The clinical course of 66 boys and 49 girls with autosomal recessive polycystic kidney disease recruited from departments of paediatric nephrology was investigated over a mean observation period of 4.92 years. This is a selected study group of children from departments of paediatric nephrology who in most cases survived the neonatal period, since birth clinics did not participate. The median age at diagnosis was 29 days (prenatal to 14.5 years). We observed decreased glomerular filtration rates (GFRs) in 72% (median age at onset of decrease of GFR < 2 SD, 0.6 years; range, 0-18.7 years), and 11 patients developed end-stage renal disease. Hypertension requiring drug treatment was found in 70% (median age at start of medication, 0.5 years; range, 0-16.7 years). Kidney length was above the 97th centile in 68% of patients, and kidney length did not increase with age or deterioration of renal function. Urinary tract infections occurred in 30%, growth retardation in 25%, and clinical signs of hepatic fibrosis were detected in 46%. Thirteen patients (11%) died during the observation period, 10 of them in the first year of life. There was a statistically significant sex difference in terms of a more pronounced progression in girls. The survival probability at 1 year was 94% for male patients and 82% for female patients (p < 0.05) in this study. Urinary tract infections occurred more frequently in girls (p < 0.025) and were observed earlier. In addition, more girls had impaired renal function, developed end-stage renal disease and showed growth retardation; these differences, however, were not significant. For the children in this study, however, our results indicate that the long-term prognosis in the majority of cases is better throughout childhood and youth than often stated.

Phosphate dialytic removal (PDR) depends in part on the type (acetate or bicarbonate) and the concentration of the buffer dialysate. Plasma phosphate reduction or PDR during a dialysis treatment is the algebraic sum, of phosphate cellular flux (removal or captation) and of phosphate tissular precipitation. High bicarbonate levels induce an intracellular shift of phosphate, thus not available for dialytic removal. On the contrary, acidosis prevents P shifting into the intracellular space, thus more P is available for dialytic removal. In order to evaluate cellular phosphate sequestration (CPS) we tested PDR in a crossover study. Three children were dialyzed (18 sessions) successively using either biofiltration with free buffer dialysate and a constant bicarbonate fluid infusion rate (BF) or using sequential biofiltration (SBF) with an initial controlled acidosis period realized by bicarbonate reinjection fluid rate modelling. PDR was higher in SBF (32 ± 4 mmol/session) than in BF (24 ± 6 mmol/session). SBF seemed to be efficient against CPS; it clearly demonstrates that bicarbonate modelling is a promising dialytic approach to enhance PDR. The real clinical relevance of these biological results needs clinical long-term evaluation.

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Efficiency of peritoneal dialysis (PD) is dependent on adequate ultrafiltration (UF) and purification (solute clearance). These two goals apparently seem to conflict in terms of duration of dwells: short dwell time enhances UF capacity and, conversely, long dwell time enhances solute clearance. Peritoneal equilibration test (PET) allows an approach to the ultrafiltration time: the point at which the over time dialysate urea saturation and glucose desaturation curves cross, called APEX time. PET also allows an approach to the purification time: the point at which dialysate-to-plasma (DIP) concentration ratios over time are high. Because of the value of phosphate as a uremic factor of morbidity, we have chosen the time at which DIP phosphate is equal to 0.6 as a purification phosphate dwell time (PPT). A total of 17 patients were studied, over a five-year period, allowing 142 determinations. APEX times (range 18 71 min) and PPT (range 105 -238 min) were spread over a wide distribution. PPT and APEX times were significantly shorter in children younger than three years of age than in children older than ten years of age. PPT were nearly four times longer than APEX times. Knowledge of these conflicting ultrafiltration and purification times should help, in our view, in the individual choice of the PD modality: if UF is the major goal, short dwell times should be used (automated PD); if purification is the major goal, long dwell times should be used, as in continuous ambulatory peritoneal dialysis; if both are the target goal, tidal PD should be discussed.

Sequential hypertonic dialysis (SHD) was studied in two binephrectomized children over a period of 6 weeks. Each dialysis session comprised four periods of 45 min. The concentration of sodium in the dialysate [Na(D)] during the first period was 190 mmol/l and during the second period 140 mmol/l. The sequence was then repeated. The sodium-free water clearance [C(ONa)] was calculated from the measurements of the ultrafiltrate clearance and of the sodium clearance. Despite the short periods of hypertonic dialysis, C(ONa) was positive, suggesting that water was removed from the intracellular compartment as well as from the extracellular fluid. The transfer of fluid from the intracellular space improved circulatory stability during rapid removal of large volumes of fluid by ultrafiltration. SHD was also associated with increased removal of potassium and phosphate. Comparison of clinical parameters before and during SHD showed a tendency towards increased sodium balance and the possibility of raised cardiovascular morbidity. SHD stabilized blood volume during ultrafiltration, encouraging removal of uraemic toxins. SHD with this level of Na(D) is only a study dialysis method.