Chronic renal confusion: insufficiency, failure, dysfunction, or disease

Unbiased kidney-centric molecular categorization of chronic kidney disease as a step towards precision medicine

Current classification of chronic kidney disease (CKD) into stages using indirect systemic measures (estimated glomerular filtration rate (eGFR) and albuminuria) is agnostic to the heterogeneity of underlying molecular processes in the kidney thereby limiting precision medicine approaches. To generate a novel CKD categorization that directly reflects within kidney disease drivers we analyzed publicly available transcriptomic data from kidney biopsy tissue. A Self-Organizing Maps unsupervised artificial neural network machine-learning algorithm was used to stratify a total of 369 patients with CKD and 46 living kidney donors as healthy controls. Unbiased stratification of the discovery cohort resulted in identification of four novel molecular categories of disease termed CKD-Blue, CKD-Gold, CKD-Olive, CKD-Plum that were replicated in independent CKD and diabetic kidney disease datasets and can be further tested on any external data at kidneyclass.org. Each molecular category spanned across CKD stages and histopathological diagnoses and represented transcriptional activation of distinct biological pathways. Disease progression rates were highly significantly different between the molecular categories. CKD-Gold displayed rapid progression, with significant eGFR-adjusted Cox regression hazard ratio of 5.6 [1.01-31.3] for kidney failure and hazard ratio of 4.7 [1.3-16.5] for composite of kidney failure or a 40% or more eGFR decline. Urine proteomics revealed distinct patterns between the molecular categories, and a 25-protein signature was identified to distinguish CKD-Gold from other molecular categories. Thus, patient stratification based on kidney tissue omics offers a gateway to non-invasive biomarker-driven categorization and the potential for future clinical implementation, as a key step towards precision medicine in CKD.

Identification and outcomes of KDIGO-defined chronic kidney disease in 1.4 million U.S. Veterans with heart failure

AIMS

According to the Kidney Disease: Improving Global Outcomes (KDIGO) guideline, the definition of chronic kidney disease (CKD) requires the presence of abnormal kidney structure or function for >3 months with implications for health. CKD in patients with heart failure (HF) has not been defined using this definition, and less is known about the true health implications of CKD in these patients. The objective of the current study was to identify patients with HF who met KDIGO criteria for CKD and examine their outcomes.

METHODS AND RESULTS

Of the 1 419 729 Veterans with HF not receiving kidney replacement therapy, 828 744 had data on ≥2 ambulatory serum creatinine >90 days apart. CKD was defined as estimated glomerular filtration rate (eGFR) <60 ml/min/1.73 m2 (n = 185 821) or urinary albumin-to-creatinine ratio (uACR) >30 mg/g (n = 32 730) present twice >3 months apart. Normal kidney function (NKF) was defined as eGFR ≥60 ml/min/1.73 m2, present for >3 months, without any uACR >30 mg/g (n = 365 963). Patients with eGFR <60 ml/min/1.73 m2 were categorized into four stages: 45-59 (n = 72 606), 30-44 (n = 74 812), 15-29 (n = 32 077), and <15 (n = 6326) ml/min/1.73 m2. Five-year all-cause mortality occurred in 40.4%, 57.8%, 65.6%, 73.3%, 69.7%, and 47.5% of patients with NKF, four eGFR stages, and uACR >30mg/g (albuminuria), respectively. Compared with NKF, hazard ratios (HR) (95% confidence intervals [CI]) for all-cause mortality associated with the four eGFR stages and albuminuria were 1.63 (1.62-1.65), 2.00 (1.98-2.02), 2.49 (2.45-2.52), 2.28 (2.21-2.35), and 1.22 (1.20-1.24), respectively. Respective age-adjusted HRs (95% CIs) were 1.13 (1.12-1.14), 1.36 (1.34-1.37), 1.87 (1.84-1.89), 2.24 (2.18-2.31) and 1.19 (1.17-1.21), and multivariable-adjusted HRs (95% CIs) were 1.11 (1.10-1.12), 1.24 (1.22-1.25), 1.46 (1.43-1.48), 1.42 (1.38-1.47), and 1.13 (1.11-1.16). Similar patterns were observed for associations with hospitalizations.

