Magnesium supplementation to prevent recurrence of renal stones

Abstract

The filtered Mg is reabsorbed by the renal tubules: 10-25% in the proximal tubule, 60-70% in the thick ascending limb (TAL) and 5% in the distal tubule. Transport of Mg in TAL is primarily passive (moving from the lumen to the interstitium) via the paracellular channels, due to a transepithelial gradient generated by the apical NaK2Cl cotransporter (Figure 1). ABSTRACT Stone formers have lower urinary magnesium than healthy people. Higher urinary magnesium levels are associated with lower incidence of kidney stones, and hypomagnesuria has been described as a lithogenic risk factor. Magnesium can have direct and indirect inhibitory effects on lithogenesis: decreasing the absorption of oxalates in the intestine; forming magnesium oxalate complexes which reduces the saturation of calcium oxalate; increasing the urinary citrate and inhibiting the conversion of the calcium oxalate in its monohydrated form. Oral supplementation with magnesium is an effective way to correct hypomagnesuria. However, oral magnesium supplementation in recurrent stone formers with hypomagnesuria is still a subject of ongoing debate, and physicians treating these patients underestimate its potential preventive effects. Oral magnesium supplementation can be used as an adjuvant therapy to the standard prophylactic therapy, mainly in association with an alkali salt. It is well tolerated and has few adverse effects.