FAQs

One of the great things about our online mailing list is that fact that people can ask questions from other people who have experience. However this can lead to very similar questions being asked. We have put together a FAQ on Cystinuria to see if this helps:

Should amino acid supplements be taken?  Is mental retardation and short stature related to protein malabsorption?  Could asymptomatic cystinuric siblings have malabsorption of amino acids?

Dr Lisa Ruml answers:  While it is true that most cystinuric patients are unable to absorb some amino acids (cystine, lysine, arginine, and ornithine), there is not a problem with protein malnutrition. Amino acids are also absorbed in pairs, and cystinuric patients can absorb these amino acids when they are in the pair form or short chains. Thus, there is not a problem with protein deficiency and amino acid supplements are not necessary. There is also no good evidence that mental retardation is in any way associated with cystinuria; and the observation that cystinuric patients are shorter than the general population has not been substantiated.

Will a kidney transplant solve the problem?

Dr Lisa Ruml answers: Yes, if a cystinuric patient receives a kidney from a non-cystinuric donor, that kidney will function normally and will be able to reabsorb cystine from the urine. Unfortunately, a renal transplant is a major procedure with long-term consequences from the medications required to prevent rejection. It is, however, the only option in some instances, but the need for this drastic measure is not common.

Is there a decreased life span?

Dr Lisa Ruml answers: If a patient with cystinuria is able to prevent stones, or at least produce and pass stones without resulting in blockage of the urinary tract, there should be no cause for reduced life span. Many patients never develop renal insufficiency (poorly functioning kidneys), particularly if they are compliant with their fluid regimen. If kidney damage does not occur, and in the absence of other complicating medical problems, then life expectancy is the same as in someone without cystinuria. If the kidneys become chronically blocked, function may worsen; if they become chronically infected, they sometimes have to be removed. If patients do end up on dialysis or receive a transplant, then they may have complications of those procedures and perhaps not do well. Like any patient on dialysis or with a transplant, serious and sometimes fatal complications are more likely than in an otherwise healthy person.

Are we OK to eat tomatoes? I understand they are quite acidic.

Dr David Goldfarb answers: Tomatoes are OK. Fruits and vegetables lead to urinary alkalinization. Yes there is citric acid in tomatoes, which has NO NET EFFECT on urinary pH. The citrate part of citric acid is a base, and neutralizes the effect of the acid. That’s why there is no problem with Bicitra, as one example, containing citric acid even if the preparation is used for urinary alkalization. Who could give up tomatoes?

Does a low methionine diet really help?

Dr David Goldfarb answers: Protein ingestion leads to more urinary acid to excrete. Fruits and vegetables lead to alkalization. This may be a more important reason to restrict protein intake than limiting methionine intake. I agree that the benefit of diet in the long run is not well studied, in children or adults and that protein intake could be overcome by more water drinking and effective alkalization. But I’ve noted that some of you out there claim to have benefited from a more vegetarian diet and I would bet that the effect on urine pH is more important than the effect on cystine excretion.

Isn’t Captopril a diuretic and therefore something we should avoid?

Dr David Goldfarb answers: Captopril (brand name Capoten) is not really a diuretic, though it may increase urine output in some patients, especially with heart disease, and can potentiate the effect of some diuretics. It lowers blood pressure and has beneficial effects on the kidneys for people with decreased kidney function and a tendency to progressively lose kidney function (like diabetes), which most people with cystinuria don’t have. It also happens to have a sulfhydryl group, which combines with the sulfhydryl groups in cystine to help solubilize the latter. The literature on its benefit is very spotty, with claims both ways. It’s reasonable to use it though its effect is probably small and my own feeling is that urinary cystine levels should be measured to show the benefit or its not worth continuing. But if you think its helping continue it anyway! It is absolutely contraindicated in women who might conceive while taking it. It won’t affect your ability to conceive later, it just causes significant birth defects if you conceive while on it. Cough is a common side effect.

Should we avoid diuretics which could lead to damage to the kidneys?

Dr David Goldfarb answers: Diuretics are not drugs that to my mind “damage” the kidneys with time. They can be used safely for long term treatment of high blood pressure. They have some mild side effects, but thiazides, as an example, are a class of drugs that have been used safely by millions of people for high blood pressure and they are currently in the first line of recommended drugs for high blood pressure according to the authoritative Joint National Committee (JNC) VI.

I am a little concerned that these amino acids we don’t absorb are ‘essential’ amino acids. What are they ‘essential’ for?

Dr David Goldfarb answers: The diminished absorption of various amino acids in people with cystinuria does not lead to nutritional deficiencies. This is because the ability to absorb small peptides (small chains of 2 or 3 amino acids) is NOT impaired. Only single amino acids. Therefore someone with this defect in intestinal absorption will still absorb enough cystine, lysine, etc., in a different form, that then can be broken down to the single amino acids. Similarly, the loss of cystine and the other amino acids in the urine will not lead to deficiencies of them; it’s just not enough to lead to “negative” balance of them. There is no evidence that I know of that there are nutritional defects of any amino acids.

If we are not able to utilize certain minerals because we don’t absorb the amino acids, is there any point in taking supplements?

Dr David Goldfarb answers: Minerals, like zinc, are not amino acids, and absorption or utilization of them as far as I know, is not affected by cystinuria.

Could my slowness to conceive be anything to do with cystinuria and/or mineral deficiencies?

Dr David Goldfarb answers: I can’t think of any reason why.

There are many different makes and types of Lithotripsy machine ESWL, and I was wondering if there is a difference in the effectiveness of the machines.

Dr Mike Grasso answers: The Dornier is the most powerful lithotriptor but uses old technology x-ray imaging which makes it difficult to see cystine stones. We use the Storz SLX which uses ultrasound for localization and this is a plus for cystine. It is also very powerful – but as you all know cystine is tough to break in general.

What can I do about stones causing symptoms. There are several suggestions in the handbook.

Dr David Goldfarb answers: What to do about stones causing symptoms has definitely changed since the Handbook was written. For instance, it would be reasonable to recommend using NSAIDS (non-steroidal anti-inflammatory drugs) like ibuprofen rather than nothing. Though not tried in cystinuria specifically, good controlled trials have been done in calcium stone patients and shown the benefits in promoting passage without surgery of stones less than 1 cm in size for Flomax (tamulosin; usually used for prostate disease) and steroids and nifedipine (usually used for high blood pressure). Does increasing fluid intake help pass stones: I doubt it! No trials show this either.