By Yolanda Smith, BPharm
Cystinuria is a chronic condition that cannot be cured, although certain management techniques can help to prevent the formation of stones in the kidneys and resulting complications.
Firstly, it is important to make small lifestyle changes to prevent kidney stone formation and the need for further therapy.
Keeping hydrated by drinking an adequate amount of water can help to lower the concentration of cystine in the urine. As a result of the reduced cystine concentration, there is a decreased risk of formation of stones. Research in this area has indicated that nearly one-third of patients can prevent stone recurrence by simply increasing fluid intake.
Additionally, small dietary changes can have a significant impact on the formation of kidney stones. In particular, reducing the consumption of salt has been associated with decreased risk of stone recurrence.
The pH is an important factor for kidney stones to form, as cystine is more soluble at a higher pH. For this reason, alkalinizing agents like potassium citrate can help to increase the pH and the solubility of cystine, resulting in fewer recurrences.
Chelation or Antiurolithic Therapy
Thiol compounds have the ability to bind to cystine, forming a disulfide complex that does not cause the formation of stones and may help to dissolve kidney stones.
D-penicillamine is a chelating agent that increases the solubility of cystine, reducing the effects of cystinuria. Approximately half of all patients experience adverse reactions with this therapy, which limits their therapeutic use. These effects may include rash, gastrointestinal effects, arthralgia, leukopenia and nephritic syndrome. Tiopronin is another agent with similar action and side effect profile.
Alpha-mercaptopropionylglycine (alpha-MPG) is a second-generation chelating agent with a similar mechanism of action, but is generally tolerated better that C-penicillamine.
Captopril is an ACE inhibitor drug usually used to treat hypertension that forms a thiol-cystine mixed disulfide that has a higher solubility and can reduce the formation of stones. This is usually used a second-line therapy option when other treatments have failed to produce an adequate response.
When the stones in the urinary tract are large in size and cause significant pain, there may be need for their surgical removal to relieve symptoms. There are several different surgical procedures that may be performed, depending on the specific circumstances.
Extracorporeal shock wave lithotripsy (ESWL) uses shockwaves directed towards large stones to fragment the stones into smaller pieces that can pass through the ureters and be excreted more easily. However, this procedure is less effective for kidney stones associated with cystinuria than other types of stones.
Percutaneous nephrolithotomy involves the insertion of an instrument into the kidney that is used to break the stones or remove them from the organ entirely.
It is worth noting, however, that these surgical procedures will not help to prevent the formation of kidney stones in the future. They are effective to remove current stones and relieve the related symptoms, but other preventative techniques are required to prevent recurrence.
When making decisions about the best course of treatment for an individual with cystinuria, it is important to consider relevant factors. These may include the frequency and severity of symptoms, the response to treatment and the likelihood of symptom recurrence.
Follow-up management should involve monitoring of the urinary pH and cystine concentration in the urine. Patients with severe forms of the disease should have regular checkups every three months with ultrasound imaging to check for any changes. This also helps to improve patient compliance, which has a positive effect on overall health outcomes.
Last Updated: Jan 10, 2016