Design and methods of the REMOVAL-HD study: a tRial Evaluating Mid cut-Off Value membrane clearance of Albumin and Light chains in HaemoDialysis patients

Light Chain Cast Nephropathy in Multiple Myeloma: Prevalence, Impact and Management Challenges

“Cast nephropathy” (CN) is a pathological feature of myeloma kidney, also seen to a lesser extent in the context of severe nephrotic syndrome from non-haematological diseases. The name relates to obstruction of distal tubules by “casts” of luminal proteins concentrated by intensive water reabsorption resulting from dehydration or high-dose diuretics. Filtered proteins form complexes with endogenous tubular Tamm-Horsfall glycoprotein. The resulting gel further slows or stops luminal flow upon complete obstruction of distal convoluted tubules and collecting ducts. Thus, a tubular obstructive form of acute kidney injury (AKI) is a common consequence of CN. The pathogenesis of CN will be reviewed in light of recent advances in the understanding of monoclonal disorders of B lymphocytes, leading to the release of immunoglobulin components (free light chains, FLC) into the bloodstream and their filtration across the glomerular basement membrane. Treatment aiming at reduction of the circulating burden of FLC may help recovery of renal function in a fraction of these patients, besides filling the void between the onset of AKI, histopathological diagnosis, and full response to pharmacologic treatment.

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Acute Kidney Injury in Monoclonal Gammopathies

Monoclonal gammopathies (MG) encompass a variety of disorders related to clonal expansion and/or malignant transformation of B lymphocytes. Deposition of free immunoglobulin (Ig) components (light or heavy chains, LC/HC) within the kidney during MG may result over time in multiple types and degrees of injury, including acute kidney injury (AKI). AKI is generally a consequence of tubular obstruction by luminal aggregates of LC, a pattern known as “cast nephropathy”. Monoclonal Ig LC can also be found as intracellular crystals in glomerular podocytes or proximal tubular cells. Proliferative glomerulonephritis with monoclonal Ig deposits is another, less frequent form of kidney injury with a sizable impact on renal function. Hypercalcemia (in turn related to bone reabsorption triggered by proliferating plasmacytoid B cells) may lead to AKI via functional mechanisms. Pharmacologic treatment of MG may also result in additional renal injury due to local toxicity or the tumor lysis syndrome. The present review focuses on AKI complicating MG, evaluating predictors, risk factors, mechanisms of damage, prognosis, and options for treatment.

Renal replacement therapy in cancer patients with acute kidney injury (Review)

Cancer patients are at high risk for developing acute kidney injury (AKI), which is associated with increased morbidity and mortality in these patients. Despite the progress made in understanding the pathogenic mechanisms and etiology of AKI in these patients, the main prevention consists of avoiding medication and nephrotoxic agents such as non-steroidal anti-inflammatory drugs, contrast agents used in medical imaging and modulation of chemotherapy regimens; when prophylactic measures are overcome and renal impairment becomes unresponsive to treatment, renal replacement therapy (RRT) is required. There are several methods of RRT that can be utilized for patients with malignancies and acute renal impairment; the choice of treatment being based on the patient characteristics. The aim of this article is to review the literature data regarding the epidemiology and management of AKI in cancer patients, the extracorporeal techniques used, choice of the appropriate therapy and the optimal time of initiation, and also the dose-prognosis relationship.

Effect of a medium cut-off dialyzer on protein-bound uremic toxins and mineral metabolism markers in patients on hemodialysis

INTRODUCTION

Hemodialysis (HD) with medium cut-off (MCO) dialyzers may expand molecular clearance, predominantly larger middle molecules (molecular weight 25-60 kDa). However, the impact of MCO dialyzers on long-term clearance of various other components of the uremic milieu is unknown. The tRial Evaluating Mid cut-Off Value membrane clearance of Albumin and Light chains in HemoDialysis patients (REMOVAL-HD) provided an opportunity to assess the effect of MCO dialyzers on protein-bound uremic toxins and novel markers of mineral metabolism.