CONCLUSION

Data needed to define CKD using KDIGO criteria were available in six out of ten patients, and CKD could be defined in seven out of ten patients with data. HF patients with KDIGO-defined CKD had higher risks for poor outcomes, most of which was not explained by abnormal kidney structure or function. Future studies need to examine whether CKD defined using a single eGFR is characteristically and prognostically different from CKD defined using KDIGO criteria.

Efficacy, tolerability, and safety of oral sulfate tablet versus 2 L-polyethylene glycol/ascorbate for bowel preparation in older patients: prospective, multicenter, investigator single-blinded, randomized study

BACKGROUND

We compared the efficacy, tolerability, and safety of oral sulfate tablets (OST, which contains simethicone) and 2 L-polyethylene glycol/ascorbate (2 L-PEG/Asc) with a split-dosing regimen in older individuals aged ≥ 70 years who underwent scheduled colonoscopy.

METHODS

This prospective, randomized, investigator-blinded, multicenter study was conducted between June 2022 and October 2023. Participants aged ≥ 70 years were randomized at a ratio of 1:1 to the OST or 2 L-PEG/Asc groups.

RESULTS

In total, 254 patients were evaluated using a modified full analysis set. Successful overall bowel preparation was excellent and similar between the OST and 2 L-PEG/Asc groups for the Boston Bowel Preparation Scale (BBPS) (96.5% vs. 96.6%) and Harefield Cleansing Scale (HCS) (96.5% vs. 97.4%). The overall high-quality preparation rate was higher in the OST group than in the 2 L-PEG/Asc group (BBPS: 55.7% vs. 28.4%, P < 0.001; HCS: 66.1% vs. 38.8%, P < 0.001). The overall adenoma detection rate (54.8% vs. 35.3, P = 0.003) was superior in the OST group compared to the 2 L-PEG/Asc group. Tolerability scores, including overall satisfaction, were generally higher in the OST group than in the 2 L-PEG/Asc group. The incidence of major solicited adverse events was comparable between the two groups (55.7% vs. 68.1, P = 0.051), and there were no clinically significant changes in the serum laboratory profiles on the day of or 7 days after colonoscopy.

CONCLUSIONS

OST is an effective and safe low-volume agent for colonoscopy, with better tolerance than 2 L-PEG/Asc, in older individuals aged ≥ 70 years.

Organic solvent exposure for the chronic kidney disease: updated systematic review with meta-analysis

Background

Studies on the relationship between organic solvent exposure and chronic kidney disease (CKD) have presented inconsistent results. Definition of CKD has changed in 2012, and other cohort studies have been newly published. Therefore, this study aimed to newly confirm the relationship between organic solvent exposure and CKD through an updated meta-analysis including additional studies.

Methods

This systematic review was conducted in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) guidelines. The search was conducted on January 2, 2023 using Embase and MEDLINE databases. Case-control and cohort studies on the relationship between organic solvent exposure and CKD were included. Two authors independently reviewed full-text.

Results

Of 5,109 studies identified, a total of 19 studies (control studies: 14 and cohort studies: 5) were finally included in our meta-analysis. The pooled risk of CKD in the organic solvent exposed group was 2.44 (1.72-3.47). The risk of a low-level exposure group was 1.07 (0.77-1.49). The total risk of a high-level exposure group was 2.44 (1.19-5.00). The risk of glomerulonephritis was 2.69 (1.18-6.11). The risk was 1.46 (1.29-1.64) for worsening of renal function. The pooled risk was 2.41 (1.57-3.70) in case-control studies and 2.51 (1.34-4.70) in cohort studies. The risk of subgroup classified as 'good' by the Newcastle Ottawa scale score was 1.93 (1.43-2.61).

Conclusions

This study confirmed that the risk of CKD was significantly increased in workers exposed to mixed organic solvents. Further research is needed to determine the exact mechanisms and thresholds. Surveillance for kidney damage in the group exposed to high levels of organic solvents should be conducted.

