Biochemical characteristics of cyst fluid in undialysed patients with autosomal dominant poiycystic kidney disease

Summary: The biochemical composition of cyst fluid was analysed in 148 cysts obtained from 10 patients with autosomal dominant polycystic kidney disease (ADPKD). Serum creatinine levels ranged from 1.7 to 9.0 mg/dL. No patients were receiving renal replacement therapy. Aspirated cyst volume ranged from 4‐120 mL. There was no significant correlation between cyst volume and cyst sodium concentration ([Na]cyst). Cyst sodium concentration demonstrated a bimodal distribution pattern, with one peak from 10‐20 mEq/L and the other from 140‐150 mEq/L. the ratios of cyst fluid versus serum sodium concen tration ([Na]cyst/serum) were positively correlated with [C1]cyst/serum, while negatively correlated with [K]cyst/serum, [Ca]cyst/serum, [P]cyst/serum and [UA]cyst/serum. Based on the [Nalcyst/serum, the cysts were assigned to three types: proximal (0.8‐1.4), indeterminant (0.4–0.8) and distal (<0.4). the percentage of each type was 54.7, 19.6 and 25.7%, respectively. There were no significant differences in [Na]cyst/serum between the right and left kidney in individual patients. the concentrations of amino acids were higher in the distal type than in the proximal type. These results indicate the divergent function of the cyst‐lining epithelia in polycystic kidneys.