The relationship between histopathological features, immunosuppression and outcome in patients undergoing native kidney biopsies.

AIMS: To assess retrospectively the association between histopathological lesions on renal biopsy and subsequent impairment of renal function across the spectrum of kidney diseases and to explore the influence of immunosuppressive therapy within the first 6 months after biopsy on this association. METHODS AND RESULTS: Clinical data from 488 adult patients having a renal biopsy reported at a single centre from 2017 to 2019 were obtained during a median follow-up period of 786 days. Seventeen semi-quantitative histology parameters were recorded at the time of biopsy, 14 of which were suitable for assessment of association with loss of eGFR by multivariable Cox regression analysis, measurement of eGFR slope and measurement of eGFR 12 months after biopsy. A widely used histopathological chronicity score was also assessed. Clinical baseline variables including prescription of immunosuppression were recorded. Seven of 14 histology parameters: mesangial matrix expansion, global glomerulosclerosis, tubular atrophy, interstitial fibrosis, arteriolosclerosis, mesangial hypercellularity and acute tubular injury; and the chronicity score, predicted loss of kidney function by all three measures. Prescription of immunosuppression was more likely in patients with active inflammatory pathology and less likely in patients with chronic fibrotic pathology, and was associated with reduced risk of loss of eGFR. CONCLUSIONS: This retrospective study demonstrates the prognostic significance and complex relationship with immunosuppression of routinely reported histopathological variables in patients having native kidney biopsies, across the spectrum of kidney diseases. It provides useful information for renal biopsy prognostication and design of retrospective studies, including machine learning models.

Outcomes in ANCA-Associated Vasculitis in Scotland: Validation of the Renal Risk Score in a Complete National Cohort.

Introduction: Antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) causes autoimmune-mediated inflammation of small blood vessels in multiple organs, including the kidneys. The ability to accurately predict kidney outcomes would enable a more personalized therapeutic approach. Methods: We used our national renal biopsy registry to validate the ability of ANCA Renal Risk Score (ARRS) to predict end-stage kidney disease (ESKD) for individual patients. This score uses histopathological and biochemical data to stratify patients as high, medium, or low risk for developing ESKD. Results: A total of 288 patients were eligible for inclusion in the study (low risk n = 144, medium risk n = 122, high risk n = 12). Using adjusted Cox proportional hazard models with the low-risk group as reference, we show that outcome differs between the categories: high-risk hazard ratio (HR) 16.69 (2.91-95.81, P = 0.002); medium risk HR 4.14 (1.07-16.01, P = 0.039). Incremental multivariable-adjusted Cox proportional hazards models demonstrated that adding ARRS to a model adjusted for multiple clinical parameters enhanced predictive discrimination (basic model C-statistic 0.864 [95% CI 0.813-0.914], basic model plus ARRS C-statistic 0.877 [95% CI 0.823-0.931]; P <0.01). Conclusion: The ARRS better discriminates risk of ESKD in AAV and offers clinicians more prognostic information than the use of standard biochemical and clinical measures alone. This is the first time the ARRS has been validated in a national cohort. The proportion of patients with high-risk scores is lower in our cohort compared to others and should be noted as a limitation of this study.

Increasing Collaborative Discussion in Case-Based Learning Improves Student Engagement and Knowledge Acquisition.

Background: In the transition from academic to clinical learning, the development of clinical reasoning skills and teamwork is essential, but not easily achieved by didactic teaching only. Case-based learning (CBL) was designed to stimulate discussions of genuine clinical cases and diagnoses but in our initial format (CBL'10) remained predominantly tutor-driven rather than student-directed. However, interactive teaching methods stimulate deep learning and consolidate taught material, and we therefore introduced a more collaborative CBL (cCBL), featuring a structured format with discussions in small breakout groups. This aimed to increase student participation and improve learning outcomes. Method: A survey with open and closed questions was distributed among 149 students and 36 tutors that had participated in sessions of both CBL formats. A statistical analysis compared exam scores of topics taught via CBL'10 and cCBL. Results: Students and tutors both evaluated the switch to cCBL positively, reporting that it increased student participation and enhanced consolidation and integration of the wider subject area. They also reported that the cCBL sessions increased constructive discussion and stimulated deep learning. Moreover, tutors found the more structured cCBL sessions easier to facilitate. Analysis of exam results showed that summative assessment scores of subjects switched to cCBL significantly increased compared to previous years, whereas scores of subjects that remained taught as CBL'10 did not change. Conclusions: Compared to our initial, tutor-led CBL format, cCBL resulted in improved educational outcomes, leading to increased participation, confidence, discussion and higher exam scores.