Trial Registration

PROSPERO Identifier: CRD42022306521.

Barriers to conservative care from patients' and nephrologists' perspectives: the CKD-REIN study

BACKGROUND

Conservative care is increasingly considered an alternative to kidney replacement therapy for kidney failure management, mostly among the elderly. We investigated its status and the barriers to its implementation from patients' and providers' perspectives.

METHODS

We analysed data from 1204 patients with advanced chronic kidney disease (CKD) [estimated glomerular filtration rate (eGFR) <30 mL/min/1.73 m2] enrolled at 40 nationally representative nephrology clinics (2013-16) who completed a self-administered questionnaire about the information they received and their preferred treatment option, including conservative care, if their kidneys failed. Nephrologists (n = 137) also reported data about their clinics' resources and practices regarding conservative care.

RESULTS

All participating facilities reported they were routinely able to offer conservative care, but only 37% had written protocols and only 5% had a person or team primarily responsible for it. Overall, 6% of patients were estimated to use conservative care. Among nephrologists, 82% reported they were fairly or extremely comfortable discussing conservative care, but only 28% usually or always offered this option for older (>75 years) patients approaching kidney failure. They used various terminology for this care, with conservative management and non-dialysis care mentioned most often. Among patients, 5% of those >75 years reported receiving information about this option and 2% preferring it.

CONCLUSIONS

Although reported by nephrologists to be widely available and easily discussed, conservative care is only occasionally offered to older patients, most of whom report they were not informed of this option. The lack of a person or team responsible for conservative care and unclear information appear to be key barriers to its implementation.

[Nomenclature for kidney function and kidney diseases - Improving assessment and prognosis through precision and comprehensibility]

Nierenkrankheiten stellen ein zunehmendes Gesundheitsproblem dar, dessen Eindämmung eine effektive Kommunikation zwischen den an Erfassung, Diagnostik und Therapie Beteiligten sowie den betroffenen Patientinnen und Patienten erfordert. Die Nomenklatur für Nierenfunktion und Nierenkrankheiten ist jedoch bislang nicht einheitlich. Die internationale, gemeinnützige Organisation Kidney Disease: Improving Global Outcomes (KDIGO) hat deshalb 2019 in einem Konsensus-Prozess ein englischsprachiges Glossar entwickelt, um die Begriffe zur Beschreibung von Nierenfunktion, Nierenstruktur und Nierenkrankheiten zu vereinheitlichen. Leitprinzipien bei der Entwicklung dieser Nomenklatur waren (1) Präzision, (2) Patientenzentrierung und (3) Konsistenz mit bisherigen KDIGO-Leitlinien. Das vorliegende Positionspapier beinhaltet eine deutsche Übersetzung dieses Glossars, die im Auftrag der nephrologischen Fachgesellschaften in Deutschland, Österreich und der Schweiz entwickelt wurde.

Nomenclature for kidney function and disease-executive summary and glossary from a Kidney Disease: Improving Global Outcomes (KDIGO) consensus conference

The worldwide burden of kidney disease is rising, but public awareness remains limited, underscoring the need for more effective communication by stakeholders in the kidney health community. Despite this need for clarity, the nomenclature for describing kidney function and disease lacks uniformity. In June 2019, Kidney Disease: Improving Global Outcomes (KDIGO) convened a consensus conference with the goal of standardizing and refining the nomenclature used in the English language to describe kidney function and disease, and of developing a glossary that could be used by journals in scientific publications. Guiding principles of the conference were that the revised nomenclature should be patient-centred, precise, and consistent with nomenclature used in the KDIGO guidelines. Conference attendees reached general consensus on the following recommendations: (i) to use 'kidney' rather than 'renal' or 'nephro' when referring to kidney disease and kidney function; (ii) to use 'kidney failure' with appropriate descriptions of the presence or absence of symptoms, signs, and treatment rather than 'end-stage' kidney disease; (iii) to use the KDIGO definition and classification of acute kidney diseases and disorders (AKD) and acute kidney injury (AKI) rather than alternative descriptions to define and classify the severity of AKD and AKI; (iv) to use the KDIGO definition and classification of chronic kidney disease (CKD) rather than alternative descriptions to define and classify the severity of CKD; and (v) to use specific kidney measures, such as albuminuria or decreased glomerular filtration rate, rather than 'abnormal or reduced kidney function' to describe alterations in kidney structure and function. A proposed five-part glossary contains specific items for which there was general agreement. Conference attendees acknowledged limitations of the recommendations and glossary but considered that standardizing scientific nomenclature is essential for improving communication.

