Urolitiasis

Metabolismo de la Urolitiasis. Estudio metabólico

Hypercalciuria

Hyperoxaluria

Hyperuricosuria and Gouty Diathesis

Hypocitraturia

Struvite and Staghorn Calculi

eMedicine

"urolithiasis/metabolism"[MeSH Major Topic] :

Urinary citrate and renal stone disease: the preventive role of alkali citrate treatment.

Related Articles

Urinary citrate and renal stone disease: the preventive role of alkali citrate treatment.

Arch Ital Urol Androl. 2009 Sep;81(3):182-7

Authors: Caudarella R, Vescini F

Hypocitraturia or low urinary citrate excretion is a common feature in patients with nephrolithiasis, particularly in those with calcium stone disease. Citrate is a weak acid that is synthesized inside Krebs' cycle. It can also enter the body through dietary intake. Differences in intestinal handling, serum concentration as well as filtered load of citrate were not found between kidney stone formers and normal subjects. On the contrary, several metabolic abnormalities, such as metabolic acidosis, hypokalemia and starving, seem to influence the renal handling of citrate by inducing a decrease in the urinary citrate excretion. Hypocitraturia is defined as urinary citrate excretion lower than 320 mg/day. Literature data show a large prevalence of hypocitraturia in patients with nephrolithiasis, ranging from 8% up to 68.3%. The protective role of citrate is linked to several mechanisms; in fact citrate reduces urinary supersaturation of calcium salts by forming soluble complexes with calcium ions and by inhibiting crystal growth and aggregation. Furthermore, citrate increases the activity of some macromolecules in the urine (eg. Tamm-Horsfall protein) that inhibit calcium oxalate aggregation. Citrate seems able to reduce the expression of urinary osteopontin. A role of citrate in pathogenesis of metabolic bone diseases has been recently suggested and citrate measurement in urine has been proposed as a predictor of both bone mass loss and fracture risk. Idiopathic calcium stone disease, with or without hypocitraturia, can be treated with alkaline citrate, as well as other forms of nephrolithiasis and different pathological conditions. The therapy with potassium citrate, or magnesium potassium citrate, is commonly prescribed in clinical practice in order to increase urinary citrate and to reduce stone formation rates. Our data as well as those of the literature confirm that alkali citrate induces both an increase of protective urinay analytes (eg. citrate, potassium and pH) and a decrease of calcium oxalate supersaturation. Moreover, alkali treatment reduces the rate of stone recurrence and increases the clearance rates and dissolution of stone fragments. Last but not the least, an increasing number of papers pointed out the protective role of alkali citrate in preserving bone mass in stone formers as well as in healthy subjects with bone loss. Nevertheless, the evaluation of urinary citrate in patients with kidney stones and the treatment of these patients with alkali salts namely with potassium citrate are still scarce.

PMID: 19911682 [PubMed - indexed for MEDLINE]

Risk factors for renal calcium stone formation in South African and European young adults.

Arch Ital Urol Androl. 2009 Sep;81(3):171-4

Authors: Rodgers A, Allie-Hamdulay S, Pinnock D, Baretta G, Trinchieri A

OBJECTIVES: The different susceptibility to renal stone disease of white and black people has been previously explained in terms of intrinsic (genetics) and extrinsic (diet, lifestyle) factors. However, in South Africa, the absence of stone disease in the black population has not yet been fully explained by either of these. The aim of the present study was to identify potential differences between black and white subjects in South Africa and white subjects in Europe with respect to their relative dietary and urinary risk factors for renal stone formation. MATERIALS AND METHODS: A total of 72 healthy subjects (45 males and 27 females, age range 21-30 years) with no previous history of renal stone disease or specific diseases predisposing to renal stone formation were recruited in South Africa (SA) and in Italy (IT). They were divided in three groups: South African blacks (SA-B), South African whites (SA-W) and Italian whites (IT-W). Each participant provided a 24-hour dietary record and 24-hour urine sample taken over the same period. Nutrients and calories were calculated by means of food composition tables using a computerised procedure. Urinary concentrations of potassium, sodium, calcium, phosphate, oxalate, urate, citrate, magnesium, and creatinine, together with the pH and urinary volumes, were measured. RESULTS: The mean carbohydrate intake was significantly higher in SA-B (293+90 g/day) than in both SA-W (194+74, p = 0.002) and IT-W (212 +/- 81; p = 0.000). Daily magnesium intake was higher in SA-B (290+124 mg/day) than in IT-W (176+73 mg/day, p = 0.002). The mean daily urinary excretion of calcium was significantly (p = 0.029) lower in SA-B (3.07 +/- 1.68 mmol/day) with respect to SA-W (4.65 +/- 2.44 mmol/day) and IT-W (4.51 +/- 1.89 mmol/day) whereas mean daily urinary excretion of citrate was significantly (P = 0.012) higher in SA-B (3.36 +/- 1.4 mmol/day) than in SA-W (3.09 +/- 1.45 mmol/day) and IT-W (2.36 +/- 0.98 mmol/day). CONCLUSION: Although the carbohydrate intake and the percent of energy from carbohydrate of black subjects in this study were higher with respect to white controls, we were not able to show any other relevant difference of the known dietary stone risk patterns between black and white subjects. On the other hand the urinary patterns of black controls seem to be more favourable in term of risk for stone formation than those of white controls showing a lower calcium excretion and a higher citrate excretion in the urine. Our result of higher carbohydrate intake in black subjects is counter-intuitive as it suggests a higher risk of stone formation in this group. This puzzling result may have arisen because our subjects were recruited from the urban population rather than from rural areas, suggesting that western diets and lifestyles may ultimately change the stone incidence profile in the black population.

PMID: 19911680 [PubMed - indexed for MEDLINE]