Seven suggestions for successful SGLT2i use in glomerular disease - a standalone CKD therapy?

PURPOSE OF REVIEW: Recent advances in the world of glomerular diseases have largely focussed on remission induction with immune modulating therapy. It is well recognised that even with the best available treatments, patients with glomerular diseases may have an increased risk of progressive renal and cardiovascular disease. RECENT FINDINGS: The arrival of large trials looking at the benefits of sodium-glucose cotransporter 2 inhibitors (SGLT2i) in patients with chronic kidney disease (CKD) and diabetes or not has shifted the entire focus of current management and the shift needs to go further. This review summarises the background to these landmark trials and provides practical guidance for implementation of the results in a general nephrology clinic. In sub-group analyses of the Dapagliflozin and Prevention of Adverse Outcomes in Chronic Kidney Disease (DAPA-CKD) clinical trial, SGLT2i improved renal outcomes in patients with immunoglobulin A (IgA) nephropathy highlighting the potential for this drug class in glomerular disease. We also discuss where the gaps in evidence are and where future trials in glomerular diseases, be they primary or secondary, should be focussed. SUMMARY: The renal community has never before had evidence of this strength upon which to base recommendations for patients with CKD and we should be grasping it with both hands.

ANCA-associated renal vasculitis is associated with rurality but not seasonality or deprivation in a complete national cohort study.

BACKGROUND: Small studies suggest an association between ANCA-associated vasculitis (AAV) incidence and rurality, seasonality and socioeconomic deprivation. We examined the incidence of kidney biopsy-proven AAV and its relationship with these factors in the adult Scottish population. METHODS: Using the Scottish Renal Biopsy Registry, all adult native kidney biopsies performed between 2014 and 2018 with a diagnosis of granulomatosis with polyangiitis (GPA) or microscopic polyangiitis (MPA) were identified. The Scottish Government Urban Rural Classification was used for rurality analysis. Seasons were defined as autumn (September-November), winter (December-February), spring (March-May) and summer (June-August). Patients were separated into quintiles of socioeconomic deprivation using the validated Scottish Index of Multiple Deprivation and incidence standardised to age. Estimated glomerular filtration rate and urine protein:creatinine ratio at time of biopsy were used to assess disease severity. RESULTS: 339 cases of renal AAV were identified, of which 62% had MPA and 38% had GPA diagnosis. AAV incidence was 15.1 per million population per year (pmp/year). Mean age was 66 years and 54% were female. Incidence of GPA (but not MPA) was positively associated with rurality (5.2, 8.4 and 9.1 pmp/year in 'urban', 'accessible remote' and 'rural remote' areas, respectively; p=0.04). The age-standardised incidence ratio was similar across all quintiles of deprivation (p=ns). CONCLUSIONS: Seasonality and disease severity did not vary across AAV study groups. In this complete national cohort study, we observed a positive association between kidney biopsy-proven GPA and rurality.

A National Registry Study of Patient and Renal Survival in Adult Nephrotic Syndrome.