Prevalence of Vas Deferens Calcifications on Abdominal CT Examinations and Association With Systemic Conditions

OBJECTIVE. The purpose of this study was to describe the prevalence of vas deferens (VD) calcifications on abdominal CT examinations and the associations between VD calcifications and several systemic conditions. MATERIALS AND METHODS. The CT examinations of male patients from January 2010 to December 2011 were retrospectively reviewed. After exclusions, the records of 1915 consecutively identified patients were analyzed. Five readers, 3rd- and 4th-year radiology residents, recorded the presence and laterality of VD calcifications and of vascular calcifications presumed due to atherosclerosis. A sixth reader parsed the patient records for diagnoses of type 2 diabetes mellitus (DM) and chronic kidney disease (CKD). RESULTS. The mean age of the entire sample population was 52.9 ± 18.9 years (range, 1-93 years). The mean age of patients with VD calcifications was 59.3 ± 12.0 (SD) years and of the group without VD calcifications was 52.9 ± 19.1 years (p = 0.17). The prevalence of VD calcification was 1.61% (31 patients): 21 (67.7%) of the patients had bilateral calcification; seven (22.6%), right-sided only; and three, (9.7%) left-sided. The frequency of DM was 28.8% (551/1915), of CKD was 7.58% (150/1915), and of atherosclerosis, 60.4% (1156/1915). The mean caliber of calcified VDs was 5.31 ± 1.29 mm versus 3.63 ± 0.63 mm for patients without calcification or any chronic condition (p < 0.0001). Among age, atherosclerosis, DM, and CKD in univariate regression analysis, only DM was associated with VD calcification (p = 0.006). However, because age (p = 0.063) and atherosclerosis (p = 0.057) were close to significant, they were included in the multivariate analysis, which also showed only DM associated with VD calcification (odds ratio, 2.14 ± 0.85). CONCLUSION. In the large cohort in this study, the prevalence of VD calcification was 1.61%. VD calcification was strongly associated with DM. The pathologic implications of VD calcification remain unclear and warrant further investigation in prospective longitudinal studies.

Nomenclature for Kidney Function and Disease: Executive Summary and Glossary From a Kidney Disease: Improving Global Outcomes (KDIGO) Consensus Conference

This article is being published in Kidney International Reports and reprinted concurrently in several journals. The articles cover identical concepts and wording but vary in minor stylistic and spelling changes, detail, and length of manuscript, in keeping with each journal's style. Any of these versions may be used in citing this article. Excerpts are adapted with permission of KDIGO and the International Society of Nephrology.

Patient and Caregiver Perspectives on Terms Used to Describe Kidney Health

BACKGROUND AND OBJECTIVES

The language used to communicate important aspects of kidney health is inconsistent and may be conceptualized differently by patients and health professionals. These problems may impair the quality of communication, care, and patient outcomes. We aimed to describe the perspectives of patients on terms used to describe kidney health.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Patients with CKD (n=54) and caregivers (n=13) from the United States, United Kingdom, and Australia participated in ten focus groups to discuss terms for kidney health (including kidney, renal, CKD, ESKD, kidney failure, and descriptors for kidney function). We analyzed the data using thematic analysis.

