[Lithium clearance in polycystic kidney disease].

Disorders of tubular transport of sodium are thought to be involved in pathogenesis of cyst formation and development of hypertension in autosomal dominant polycystic kidney disease (ADPKD). Recently lithium has been proposed as a quantitative marker of proximal tubular reabsorption of sodium and lithium clearance as a method to analyze tubular sodium handling. To evaluate tubular sodium handling in early stage of ADPKD, lithium clearance (600 mg of Lithium carbonicum p.o.) was performed in a control group of pts. with ADPKD and normal glomerular filtration rate (n = 28), age 19.9 +/- 8.8 years) and in a control group of healthy volunteers (n = 43), age 30.3 +/- 9.0 years). Both groups did not differ in plasma or urine concentrations of electrolytes; plasma creatinine levels were slightly higher in ADPKD group than in controls (83.4 +/0 18.0 mumol/l vs. 93.4 +/- 24.2 mumol/l, p < 0.05). We did not demonstrate any statistically significant difference between the group of ADPKD and control group in lithium clearance and in fraction excretion of lithium (23.6 +/- 14.5 vs. 19.5 +/- 8.7 ml/min, resp. 15.3 +/- 8.8 vs 13.8 +/- 7.8%). Nor proximal tubular resorption of sodium, neither distal tubular resorption of sodium did differ between the group of ADPKD and control group (86.18 +/- 2.2 vs 84.7 +/- 1.80% resp. 94.7 +/- 2.6 vs. 94.5 +/- 3.6%). When comparing parameters of sodium handling between pts. with ADPKD and hypertension (6/28) and pts. with ADPKD without hypertension no difference was found. In conclusion, we could not demonstrate any statistically significant difference in tubular handling of sodium, when based on lithium clearance between the groups of ADPKD with normal glomerular filtration rate and control group.