Evidence for preservation of cortical bone mineral density in patients on continuous ambulatory peritoneal dialysis

Abstract

It is still unclear whether dialysis modality, i.e., continuous ambulatory peritoneal dialysis (CAPD) versus hemodialysis (HD) specifically affects bone mineral density (BMD). To answer this question, 34 patients on HD and 25 on CAPD were matched for age, sex, height, and body weight with 125 normal subjects. BMD was measured using dual-energy X-ray absorptiometry (DXA; Hologic QDR 1000/W) at the lumbar spine (trabecular bone), the femoral neck (mixed cortical and trabecular bone), the distal tibial diaphysis (cortical bone), and the epiphysis (trabecular bone) in all subjects. No significant difference for blood hemoglobin, albumin, total and ionized calcium, intact parathyroid hormone (PTH) or phosphorus concentrations, as well as for alkaline phosphatase activity, failed renal allograft, prior steroid therapy, prior parathyroidectomy, duration of uremia, or of dialysis was found between patients on HD and those on CAPD. However, the residual daily urine volume and renal function at the time of the absorptiometry were higher in CAPD than in HD patients (p < 0.05) as well as the mean dialysate calcium concentration during dialysis, the blood bicarbonate concentration, and the residual renal function at the initiation of dialysis (p < 0.01, p < 0.05, and p < 0.005, respectively). In contrast, the total dose of calcium carbonate was lower in CAPD than in HD patients (p < 0.01). Results of BMD were expressed as Z scores (the number of standard deviations from the appropriate mean of BMD of 623 healthy subjects adjusted for age and sex). At the lumbar spine, no significant difference with respect to BMD was observed between the three groups. At the femoral neck and tibial epiphysis, HD patients had lower BMD (p < 0.001) than normal controls, whereas no difference was observed between HD and CAPD patients. At tibial diaphysis, patients on HD had lower BMD (p < 0.001) than patients on CAPD and than normal controls, with the values being similar in patients on CAPD and in normal controls. The results remained identical after exact matching of HD (n = 25) and CAPD (n = 25) patients for dialysis duration (1.9 +/- 0.3 and 1.7 +/- 0.3 years, respectively). Multiple regression analysis revealed significant negative correlations between Z scores at the lumbar spine (p < 0.05), femoral neck (p < 0.02), tibial diaphysis (p < 0.005), and tibial epiphysis (p < 0.05) on the one hand and plasma alkaline phosphatase activity on the other. The Z score at tibial diaphysis was also correlated with residual renal function at the initiation of dialysis (p < 0.05). In conclusion, this study provides evidence for the preservation of cortical bone with CAPD as opposed to HD. The higher residual renal function observed in the former treatment modality might account, at least in part, for this finding.

Bone mineral density in patients on maintenance dialysis

“…Despite of the higher prevalence of ABD in PD, other authors reported no difference in PTH levels between PD and HD patients [60,[87][88][89]. Increased resistance of bone to PTH in patients on PD compared to HD could explain this finding.…”

“…In earlier papers, it was proposed that PD has favorable influence on bone mineral density compared to hemodialysis [33, 86,87]. In contrast to intermittent hemodialysis, peritoneal dialysis is a continuous therapy providing constant control of electrolytes and bicarbonate (or lactate) delivery that is probably beneficial for the bone.…”

“…In an earlier study by Mottet et al [87], BMD of patients on hemodialysis (HD), peritoneal dialysis (PD) and healthy controls were compared. Patients were matched for age, gender, height, weight and there was no difference in ALP and PTH levels.…”

Review article: Bone density in patients with chronic kidney disease stages 4‐5

“…Figure 1 shows the average values of BMD in studies of patients with CKD Stage 5D 4–6,12,13,16,29–76 . These values are expressed as Z ‐scores, which compare BMD in the patients with the BMD from the reference values of age‐ and gender‐matched persons in the community.…”

Tibial or hip BMD predict clinical fracture risk equally well: results from a prospective study in 700 elderly Swiss women

“…In patients with metabolic bone diseases, such as hyperparathyroidism, cortical bone loss is known to be more pronounced than trabecular bone loss [15][16] and these patients are at increased risk for fractures [17]. In dialysed renal insufficiency patients, earlier research has provided evidence for the preservation of cortical bone (measured at T-DIA) with continuous ambulatory peritoneal dialysis compared to haemodialysis, possibly in relationship with the higher residual renal function observed in the former [18]. Furthermore, in the very specific population of female to male transsexuals under long-term hormonal treatment, the effect of androgens on cortical bone was shown in a crosssectional study measuring BMD at the tibial sites [10].…”