RESULTS

We identified four themes: provoking and exacerbating undue trauma (fear of the unknown, denoting impending death, despair in having incurable or untreatable disease, premature labeling and assumptions, judgment, stigma, and failure of self); frustrated by ambiguity (confused by medicalized language, lacking personal relevance, baffled by imprecision in meaning, and/or opposed to obsolete terms); making sense of the prognostic enigma (conceptualizing level of kidney function, correlating with symptoms and effect on life, predicting progression, and need for intervention); and mobilizing self-management (confronting reality, enabling planning and preparation, taking ownership for change, learning medical terms for self-advocacy, and educating others).

CONCLUSIONS

The obscurity and imprecision of terms in CKD can be unduly distressing and traumatizing for patients, which can impair decision making and self-management. Consistent and meaningful patient-centered terminology may improve patient autonomy, satisfaction, and outcomes.

Nomenclature for kidney function and disease: report of a Kidney Disease: Improving Global Outcomes (KDIGO) Consensus Conference

The worldwide burden of kidney disease is rising, but public awareness remains limited, underscoring the need for more effective communication by stakeholders in the kidney health community. Despite this need for clarity, the nomenclature for describing kidney function and disease lacks uniformity. In June 2019, Kidney Disease: Improving Global Outcomes (KDIGO) convened a Consensus Conference with the goal of standardizing and refining the nomenclature used in the English language to describe kidney function and disease, and of developing a glossary that could be used in scientific publications. Guiding principles of the conference were that the revised nomenclature should be patient-centered, precise, and consistent with nomenclature used in the KDIGO guidelines. Conference attendees reached general consensus on the following recommendations: (i) to use "kidney" rather than "renal" or "nephro-" when referring to kidney disease and kidney function; (ii) to use "kidney failure" with appropriate descriptions of presence or absence of symptoms, signs, and treatment, rather than "end-stage kidney disease"; (iii) to use the KDIGO definition and classification of acute kidney diseases and disorders (AKD) and acute kidney injury (AKI), rather than alternative descriptions, to define and classify severity of AKD and AKI; (iv) to use the KDIGO definition and classification of chronic kidney disease (CKD) rather than alternative descriptions to define and classify severity of CKD; and (v) to use specific kidney measures, such as albuminuria or decreased glomerular filtration rate (GFR), rather than "abnormal" or "reduced" kidney function to describe alterations in kidney structure and function. A proposed 5-part glossary contains specific items for which there was general agreement. Conference attendees acknowledged limitations of the recommendations and glossary, but they considered standardization of scientific nomenclature to be essential for improving communication.

CKD: A Call for an Age-Adapted Definition

Current criteria for the diagnosis of CKD in adults include persistent signs of kidney damage, such as increased urine albumin-to-creatinine ratio or a GFR below the threshold of 60 ml/min per 1.73 m2 This threshold has important caveats because it does not separate kidney disease from kidney aging, and therefore does not hold for all ages. In an extensive review of the literature, we found that GFR declines with healthy aging without any overt signs of compensation (such as elevated single-nephron GFR) or kidney damage. Older living kidney donors, who are carefully selected based on good health, have a lower predonation GFR compared with younger donors. Furthermore, the results from the large meta-analyses conducted by the CKD Prognosis Consortium and from numerous other studies indicate that the GFR threshold above which the risk of mortality is increased is not consistent across all ages. Among younger persons, mortality is increased at GFR <75 ml/min per 1.73 m2, whereas in elderly people it is increased at levels <45 ml/min per 1.73 m2 Therefore, we suggest that amending the CKD definition to include age-specific thresholds for GFR. The implications of an updated definition are far reaching. Having fewer healthy elderly individuals diagnosed with CKD could help reduce inappropriate care and its associated adverse effects. Global prevalence estimates for CKD would be substantially reduced. Also, using an age-specific threshold for younger persons might lead to earlier identification of CKD onset for such individuals, at a point when progressive kidney damage may still be preventable.

Epidemiology of chronic kidney disease: think (at least) twice!