INTRODUCTION: We aimed to determine the mortality rate, cause of death, and rate of end-stage kidney disease (ESKD) in adults with nephrotic syndrome (NS). METHODS: We conducted a national registry-based study, including all 522 adults who had a kidney biopsy for NS in Scotland in 2014-2017. We linked the Scottish Renal Registry to death certificate data. We performed survival and Cox proportional hazards analyses, accounting for competing risks of death and ESKD. We compared mortality rates with those in the age- and sex-matched general population. RESULTS: A total of 372 patients had primary NS; 150 had secondary NS. Over a median follow-up of 866 days, 110 patients (21%) died. In patients with primary NS, observed versus population 3-year mortality was 2.1% (95% CI 0.0%-4.6%) versus 0.9% (0.8%-1.0%) in patients aged <60 years and 24.9% (18.4%-30.8%) versus 9.4% (8.3%-10.5%) in those aged ≥60 years. In secondary NS, this discrepancy was 17.1% (5.6%-27.2%) versus 1.1% (0.9%-1.2%) in <60-year-olds and 49.4% (36.6%-59.7%) versus 8.1% (6.6%-9.6%) in ≥60-year-olds. In primary NS, cardiovascular causes accounted for 28% of deaths, compared with 18% in the general population. Eighty patients (15%) progressed to ESKD. Incidence of ESKD by 3 years was 8.4% (95% CI 4.9%-11.7%) in primary and 35.1% (24.3%-44.5%) in secondary NS. Early remission of proteinuria and the absence of early acute kidney injury (AKI) were associated with lower rates of death and ESKD. CONCLUSIONS: Adults with NS have high rates of death and ESKD. Cardiovascular causes account for excess mortality in primary NS.

Predicting outcome in acute interstitial nephritis: a case-series examining the importance of histological parameters.

AIMS: The clinical significance of common histological parameters in acute interstitial nephritis (AIN) is uncertain. We aimed to evaluate the utility of histology in predicting clinical outcomes in patients with AIN. METHODS AND RESULTS: Adult renal biopsies yielding a diagnosis of AIN between 2000 and 2015 were re-examined. Patients were divided into groups based on: (i) the percentage of non-fibrotic cortex containing inflammation (NFI score) (NFI-1 = 0-24%; NFI-2 = 25-74%; NFI-3 = 75-100%) and (ii) the percentage of cortex containing tubular atrophy (TA score) (TA1 = 0-9%; TA2 = 10-24%; TA3 = 25-100%). The primary outcome was a composite of ≥50% reduction in serum creatinine (sCr) or an estimated glomerular filtration rate (eGFR) > 60 ml/min/1.73 m2 1 year post-biopsy. From a total of 2817 native renal biopsies, there were 120 patients with AIN and adequate data for analysis. Of these, 66 (56%) achieved the primary outcome. On univariable logistic regression, NFI-3 was associated with a 16 times increased likelihood of achieving the primary outcome compared to NFI-1 [odds ratio (OR) = 16, 95% confidence interval (CI) = 5.2-50)]. In contrast, TA3 was associated with a 90% reduced likelihood of achieving the primary outcome compared to TA1 (OR = 0.10, 95% CI = 0.0-0.3). Maximal clinical utility was achieved by combining TA and NFI into a single prognostic 'TANFI' score, which had an independent predictive effect on the primary outcome in a multivariable regression model consisting of age, sex, baseline sCr and identified drug cause. CONCLUSIONS: In patients with biopsy-proven AIN, a lower percentage of cortical tubular atrophy and, paradoxically, a higher percentage of inflammation in non-fibrosed cortex were associated with an increased likelihood of a positive clinical outcome.

Obesity is not associated with progression to end stage renal disease in patients with biopsy-proven glomerular diseases.

