Effects of Continuous Ambulatory Peritoneal Dialysis (CAPD) on Renal Osteodystrophy

Abstract

The authors performed a metabolic and morphologic investigation of calcium metabolism in 22 patients on continuous ambulatory peritoneal dialysis (CAPD), selected as the first procedure. The patients were kept on a diet containing about 30 Kcal/ kg, 1 g/kg of protein, 950 mg of phosphate and 1500 mg of calcium per day. They showed normal mean values of serum calcium, phosphate, alkaline phosphatase, total protein and albumin at the start and after six, 12 and 21 months of CAPD. Serum PTH levels showed a progressive decrease over 21 months. Serum 25-OH-D3 were low at start and showed a further decrease after 12 months of CAPD. Before and during CAPD, serum 1,25 (OH)2D3 levels were undetectable. The bone mineral content was within normal range at start and showed a slight decrease after 12 months of CAPD. In 64% of the patients, bone biopsies, obtained from the iliac crest at the start showed osteomalacia, either isolated or associated with hyperparathyroidism. After 12 months, osteomalacia was still evident in 71% of this group. The authors concluded that dietary restriction of phosphate is important in preventing secondary hyperparathyroidism in patients on CAPD. However, prevalence of osteomalacia is due to defective vitamin D metabolism and its management requires administration of vitamin D metabolites.

In its morphological aspects and clinical features, renal osteodystrophy (RO) may differ significantly between patients on CAPD and those on hemodialysis (1–3). In addition, workers have reported conflicting opinions concerning the incidence and severity of bone lesions in CAPD patients (4–6). We undertook this investigation in order to evaluate the evolution and clinical, biochemical and morphologic aspects of RO in 22 ESRD patients treated with CAPD after long-term restriction of dietary protein and phosphate.