The introduction of the Kidney Disease: Improving Global Outcomes (KDIGO) guidelines has substantially contributed to the early detection of different stages of chronic kidney disease (CKD). Several recent studies from different parts of the world mention a CKD prevalence of between 8 and 13%. There are several reasons the CKD prevalence found in a study of a particular population is clearly overestimated. The structure of the population pyramid (young or older age) of the study sample may result in high or low CKD prevalence. The absence of using an isotope dilution mass spectrometry creatinine assay can be the source of high bias in CKD prevalence. In addition, using an arbitrary single threshold of estimated glomerular filtration rate (eGFR; <60 mL/min/1.73 m2) for classifying CKD leads to a substantial 'overdiagnosis' (false positives) in the elderly (>65 years of age), particularly in those without albuminuria (or proteinuria), haematuria or hypertension. It also results in a significant 'underdiagnosis' (false negatives) in younger individuals with an eGFR >60 mL/min/1.73 m2 and below the third percentile for their age/gender category. The use of third percentile eGFR rates as a cut-off based on age/gender-specific reference values of eGFR allows the detection of these false positives and negatives. In the present article, we focus on an important and frequently omitted criterion in epidemiological studies: chronicity. Indeed, the two most important factors introducing a high number (up to 50%) of false positives are lack of confirming proteinuria and the absence of proof of chronicity of the eGFR found at first screening. There is an urgent need for quality studies of the prevalence of CKD using representative randomized samples of the population, applying the KDIGO guidelines correctly.

Evidence-based treatment of chronic kidney disease

Chronic kidney disease is prevalent among adults in the United States. To aid in diagnosis and treatment, the Kidney Disease: Improving Global Outcomes 2012 Clinical Practice Guideline for the Evaluation and Management of Chronic Kidney Disease provides an evidence-based approach. This article reviews the major recommendations of this guideline.

Interplay between chronic kidney disease (CKD) and upper tract urothelial carcinomas (UUC): foe or friend?

Although upper tract urothelial carcinomas (UUC) is curable through nephrectomy or nephroureterectomy, progression of chronic kidney disease (CKD) and CKD-related mortality have been highlighted as clinical challenges in recent years owing to the loss of a large number of nephrons. While CKD can promote the development of UUC, other risk factors such as hypertension, diabetes mellitus, advanced age, and anemia can facilitate the progression of CKD. Conversely, CKD is especially prevalent in UUC patients. However, the relationship between CKD and UUC, mechanisms for CKD causing UUC, and gender disparity of UUC of CKD patients have so far not been well-reviewed. As UUC gradually grows, the cancer can be a physical obstacle in the urinary tract. It will cause an increased tract pressure, subsequently resulting in the dysfunction of both nephrons and kidney. At the molecular level, reduced level of oxidative stress was observed in female UUC patients. Furthermore, radical nephrectomy therapy for UUC patients accelerates the progress of chronic kidney dysfunction. Incidentally, the remedies for CKD containing aristolochic acid (AA) are carcinogenic. Our present review offers a comprehensive look at the relationship between CKD and UUC from multiple perspectives. Early and precise identification of progression of CKD and UUC will benefit the patients at high-risk of CKD or UUC, which will also be instructive in directing timely and effective therapeutic interventions whenever necessary. It may also shed light on unveiling the underlying mechanisms of carcinogenesis of UUC, preventing CKD progression, and prolonging the patients' overall survival.

High-performance information search filters for CKD content in PubMed, Ovid MEDLINE, and EMBASE

BACKGROUND

Finding relevant articles in large bibliographic databases such as PubMed, Ovid MEDLINE, and EMBASE to inform care and future research is challenging. Articles relevant to chronic kidney disease (CKD) are particularly difficult to find because they are often published under different terminology and are found across a wide range of journal types.

STUDY DESIGN

We used computer automation within a diagnostic test assessment framework to develop and validate information search filters to identify CKD articles in large bibliographic databases.

SETTING & PARTICIPANTS

22,992 full-text articles in PubMed, Ovid MEDLINE, or EMBASE.

INDEX TEST

1,374,148 unique search filters.

REFERENCE TEST

We established the reference standard of article relevance to CKD by manual review of all full-text articles using prespecified criteria to determine whether each article contained CKD content or not. We then assessed filter performance by calculating sensitivity, specificity, and positive predictive value for the retrieval of CKD articles. Filters with high sensitivity and specificity for the identification of CKD articles in the development phase (two-thirds of the sample) were then retested in the validation phase (remaining one-third of the sample).