BACKGROUND: Body mass index (BMI) is associated with renal disease progression in unspecified CKD. The relationship between BMI and primary glomerular disease (GN) may be more complex. We aimed to evaluate the association between BMI and renal disease progression in patients with primary glomerular disease (GN). METHODS: This was a single-centre retrospective cohort study performed in adult patients with biopsy-proven primary GN (excluding minimal change disease) from January 2000 to December 2015, with follow-up data until June 2017. BMI at time of biopsy was categorised as ≤25 kg/m2, > 25 to ≤30 kg/m2 and > 30 kg/m2. We used univariate and multivariate survival analyses to evaluate factors associated with progression to a composite endpoint of stage 5 CKD or renal replacement therapy (Major Adverse Renal Event - MARE) censoring for competing risk of death using Fine and Gray subdistribution hazards model. RESULTS: We included 560 patients with biopsy-proven primary GN and available BMI data: 66.1% were male with median age 54.8 (IQR 41.1-66.2) years and BMI 28.2 (IQR 24.9-32.1) kg/m2. Those with BMI 25-30 kg/m2 (n = 210) and with BMI > 30 kg/m2 (n = 207) were older (p = 0.007) with higher systolic and diastolic blood pressures (p = 0.02 and 0.004 respectively) than those with BMI < 25 kg/m2 (n = 132). There was a greater proportion of focal segmental glomerulosclerosis in those with higher BMI (3.9% in BMI < 25 kg/m2, 7.9% in BMI 25-30 kg/m2 and 10.7% in BMI > 30 kg/m2 of biopsies (p = 0.01)), but similar proportions of other GN diagnoses across BMI groups. Baseline eGFR (p = 0.40) and uPCR (p = 0.17) were similar across BMI groups. There was no interaction between BMI and time to MARE (log-rank p = 0.98) or death (log-rank p = 0.42). Censoring for competing risk of death, factors associated with progression to MARE were: younger age, lower baseline eGFR and higher uPCR, but not BMI (SHR 0.99, 95%CI 0.97-1.01, p = 0.31) nor blood pressure or GN diagnosis. CONCLUSION: BMI was not associated with progression to MARE in this patient cohort with primary GN. Efforts should be directed to managing other known risk factors for CKD progression.

Assessment of active tubulointerstitial nephritis in non-scarred renal cortex improves prediction of renal outcomes in patients with IgA nephropathy.

BACKGROUND: The addition of tubulointerstitial inflammation to the existing pathological classification of IgA nephropathy (IgAN) is appealing but was previously precluded due to reportedly wide inter-observer variability. We report a novel method to score percentage of non-atrophic renal cortex containing active tubulointerstitial inflammation (ATIN) in patients with IgAN and assess its utility to predict clinical outcomes. METHODS: All adult patients with a native renal biopsy diagnosis of IgAN between 2010 and 2015 in a unit serving 1.5 million people were identified. Baseline characteristics, biopsy reports and outcome data were collected. ATIN was calculated by subtracting the percentage of atrophic cortex from the percentage of total cortex with tubulointerstitial inflammation, with ≥10% representing significant ATIN. The primary outcome was a composite of requiring renal replacement therapy or doubling of serum creatinine. RESULTS: In total 153 new cases of IgAN were identified, of which 111 were eligible for inclusion. Of these, 76 (68%) were male and 54 (49%) had ATIN on biopsy. During a median follow-up of 2.3 years, 34 (31%) reached the primary outcome. On univariable Cox regression analysis, ATIN was associated with a five-fold increase in the primary outcome [hazard ratio (HR) (95% confidence interval) 4.9 (95% confidence interval (CI) 2.1-11.3)]. On multivariable analysis, mesangial hypercellularity, tubular atrophy and interstitial fibrosis and ATIN independently associated with renal outcome (P = 0.02 for ATIN). Inter-observer reproducibility revealed fair agreement in the diagnosis of ATIN (κ=0.43, P = 0.05). CONCLUSIONS: Within our centre, ATIN was significantly associated with renal outcome in patients with IgAN, independently of established histological features and baseline clinical characteristics.

Renal biopsy: it is time for pragmatism and consensus.

To obtain truly informed consent, we must be able to advise our patients accurately about the relative risk and benefit of any treatment plan. Percutaneous renal biopsy remains the gold standard investigation in the evaluation of intrinsic renal disease. There have been significant improvements in practice over the past decades with regards to percutaneous renal biopsy. Across centres, we appear now to have reached agreement on many aspects of this procedure, such as the need for blood pressure control, avoidance of coagulopathy, use of spring-loaded needles under direct imaging guidance and a need to monitor for complications. The authors from Rush University Medical Centre provide reassurance that renal biopsy in the modern era remains a safe procedure with a low rate of significant bleeding. There remain areas of divergence in practice that may have unintended and deleterious consequences: administration of desmopressin and discontinuation of aspirin, for example, both carry a risk of thrombosis. It is our opinion that it is time to reach consensus on our interpretation of the available data and to draw up guidelines to standardize our biopsy practice internationally.

