Nephrolithiasis, renal handling

EVIDENCE OF ABNORMAL RENAL HANDLING OF URIC ACID IN PATIENTS WITH NEPHROLITHIASIS AND HYPERURICOSURIA... 

A group of patients forming calcium oxalate stones are hyperuri-cosuric and it is thought that their excessive urate excretion contributes to calcium-stones formationl. The pathomechanisms invoked are dietary purine excess and endogenous uric acid overproduction, being defective tubular reabsorption of urate "unattractive because uricemia was found to be normal in patients with recurrent calcium nephrolithiasis (RCN) and hyperuricosuria. Current studies were undertaken to define the incidence, role of diet, abnormalities of the renal handling of urate, and associated metabolic disturban-c"es in patients with RCN and hyperuricosuria. 

Fifty patients (22 males and 28 females mean age 46 years) were consecutively referred to our Metabolic Unit for the evaluation of recurrent nephrolithiasis. Diagnosis was made on the basis of spontaneous emission or chirurgical extraction of two or more calculi with an interval superior to one year. In every patient we performed a metabolic study and the results were compared with those obtained in 20 controls (10 males and 10 females mean age 33 years) Hyperuricosuria was defined as daily uric acid excretion above 800 mg for men and 750 mg for woman, while on a purine-free diet. Renal handling of uric acid ms evaluated by means of pyrazinamide (PZA) and probenecid (PB) tests. ... 

The clinical manifestations of gout, i.e. articular and renal disease, are intimately connected with hyperuricemia and/or particularities of renal handling of uric acid. It is well established that normalization of plasma uric levels will cure the joint disease. The diminution of renal uric acid excretion by administration of allopurinol will cure nephrolithiasis in its uncomplicated forms. One may presume that the other manifestations of the gouty kidney (i.e. parenchymal renal disease, hypertension and azotemia) will also be influenced by a therapy reducing urinary uric acid however no reliable reports exist as yet on this point. 

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