure of both kidneys function) is 28 mils per minute. Normally each kidney would provide 50 mils per minute. So one could think of your son’s single remaining kidney function of being 56% (or 28/50 x 2) of that expected by a single normal kidney. Even so, an estimated GFR of 28 mils per minute is low. It is Stage 4 kidney disease. There is a high risk of raised blood pressure and a definite risk of further progressive kidney damage. The strongest predictors of that risk are blood pressure, rate of change of kidney function over the last few years and the level of protein in the urine. If there is no protein in the urine or it’s very low then the chance of the future need for transplantation or dialysis is much less than if there is a lot of protein in the urine.
At this stage of kidney disease regular checks of kidney function, blood pressure and urine for protein are needed to optimise care. Blood pressure should be perfect, protein in the urine should be minimised by the use of ACE inhibitor drugs and any vascular risk factors – smoking, lack of exercise, obesity should be addressed. With an estimated GFR of 28 mils per minute other complications of kidney disease should also be monitored – anaemia, bone mineral disorders and acidosis. Some but not all people with this level of kidney function do need to try and change their diet but that needs to be determined on an individual case by case basis.
Why don’t you suggest your son has a look at NHS Choices to find out more about gout and kidney disease so that he can play a full part in reducing his future risks and managing his conditions. If you have a look as well it might help the discussions within the family.
Published in Kidney Life magazine in 2010