Non-uniform relationship between salt status and aldosterone activity in patients with chronic kidney disease.

BACKGROUND: Hypertension is prevalent in chronic kidney disease (CKD). Studies suggest that reduction in dietary salt intake reduces blood pressure (BP). We studied relationships between salt intake, BP and renin-angiotensin system regulation in order to establish if it is disordered in CKD. METHODS: Mechanistic crossover study of CKD patients versus non-CKD controls. Participants underwent modified saline suppression test prior to randomization to either low or high salt diet for 5 days and then crossed over to the alternate diet. Angiotensin-II stimulation testing was performed in both salt states. BP, urea and electrolytes, and plasma aldosterone concentration (PAC) were measured. RESULTS: Twenty-seven subjects were recruited (12 CKD, 15 control). There was no difference in age and baseline BP between the groups. Following administration of intravenous saline, systolic BP increased in CKD but not controls (131 ± 16 to 139 ± 14 mmHg, P=0.016 vs 125 ± 20 to 128 ± 22 mmHg, P=0.38). Median PAC reduced from 184 (124,340) to 95 (80,167) pmol in controls (P=0.003), but failed to suppress in CKD (230 (137,334) to 222 (147,326) pmol (P=0.17)). Following dietary salt modification, there was no change in BP in either group. Median PAC was lower following high salt compared with low salt diet in CKD and controls. There was a comparable increase in systolic BP in response to angiotensin-II in both groups. DISCUSSION: We demonstrate dysregulation of aldosterone in CKD in response to salt loading with intravenous saline, but not to dietary salt modification.

Risk factors for bleeding complications after nephrologist-performed native renal biopsy.

BACKGROUND: Bleeding is a recognized complication of native percutaneous renal biopsy. This study aimed to describe the incidence of major bleeding after biopsy in a single centre over a 15-year period and examine factors associated with major bleeding. METHODS: We identified consecutive adult patients undergoing ultrasound-guided native renal biopsy in the Glasgow Renal and Transplant Unit from 2000 to 2014. From the electronic patient record, we collected data pertaining to biopsy indication, pre- and post-biopsy laboratory measurements, prescribed medication and diagnosis. Aspirin was routinely continued. We defined major bleeding post-biopsy as the need for blood transfusion, surgical or radiological intervention or death. Binary logistic regression analysis was used to assess factors associated with increased risk of major bleeding. RESULTS: There were 2563 patients who underwent native renal biopsy (1499 elective, 1064 emergency). The average age of patients was 57 (SD 17) years and 57.4% were male. Overall, the rate of major bleeding was 2.2%. In all, 46 patients required transfusion (1.8%), 9 patients underwent embolization (0.4%), no patient required nephrectomy and 1 patient died as a result of a significant late retroperitoneal bleed. Major bleeding was more common in those undergoing emergency compared with elective renal biopsy (3.4 versus 1.1%; P < 0.001). Aspirin was being taken at the time of biopsy in 327 of 1509 patients, with no significant increase in the risk of major bleeding (P = 0.93). Body mass index (BMI) data were available for 546 patients, with no increased risk of major bleeding in 207 patients classified as obese (BMI >30). CONCLUSIONS: The risk of major bleeding following native renal biopsy in the modern era is low. Complications are more common when biopsy is conducted as an emergency, which has implications for obtaining informed consent. Our data support the strategy of not stopping aspirin before renal biopsy.

Multiple socioeconomic deprivation and impact on survival in patients with primary glomerulonephritis.

