Weighing the evidence for treatment of chronic kidney disease mineral and bone disorder

Cardiorenal syndrome type 4: From chronic kidney disease to cardiovascular impairment

Cardiorenal syndrome type 4 (CRS type 4), or chronic renocardiac syndrome, has been defined as "chronic abnormalities in renal function leading to cardiac disease" and recognizes the extreme burden of cardiovascular disease (CVD) risk in patients with chronic kidney disease (CKD). CKD is common and increasingly recognized as a risk factor for CVD. Even though the treatment for CVD has dramatically improved over the past decades, it still takes responsibility for up to 50% of deaths in CKD patients. For this reason, patients with CKD should be thoroughly evaluated for cardiovascular risk factors that require careful management, given the significant burden of CRS type 4 on the healthcare system. This review focuses on the most significant conventional and non-conventional CVD risk factors related to CKD.

Dietary interventions for mineral and bone disorder in people with chronic kidney disease

BACKGROUND

Chronic kidney disease-mineral and bone disorder (CKD-MBD) is a systemic dysfunction of mineral and bone metabolism in people with CKD. Recent research shows that phosphate retention plays a significant role in the development of CKD-MBD. Compared with drug therapies, dietary interventions may be simple, inexpensive and feasible for phosphate retention. However, there is little evidence to support these interventions.

OBJECTIVES

Our objective was to assess the benefits and harms of any dietary intervention for preventing and treating CKD-MBD.

SEARCH METHODS

We searched Cochrane Kidney and Transplant's Specialised Register to 27 August 2015 through contact with the Trials' Search Co-ordinator using search terms relevant to this review. We also searched the Chinese Biomedicine Database (CBM) (1976 to August 2015), China Knowledge Resource Integrated Database (CNKI) (1979 to August 2015), and VIP (1989 to August 2015).

SELECTION CRITERIA

Randomised controlled trials (RCTs) and quasi-RCTs looking at dietary interventions for prevention or treatment of CKD-MBD were eligible for inclusion.

DATA COLLECTION AND ANALYSIS

Two authors independently assessed the eligibility, methodological quality, and extracted data. Continuous outcomes (serum calcium level, serum phosphorus level, calcium × phosphate product, parathyroid hormone (PTH), fibroblast growth factor 23 (FGF-23) and alkaline phosphatase) were expressed as mean difference (MD) with 95% confidence interval (CI). Dichotomous outcomes (mortality) were expressed as risk ratio (RR) with 95% CI. We used a random-effects model to meta-analyse studies.

MAIN RESULTS

Nine studies were included in this review which analysed 634 participants. Study duration ranged from 4 to 24 weeks. The interventions included calcium-enriched bread, low phosphorus intake, low protein intake, very low protein intake, post haemodialysis supplements and hypolipaemic diet. Only one study reported death; none of the included studies reported cardiovascular events or fractures. There was insufficient reporting of design and methodological aspects among the included studies to enable robust assessment of risk of bias.There was limited and low-quality evidence to indicate that calcium-enriched bread increased serum calcium (1 study, 53 participants: MD -0.16 mmol/L, 95% CI -0.51 to -0.31), decreased serum phosphorus (53 participants: MD -0.41 mmol/L, 95% CI -0.51 to -0.31) and decreased the calcium × phosphate product (53 participants: MD -0.62 mmol²/L², 95% CI -0.77 to -0.47).Very low protein intake was not superior to conventional low protein intake in terms of effect on serum phosphorus (2 studies, 41 participants: MD -0.12 mmol/L, 95% CI -0.50 to 0.25), serum calcium (MD 0.00 mmol/L, 95% CI -0.17 to 0.17), or alkaline phosphatase (MD -22.00 U/L, 95% CI -78.25 to 34.25). PTH was significantly lower in the very low protein intake group (2 studies, 41 participants: MD -69.64 pmol/L, 95% CI -139.83 to 0.54).One study reported no significant difference in the number of deaths between low phosphorus intake and normal diet (279 participants: RR 0.18, 95% CI 0.01 to 3.82). Low phosphorus intake decreased serum phosphorus (2 studies, 359 participants: MD -0.18 mmol/L, 95% CI -0.29 to -0.07; I(2) = 0%).One study reported post-haemodialysis supplements did not increase serum phosphorus compared to normal diet (40 participants: MD 0.12 mmol/L, 95% CI -0.24 to 0.49).One study reported low phosphorus intake plus lanthanum carbonate significantly decreased FGF-23 (19 participants: MD -333.80 RU/mL, 95% CI -526.60 to -141.00), but did not decrease serum phosphorus (19 participants: MD -0.10 mg/dL, 95% CI -0.38 to 0.58) or PTH (19 participants: MD 31.60 pg/mL, 95% CI -29.82 to 93.02).

AUTHORS' CONCLUSIONS

There was limited low quality evidence to indicate that dietary interventions (calcium-enriched bread or low phosphorus/protein intake) may positively affect CKD-MBD by increasing serum calcium, decreasing serum phosphorus, the calcium × phosphate product and FGF-23. Large and well-designed RCTs are needed to evaluate the effects of various interventions for people with CKD-MBD.

Cardio-renal syndrome type 4: epidemiology, pathophysiology and treatment

Cardiovascular diseases such as coronary artery disease, congestive heart failure, arrhythmia, and sudden cardiac death represent the leading causes of morbidity and mortality in patients with CKD, increasing sharply as patients approach end-stage renal disease. The pathogenesis includes a complex, bidirectional interaction between the heart and kidneys that encompasses traditional and nontraditional risk factors, and has been termed cardio-renal syndrome type 4. In this review, an overview of the epidemiology and scope of this problem is provided, some suggested mechanisms for the pathophysiology of this disorder are discussed, and some of the key treatment strategies are described, with particular focus on recent clinical trials, both negative and positive.