Calcium balance in peritoneal dialysis patients treated by continuous ambulatory peritoneal dialysis (CAPD) and automated peritoneal dialysis (APD) cyclers.

INTRODUCTION: Although vascular calcification is a recognised complication for haemodialysis patients, peritoneal dialysis (PD) patients are also at risk. As such we wished to review peritoneal and urinary calcium balance and the effect of calcium containing phosphate binders (CCPBs).

METHODS: Twenty-four-hour peritoneal calcium balance and urinary calcium were reviewed in PD patients undergoing their first assessment of peritoneal membrane function.

RESULTS: Results from 183 patients, 56.3% male, 30.1% diabetic, mean age 59.4 ± 16.4 years, median 2.0 (2-6) months of PD, 29% treated by automated PD (APD), 26.8% continuous ambulatory (CAPD) and 44.2% APD with a day-time exchange (CCPD) were reviewed. Peritoneal calcium balance was positive in 42.6%, and remained positive in 21.3% after including urinary calcium losses. PD calcium balance was negatively associated with ultrafiltration (odds ratio 0.99 (95% confidence limits 0.98-0.99), p = 0.005. PD calcium balance was lowest with APD (APD - 0.45 (- 0.78 to 0.05) vs CAPD - 0.14 (- 1.18 to 0.59) vs CCPD - 0.03) - 0.48 to 0.5) mmol/day), p < 0.05, with 82.1% of patients with a positive balance prescribed icodextrin, when combining peritoneal and urinary losses. When considering CCPB prescription, then 97.8% of subjects prescribed CCPD had an over-all positive calcium balance.

DISCUSSION: Over 40% of PD patients had a positive peritoneal calcium balance. Elemental calcium intake from CCPB had a major effect on calcium balance, as median combined peritoneal and urinary calcium losses were < 0.7 mmol/day (26 mg), so caution is required to prevent excessive CCPB prescribing, increasing the exchangeable calcium pool and thus potentially increasing vascular calcification, particularly for anuric patients.