Background: The impact of multiple socio-economic deprivation on patient outcomes in primary renal diseases is unknown. We aimed to assess whether risk of death or requiring renal replacement therapy (RRT) in patients with primary glomerulonephritis (GN) was higher in patients living in an area of multiple socio-economic deprivation. Methods: Patients undergoing native renal biopsy between 2000 and 2014 were identified. Baseline demographics, postcode at time of biopsy, follow-up blood pressure, proteinuria and time to death or RRT were recorded. The Scottish Index of Multiple Deprivation (SIMD) is a multidimensional model used to measure deprivation based on postcode. Using SIMD, patients were separated into tertiles of deprivation. Results: A total of 797 patients were included, 64.2% were male with mean age of 54.1 (standard deviation 17.0) years. Median follow-up was 6.3 (interquartile range 3.7-9.4) years during which 174 patients required RRT and 185 patients died. Patients in the most deprived tertile of deprivation were significantly more likely to die than those in the least deprived tertile [hazard ratio (HR) 2.2, P < 0.001], independent of age, baseline serum creatinine and blood pressure. They were not more likely to require RRT (P = 0.22). The increased mortality risk in the most deprived tertile was not uniform across primary renal diseases, with the association being most marked in focal segmental glomerulosclerosis (HR 7.4) and IgA nephropathy (HR 2.7) and absent in membranous nephropathy. Conclusion: We have demonstrated a significant independent 2-fold increased risk of death in patients with primary GN who live in an area of multiple socio-economic deprivation at the time of diagnosis as compared with those living in less deprived areas.

Continued monitoring of acute kidney injury survivors might not be necessary in those regaining an estimated glomerular filtration rate >60 mL/min at 1 year.

Background: Severe acute kidney injury (AKI) among hospitalized patients often necessitates initiation of short-term dialysis. Little is known about the long-term outcome of those who recover to normal renal function. The aim of this study was to determine the long-term renal outcome of patients experiencing AKI requiring dialysis secondary to hypoperfusion injury and/or sepsis who recovered to apparently normal renal function. Methods: All adult patients with AKI requiring dialysis in our centre between 1 January 1980 and 31 December 2010 were identified. We included patients who had estimated glomerular filtration rate (eGFR) >60 mL/min/1.73 m 2 12 months or later after the episode of AKI. Patients were followed up until 3 March 2015. The primary outcome was time to chronic kidney disease (CKD) (defined as eGFR persistently <60 mL/min/1.73 m 2 ) from first dialysis for AKI. Results: Among 2922 patients with a single episode of dialysis-requiring AKI, 396 patients met the study inclusion criteria. The mean age was 49.8 (standard deviation 16.5) years and median follow-up was 7.9 [interquartile range (IQR) 4.8-12.7] years. Thirty-five (8.8%) of the patients ultimately developed CKD after a median of 5.3 (IQR 2.8-8.0) years from first dialysis for AKI giving an incidence rate of 1 per 100 person-years. Increasing age, diabetes and vascular disease were associated with higher risk of progression to CKD [adjusted hazard ratios (95% confidence interval): 1.06 (1.03, 1.09), 3.05 (1.41, 6.57) and 3.56 (1.80, 7.03), respectively]. Conclusions: Recovery from AKI necessitating in-hospital dialysis was associated with a very low risk of progression to CKD. Most of the patients who progressed to CKD had concurrent medical conditions meriting monitoring of renal function. Therefore, it seems unlikely that regular follow-up of renal function is beneficial in patients who recover to eGFR >60 mL/min/1.73 m 2 by 12 months after an episode of AKI.

Venous Thromboembolism in Primary Nephrotic Syndrome - Is the Risk High Enough to Justify Prophylactic Anticoagulation?

