Disorders of bone and mineral metabolism affect almost all patients with advanced chronic kidney disease with high prevalence of decreased bone mineral density (BMD). BMD is negatively correlated with vascular calcification and cardiovascular risk in CKD pts. and both conditions are strongly associated with higher mortality. However in these patients fractures are common by impairments in bone quantity and quality and by abnormalities of neuromuscolar function. Aim of the study is to confirm these observations in chronic peritoneal dialisys patients.
Materials and Methods
We studied 45 PD patients, 36 in CAPD and 9 in APD (mean age 61,9 ±14,5 y, 41,3% Women and 58,7% Man, mean age Man 65,7±11 Years, Women 56,2±17 Years p=0,031 for sex) mean duration of PD was 21,9±25,4 months. Causes of end stage renal disease: Glomerulonephritis 13 patients, Chronic Pielonephritis 5 patients, Hypertension 10 patients, Autosomal Dominant Policistic Kidney Disease 9 patients, Diabetes 8 patients. These patients underwent an abdominal computed tomography scan. The severity score for Abdominal Aortic Calcifications (AAC) were: 1=none, 2=mild, 3=moderate, 4=severe. For each patient we collected the following laboratory data: calcium corrected for albumin, PTH, phosphorus, alkaline phosphatase, haemoglobin, BMI, diuresys, KT/V, use of Vitamin D, Cinacalcet, phosphate binders, Eritropoietin stimulating agents, warfarin (Table 1, 2). Quantitative CT mesaurements of BMD (mg/ml) using fully automated software were obtained at the first, second, third and fourth lumbar vertebrae. T and Z score were calculated by comparing with normal control data. Statistical analisys performed with SPSS.
In the 45 patients included in the study, the mean lumbar spine T score was –3,52±1,33, the lumbar Z spine Z score was –0,25±0,99. According to the criteria based on lumbar spine T scores, 55% of 45 patients were osteoporotic, 28% had osteopenia and 17% had lumbar spine T scores within the normal range.We found a positive correlation between low BMD and age (M p<0,006, r=-0,516, W p<0,001, r=-0,763) and BMD and calcium in women (p=0,037, r=0,481). 25 pts (55,6% M and 42,1% W with no statistically significant difference between the sexes) were osteoporotic (BMD <160 mg/ml), and respectively 14 and 11 of theme showed severe and mild AAC. After 2 years the overall prevalence of fracture was 15,5% (7 pts). 12 pts (26%) died. All the pts died and those with fracture showed a low BMD and a severe AAC. No correlations was found between laboratory data, BMI, diuresys, KT/V, use of medications, lenght of dialisys and BMD-AOC.
Our results indicated that, considering their CT- based BMD values, 83% of chronic PD patients have subnormal bone mass –55% within the osteoporotic range and 28% within the osteopenic range. Our findings also confirm that low BMD is correlated with age, vascular valcifications and cardiovascular risk as in CKD patients. We agree with other Authors that low BMD might constitute another nontraditional risk factor for cardiovascular disease in CKD and in PD patients. We could not confirm the findings of other Authors who suggested that low body weight and low KT/V were the most important risk factors for low BMD in PD patients.