RESULTS

We developed and validated high-performance CKD search filters for each bibliographic database. Filters optimized for sensitivity reached at least 99% sensitivity, and filters optimized for specificity reached at least 97% specificity. The filters were complex; for example, one PubMed filter included more than 89 terms used in combination, including "chronic kidney disease," "renal insufficiency," and "renal fibrosis." In proof-of-concept searches, physicians found more articles relevant to the topic of CKD with the use of these filters.

LIMITATIONS

As knowledge of the pathogenesis of CKD grows and definitions change, these filters will need to be updated to incorporate new terminology used to index relevant articles.

CONCLUSIONS

PubMed, Ovid MEDLINE, and EMBASE can be filtered reliably for articles relevant to CKD. These high-performance information filters are now available online and can be used to better identify CKD content in large bibliographic databases.

Understanding the mechanisms of proteinuria: therapeutic implications

A large body of evidence indicates that proteinuria is a strong predictor of morbidity, a cause of inflammation, oxidative stress and progression of chronic kidney disease, and development of cardiovascular disease. The processes that lead to proteinuria are complex and involve factors such as glomerular hemodynamic, tubular absorption, and diffusion gradients. Alterations in various different molecular pathways and interactions may lead to the identical clinical end points of proteinuria and chronic kidney disease. Glomerular diseases include a wide range of immune and nonimmune insults that may target and thus damage some components of the glomerular filtration barrier. In many of these conditions, the renal visceral epithelial cell (podocyte) responds to injury along defined pathways, which may explain the resultant clinical and histological changes. The recent discovery of the molecular components of the slit diaphragm, specialized structure of podocyte-podocyte interaction, has been a major breakthrough in understanding the crucial role of the epithelial layer of the glomerular barrier and the pathogenesis of proteinuria. This paper provides an overview and update on the structure and function of the glomerular filtration barrier and the pathogenesis of proteinuria, highlighting the role of the podocyte in this setting. In addition, current antiproteinuric therapeutic approaches are briefly commented.

Renal function after nephron-sparing surgery for renal tumors

Nephron sparing surgery (NSS) is a technique more frequently utilized in the case of surgical treatment of kidney tumor. The aim of the study is to assess renal function in patients treated with NSS for renal tumors. Twenty patients, after NSS performed for renal tumor, were included in the study. In each patient dynamic renal scintigraphy was performed before surgical treatment (test No. 1) and after a mean interval of 12 months after surgical procedure (test No. 2). In each test renographic curves were evaluated. Creatinine levels and GFR rates were also assessed. Mean GFR was 84 ml/min/1.73 m(2) before surgery, and 79 ml/min/1.73 m(2) after surgical procedure. Mean change of GFR value after the surgical procedure was -5.1 (p >0.058). On renography significant deterioration of renal function was observed in the operated kidneys of 4 patients (20%) after NSS, insignificant deterioration - in four patients (20%) and improvement of renal function of operated kidney was found in one patient. In 12 patients (60%) no change was observed. The relative percentage GFR-share of operated kidney decreased by the average value of 3.8% (p >0.005). Multifactorial analysis did not identify significant effect of potential risk factors on the function of the kidney subjected to NSS. Preliminary results of this study confirm that deterioration of renal function after NSS is a rare event.

Relationship between chronic kidney disease and risk of coronary heart disease in Korean men

There have been many epidemiological researches of chronic kidney disease (CKD), accompanied by an increase in the incidence of coronary heart disease (CHD). However, as far as we know, little research has been done to examine the extent of the relationship between CKD and CHD as estimated by Framingham risk score (FRS) in Korean men. CKD was defined as either proteinuria or an eGFR of < 60 mL/min per 1.73 m(2). The FRS has been used to predict the 10-yr risk of coronary events and usually divided into three levels of risk < 10% (low), 10%-19% (intermediate) and ≥ 20% (high). We defined FRS ≥ 10% as more-than-a-moderate CHD risk group and FRS ≥ 20% as a high CHD risk group, respectively. After adjusting for covariates, multivariable-adjusted logistic regression analyses showed a strong statistical significant relationship between CKD and high risk of CHD (adjusted OR, 1.95 [95% CI, 1.32-2.87]). Dipstick urinalysis and eGFR can be readily measured in most clinical settings. The measurement of kidney function may represent a relatively inexpensive and efficient way to identify individuals at higher risk for CHD.