BACKGROUND: The reported incidence of venous thromboembolism (VTE) in patients with nephrotic syndrome (NS) varies widely, as does the approach to prophylactic anticoagulation. We aimed to assess the incidence of VTE in patients with primary NS in order to inform a sample size calculation to determine if a future clinical trial will ever be feasible. METHODS: All adults undergoing native renal biopsy for NS between 2008 and 2013 yielding a diagnosis of primary glomerulonephritis were identified. Baseline serum albumin, urine protein:creatinine ratio, estimated glomerular filtration rate, date of biopsy and histological diagnosis were recorded. Episodes of objectively verified VTE were identified using the electronic patient record. Sample size calculations were performed based on 2 independent samples with a dichotomous outcome and to achieve a power of 80% and p < 0.05. RESULTS: Two hundred six patients were included of which 60% were male and mean age at biopsy was 55 years (SD 19). Median follow-up was 2.9 years (interquartile range (IQR) 1.6-4.7). Fourteen (6.8%) patients suffered VTE. Median time to diagnosis of VTE from renal biopsy was 36 days (IQR -22 to 178), with 6 VTEs occurring prior to biopsy and 1 during remission. In a total of 270 patient years of NS, there were 7 VTE that could potentially have been avoided if anticoagulation was given for the duration of NS, that is, 2.6% risk per year of NS; this risk was highest for patients with minimal change nephropathy at 13.3% per year of NS, compared to 0.65% per year of NS for those with idiopathic membranous nephropathy. Assuming a 75% reduction in the incidence of VTE with prophylactic anticoagulation, 972 participants would be required for a future clinical trial to have 80% power. CONCLUSIONS: Patients with primary NS are at an increased risk of VTE. The timing of VTE means that only half of episodes would be targeted by prophylactic anticoagulation. Given the low frequency of events, a well-powered clinical trial would be challenging to achieve.

Association between urinary sodium, creatinine, albumin, and long-term survival in chronic kidney disease.

Dietary sodium intake is associated with hypertension and cardiovascular risk in the general population. In patients with chronic kidney disease, sodium intake has been associated with progressive renal disease, but not independently of proteinuria. We studied the relationship between urinary sodium (UNa) excretion and UNa to creatinine ratio and mortality or requirement for renal replacement therapy in chronic kidney disease. Adult patients attending a renal clinic who had ≥1 24-hour UNa measurement were identified. Twenty-four-hour UNa measures were collected and UNa to creatinine ratio calculated. Time to renal replacement therapy or death was recorded. Four hundred twenty-three patients were identified with mean estimated glomerular filtration rate of 48 mL/min per 1.73 m(2). Ninety patients required renal replacement therapy and 102 patients died. Mean slope decline in estimated glomerular filtration rate was -2.8 mL/min per 1.73 m(2) per year. Median follow-up was 8.5 years. Patients who died or required renal replacement therapy had significantly higher UNa excretion and UNa to creatinine ratio, but the association with these parameters and poor outcome was not independent of renal function, age, and albuminuria. When stratified by albuminuria, UNa to creatinine ratio was a significant cumulative additional risk for mortality, even in patients with low-level albuminuria. There was no association between low UNa and risk, as observed in some studies. This study demonstrates an association between UNa excretion and mortality in chronic kidney disease, with a cumulative relationship between sodium excretion, albuminuria, and reduced survival. These data support reducing dietary sodium intake in chronic kidney disease, but additional study is required to determine the target sodium intake.

The incidence of biopsy-proven IgA nephropathy is associated with multiple socioeconomic deprivation.

Chronic kidney disease is more common in areas of socioeconomic deprivation, but the relationship with the incidence and diagnosis of biopsy-proven renal disease is unknown. In order to study this, all consecutive adult patients undergoing renal biopsy in West and Central Scotland over an 11-year period were prospectively analyzed for demographics, indication, and histologic diagnosis. Using the Scottish Index of Multiple Deprivation, 1555 eligible patients were separated into quintiles of socioeconomic deprivation according to postcode. Patients in the most deprived quintile were significantly more likely to undergo biopsy compared with patients from less deprived areas (109.5 compared to 95.9 per million population/year). Biopsy indications were significantly more likely to be nephrotic syndrome, or significant proteinuria without renal impairment. Patients in the most deprived quintile were significantly more likely to have glomerulonephritis. There was a significant twofold increase in the diagnosis of IgA nephropathy in the patients residing in the most compared with the least deprived postcodes not explained by the demographics of the underlying population. Thus, patients from areas of socioeconomic deprivation in West and Central Scotland are significantly more likely to undergo native renal biopsy and have a higher prevalence of IgA nephropathy.