The Effect of Cystine Level and Urinary PH on the Recurrence of Cystine Stones
Purpose Retrospective review of the medical therapy on pediatric patients with cystin stones as regards recurrence rates. Material and Methods 21 patients (12 boy, 9 girl) under follow-up with cystin stones were retrospectively evaluated. Median diagnosis age was 1 year old(range:1-16). Medical therapy was applied with 10 to 15 mg/kg a-mercaptopropionylglycine and 1 mEq./kg potassium citrate or Scholl solution following the initial treatment. Results Surgery was performed on 18 patients (percutaneous nephrolithotomy in 21 sessions on 13 patients, open on 8 patients); ESWL on 12 patients (in 2,7 sessions in the average). All patients received the same medical treatment stated above. Urinary pH levels increased (pretreatment/posttreatment urinary pH were from 6,0± 0.63 to 6.6± 0.59) and cystine levels decreased (from 885±1118 to 322±204mmol./mol. creatinine) after treatment. Being the control urinary pH over 6.5 was observed to be effective in the prevention of recurrences (p=0.02). Recurrence was seen in none of the patients with control urinary system levels under 150. Recurrence significantly lower in patients with control cystine levels under 150 when urinary pH was over 6.5 (p=0.044) (Table). In addition, while recurrence was seen in two patients out of six with high cystine levels and urinary pH over 7, recurrences were seen in six patients out of seven with lower pH values. Table. Effect of urinary pH>=6.5 when cystine levels are high (p=0.044) CYSTINE>150; URINARY pH CYSTINE>150; URINARY pH>=6,5 TOTAL NO RECURRENCE 0 5 5 RECCURENCE + 5 3 8 TOTAL 5 8 13 Conclusions Keeping the control urinary pH above 6.5 for the prevention of cystine stones appears to be effective even in patients with high cystine levels.