Definition of chronic kidney disease and measurement of kidney function in original research papers: a review of the literature

BACKGROUND

Over the past decade, chronic kidney disease (CKD) has become an area of intensive clinical and epidemiological research. Despite the clarity provided by the Kidney Disease Outcomes Quality Initiative (KDOQI) guidelines, there appears to be within the CKD research literature significant disagreement on how to define CKD and measure kidney function.

METHODS

The objectives of this study were to investigate the variety of methods used to define CKD and to measure kidney function in original research papers as well as to investigate whether the quality of the journal had any effect on the quality of the methodology used. This was a descriptive review and not a meta-analysis. Information was extracted from each article including publication details (including the journal's impact factor), definition of CKD, method used to estimate kidney function and quantity of serum creatinine readings used to define CKD. An electronic search of MEDLINE through OVID was completed using the search term CKD. The search was limited to articles in English published in 2009. Studies were included in the review only if they were original research articles including patients with CKD. Articles were excluded if they reported data from a paediatric population, a population solely on dialysis or if there was no full-text access through OVID. Each article was assessed for quality with respect to using KDOQI CKD definition criteria. A description of the pooled data was completed and chi-square tests were used to investigate the relation between article quality and journal quality. Analysis was carried out using SPSS (15.0) and a P-value of <0.05 was considered to indicate statistical significance.

RESULTS

The final review included 301 articles. There were a variety of methods used to define CKD in original research articles. Less than 20% (n = 59) of the articles adhered to the established international criteria for defining CKD. The majority of articles (52.1%) did not indicate the quantity of serum creatinine measurements used to define CKD. The impact factor or specialist nature of the scientific journal appears to have no bearing on whether or not published articles use the gold standard KDOQI guidelines for labelling a patient with a diagnosis of CKD.

CONCLUSIONS

This review of literature found that a variety of definitions are being used in original research articles to define CKD and measure kidney function which calls into question the validity and reliability of such research findings and associated clinical guidelines. International consensus is urgently required to improve validity and generalizability of CKD research findings.

Optimal search filters for renal information in EMBASE

BACKGROUND

EMBASE is a popular database used to retrieve biomedical information. Our objective was to develop and test search filters to help clinicians and researchers efficiently retrieve articles with renal information in EMBASE.

STUDY DESIGN

We used a diagnostic test assessment framework because filters operate similarly to screening tests.

SETTINGS & PARTICIPANTS

We divided a sample of 5,302 articles from 39 journals into development and validation sets of articles.

INDEX TEST

Information retrieval properties were assessed by treating each search filter as a "diagnostic test" or screening procedure for the detection of relevant articles. We tested the performance of 1,936,799 search filters made of unique renal terms and their combinations. REFERENCE STANDARD & OUTCOME: The reference standard was manual review of each article. We calculated the sensitivity and specificity of each filter to identify articles with renal information.

RESULTS

The best renal filters consisted of multiple search terms, such as "renal replacement therapy," "renal," "kidney disease," and "proteinuria," and the truncated terms "kidney," "dialy," "neph," "glomerul," and "hemodial." These filters achieved peak sensitivities of 98.7% (95% CI, 97.9-99.6) and specificities of 98.5% (95% CI, 98.0-99.0). The retrieval performance of these filters remained excellent in the validation set of independent articles.

LIMITATIONS

The retrieval performance of any search will vary depending on the quality of all search concepts used, not just renal terms.

CONCLUSIONS

We empirically developed and validated high-performance renal search filters for EMBASE. These filters can be programmed into the search engine or used on their own to improve the efficiency of searching.