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Does Cystic fibrosis predispose to the urolithiasis occurrence ? Do patients with cystic fibrosis present urolithiasis more frequently than another people? If yes, what is the explanation?
Dear questioner

Cystic fibrosis predisposes to the occurrence of urolithiasis composed principally of oxalate. The frequency of the occurence of lithiasis is increased for cystic fibrosis patients with an increase in frequency from 3.5 to 5,7%.
The composition of urine is abnormal in case of cystic fibrosis, even without lithiasis. Notably, there is more oxalate and some patients present urinary oxalate crystals even if there is no lithiasis.
In addition, a study found that 50% of cystic fibrosis patients with transplanted lung who had had a kidney biopsy because of renal failure, presented oxalate deposits in their biopsy.

The increase of the oxalate rate in the urine is the consequence of several elements :
- digestive malabsorption increases oxalate absorption
- a bacterium (Oxalobacter formigenes) which is normally present in the intestinal flora and damages oxalate, is susceptible to antibiotics as ceftazidime and cotrimoxazole. So, antibiotic treatment which damages this bacterium leads to an increased oxalate rate.
- these two antibiotics play also a role in modifying the kidney calcium and phosphate absorption. CFTR abnormalities do the same modifications. So there is a increased calcium rate in the urine.
The increase of calcium and oxalate in the urine leads to their precipitation in the urine and to the formation of urolithiasis.

Sincerely yours
Dr Isabelle Danner-Boucher
14.7.2011 Please see more information on this in the follow-up question: "Urolithiasis: how to avoid it?"[showitem]=1365&tx_expertadvice_pi1[search]=

D. d'Alquen