METHODS

This exploratory sub-study of REMOVAL-HD evaluated changes in protein-bound solutes (total and free indoxyl sulfate [IS] and p-cresyl sulfate [PCS]) and mineral metabolism markers (intact fibroblast growth factor-23 [iFGF23], fetuin-A and endogenous calciprotein particles [CPP-1 and CPP-2]). Mid-week, pre-HD serum samples were collected at baseline and after 12 and 24 weeks of MCO use in stable adult patients. Change from baseline to Week 12 and 24 was estimated using linear mixed effects models.

FINDINGS

Eighty-nine participants were studied (mean age 67 ± 15 years, 38% female, 51% diabetic, median urine output 200 ml/24 h). Serum iFGF23 was reduced at Week 12 compared to baseline (-26.8% [95%CI -39.7, -11.1], p = 0.001), which was sustained at Week 24 (-21.7% [95%CI -35.7, -4.5], p = 0.012). There was no significant change in serum IS, PCS, fetuin-A, CPP-1, or CPP-2.

DISCUSSION

The use of a MCO dialyzer over 24 weeks was associated with a sustained reduction in FGF23, while other measured components of the uremic milieu were not significantly altered. Further studies are required to determine whether FGF23 reduction is associated with improved patient outcomes.

Slipping Through the Pores: Hypoalbuminemia and Albumin Loss During Hemodialysis

Hypoalbuminemia results when compensatory mechanisms are unable to keep pace with derangements in catabolism/loss and/or decreased synthesis of albumin. Across many disease states, including chronic kidney disease (CKD), hypoalbuminemia is a well-established, independent risk factor for adverse outcomes, including mortality. In the setting of CKD, reduced serum albumin concentrations are often a manifestation of protein-energy wasting, a state of metabolic and nutritional alterations resulting in reduced protein and energy stores. The progression of CKD to kidney failure and the initiation of maintenance hemodialysis (HD) further predisposes an already at-risk population toward hypoalbuminemia such that approximately 60% of HD patients have albumin concentrations <4.0 g/dl. Albumin loss into the dialysate through the dialyzer appears to be a potentially modifiable cause of hypoalbuminemia in some patients. A group of newer dialyzers for maintenance HD-sometimes termed protein-leaking or medium cut-off membranes-aim to improve clearance of middle molecules (vs high flux dialyzers) but are associated with increased albumin losses. In this article, we will examine the impact of dialyzer selection on albumin losses during conventional HD, including the clinical relevance of such losses on serum albumin levels. Data on the clinical relevance of albumin losses during dialysis and current gaps in the evidence base are also discussed.

Effects of medium cut-off dialysis membranes on inflammation and oxidative stress in patients on maintenance hemodialysis

PURPOSE

Medium cut-off membranes were developed for providing increased clearance of larger middle-molecule uremic toxins. We compared the effect of low-flux, medium cut-off, and high-flux membranes on chronic inflammation and oxidative stress in patients with maintenance hemodialysis.

METHODS

A total of 42 patients were enrolled in this study. Total antioxidant status, total oxidant status, paraoxonase-1, ischemia-modified albumin, total Thiol, disulfide bond, and native Thiol were measured to determine oxidative stress. C-reactive protein was measured to define inflammation.

RESULTS

37% of the total patients were females, and the mean age was 52.9 ± 16 years. Serum albumin and Kt/V were similar between groups during the study period. We did not find any significant difference at baseline in the 3rd and 6th months of the study when we compared the inflammatory marker and oxidative indicator levels between three hemodialysis membranes in the whole study group. In the subgroup analysis of 19 patients with a high C-reactive protein level, we found that the medium cut-off membrane significantly reduced serum C-reactive protein level, when compared to low-flux and high-flux membrane [2.8 mg/L vs. 13.7 mg/L and 6.1 mg/L, respectively, p = 0.05]. However, we did not find a significant change in oxidative stress indicators in patients with high C-reactive protein levels between the three dialysers.

CONCLUSION

The medium cut-off membrane has favorable effects on inflammation in patients with maintenance hemodialysis. However, this positive effect could not be demonstrated in oxidative stress.