Renal gravel

Question

Dear expert team,

my 7-year-old son has CF (F508 homozygous), his current FEV1 is at 88.4% and he is being treated with antibiotics continuously (cephalexin 1000mg and ciprofloxacin 250mg – 3 weeks on/3 weeks off, as well as colistin). We do an i.v. therapy at home once every year, the last one ended in mid-February. Pseudomondas was last detected in January 2008, but never again since.

Now he had a kidney stone/renal gravel discharge, which was obviously very painful for him… (No abnormalities in the blood count.) My question now is: is it possible at all that this is linked to the drugs? Is the long-term antibiosis really necessary?

Thank you for your answer.

Answer

Hello,

Kidney stones and/or renal gravel are rather common in CF. There are many reasons for their emergence. Apart from malnutrition, composition of the diet (e.g. meals rich in oxalate), or protein content of the food, a shift of substances that are excreted via the kidneys (uric acid, oxalate, calcium, citrate) can cause kidney stones. In CF, there is a particularly increased risk for the emergence of calcium and oxalate stones. In addition, the typically low amount of urine in CF patients can contribute to the formation of kidney stones.

The long-term administration of antibiotics changes the intestinal flora and, for instance, reduces the number of bacteria that degrade oxalic acid, which increases the probability of hyperoxaluria and hence of the emergence of kidney stones. A link to the drugs you mention cannot be ruled out. I assume your son was prescribed a 3-week-on, 3-week-off therapy with ciprofloxacin in order to minimize side effects and possible resistances. Ciprofloxacin is excreted primarily via the kidneys and can lead to excretion of crystals. At any rate, a detailed diagnostic assessment concerning other causes and the risk of kidney stone formation is advisable.

Concerning antibiotics therapy and this new knowledge about kidney stone formation, I suggest you discuss the long-term therapy and possible alternatives with your doctor again. Of course, this depends on the germ colonization and the frequency of examinations (positive sputum analyses).

Kind regards
Dr. H. Ellemunter

08.05.2012