ABSTRACT The incidence and prevalence of patients with acute kidney injury and chronic kidney disease have increased significantly in recent years. Renal failure is associated with profound changes in the pharmacokinetics and pharmacodynamics of antibiotics. It is widely recognized that inadequate adjustment of antibiotics can lead to undertreatment and impair the patient’s clinical outcome. The difficulty of adjusting drugs in renal dysfunction begins with estimating renal function (urinary clearance of inulin is rarely performed, and creatinine/cystatin-based formulas have widely recognized limitations, especially in acute kidney injury). Management becomes more complex, given the frequent changes in the volume of distribution and the introduction of different renal replacement therapies. Efforts must be made to optimize antibiotic targets in this population. This study aims to review the principal pharmacokinetic and pharmacodynamic modifications that occur with antibiotics in chronic kidney disease and acute kidney injury, with the goal of offering strategies to enhance antibiotic therapy in these scenarios.

ABSTRACT Antineutrophil cytoplasmic antibodies (ANCA) are useful as markers for systemic vasculitis. PR3-ANCA antibodies have been also identified in association with chronic inflammatory and infectious conditions, other autoimmune diseases, malignancy, and certain drugs. The association of PR3 and minimal change disease (MCD) without vasculitis is not an expected finding. We report a case of MCD with PR3-ANCA positive title and no histopathological findings of vasculitis. This reports to an 86-year-old Caucasian woman without relevant past medical history and a normal renal function one month before presentation with sudden-onset nephrotic syndrome and rapidly progressive renal failure. Renal ultrasound was normal. Autoimmune screening using enzyme-linked immunosorbent assay (ELISA) revealed PR3-ANCA high titers (238.7UQ). Renal biopsy did not show vasculitis or crescentic glomerulonephritis. The glomeruli were normal. Autoimmune, inflammatory, infectious and malignant diseases were excluded. MCD was assumed and she started prednisolone with clinical and analytical improvement. ANCA-associated glomerular disease can coexist with a variety of other glomerular diseases including membranous nephropathy, lupus nephritis, IgA nephropathy, and bacterial infection-related glomerulonephritis. This association could be an incidental finding, but there may be an association with MCD not previously reported. Our case emphasizes the importance of performing renal biopsies before embarking on a full-scale immunosuppression therapy based on ANCA title alone.

RESUMO Introdução: A taxa estimada de filtração glomerular (TFGe) com base na cistatina-C sérica (Cis-C) parece ser tão precisa quanto aquela baseada na creatinina sérica (Cr), mas cis-C parece ser um melhor preditor de resultados adversos. Nosso objetivo foi avaliar se a cis-C poderia ser uma ferramenta confiável para a previsão de desfechos adversos em pacientes idosos com doença renal crônica grave (DRC). Métodos: Um grupo de 348 pacientes idosos com DRC em estágio não terminal (estágios 1-4, de acordo com TFGe-EPI Cr e/ou Cis-C), encaminhados para nossa unidade de consulta durante 2016, foi estudado retrospectivamente e dividido em quatro categorias exclusivas: DRC_estágio 4 nenhum (TFGe-Cr≥30mL/min; TFGe -Cis-C≥30mL/min), DRC_estágio 4_Cr apenas (TFGe-Cr <30mL/min), DRC_estágio 4 _Cis-C_apenas (TFGe-Cis-C <30 mL/min), DRC_estágio4_combinado (TFGe-Cis-C <30mL/min. TFGe-Cr <30mL/min). Características basais, preditores de óbito e eventos clínicos (eventos cardiovasculares e internações por doenças cardiovasculares, lesão renal aguda ou eventos infecciosos) foram explorados até dezembro de 2018. Resultados: Uma coorte de 77 ± 7,4 anos, com índice de comorbidade de Charlson modificado (mCCI) de 3 (IQR: 1-4), foi acompanhada durante 29 (IQR: 26-33) meses. Não houve diferenças significativas entre as características dos grupos no estágio 4. A análise de sobrevida foi estratificada pelo acompanhamento aos 12 meses, sendo que no primeiro ano, as curvas de sobrevida dos grupos DRC_estágio4_Cis-C_apenas e DRC_estágio4_ combinado foram significativamente inferiores quando comparadas com os restantes grupos (p = 0,028). Ajustando para idade, sexo e mCCI, DRC_estágio4_Cis-C_apenas, ao contrário do grupo DRC_estágio4_Cr_apenas, teve maiores taxas de eventos clínicos (p <0,05) do que o grupo DRC_estágio4_nenhum. Conclusão: Em pacientes idosos com estadiamento discordante da DRC, a TFGe baseada na Cis-C parece ser um melhor preditor de resultados adversos do que a TFGe baseada na Cr. Pacientes com DRC em estágio 4, definida apenas por Cr, parecem se comportar de forma semelhante àqueles com DRC menos grave.

ABSTRACT Introduction: Estimated glomerular filtration rate (eGFR) based on serum cystatin-C (sCys) seems as accurate as when based on serum creatinine (sCr), but sCys seems a better predictor of adverse outcomes. We aimed to study whether sCys could be a reliable tool for the prediction of adverse outcomes in elderly patients with severe chronic kidney disease (CKD). Methods: A group of 348 elderly patients with non-end-stage CKD (stages 1-4, according to eGFR-EPI sCr and/or sCys), referred to our consultation unit during 2016, was retrospectively studied and divided into four exclusive categories: CKD_stage4_neither (eGFR-sCr≥30mL/min; eGFR-sCys≥30mL/min), CKD_stage4_sCr_only (eGFR-sCr<30mL/min), CKD_stage4_sCys_only (eGFR-sCys<30mL/min) and CKD_stage4_combined (eGFRsCr<30mL/min; eGFR-sCys<30mL/min). Baseline characteristics, predictors of death, and clinical events (cardiovascular events and admissions for cardiovascular, acute kidney injury or infectious events) were explored until December 2018. Results: A 77±7.4 year-old cohort, with a modified Charlson Comorbidty Index (mCCI) of 3 (IQR:1-4), was followed-up during 29 (IQR: 26-33) months. There were no significant differences between the characteristics of the stage 4 groups. Survival analysis was stratified by follow-up at 12 months, and in the first year, survival curves of CKD_stage4_sCys_only and CKD_stage4_combined groups were significantly lower than the other groups (p=0.028). Adjusting for age, sex, and mCCI, CKD_stage4_sCys_only, conversely to CKD_stage4_sCr_only, had higher rates of clinical events (p<0.05) than CKD_stage4_neither group. Conclusion: In elderly patients with discordant CKD staging, sCys-based eGFR seems to be a better predictor of adverse outcomes than sCr-based eGFR. Patients with stage 4 CKD defined by sCr alone seem to behave similar to those with less severe CKD.

Background and objectives: To evaluate RRT benefits and risks and to inform patients and their families about ESRD treatment options, we have developed a prognostic score to predict 6-month mortality in elderly ESRD patients initiating dialysis. Five independent predictors were identified and a point system was constructed: age 75 years or older (2 points), coronary artery disease (2 points), cerebrovascular disease with hemiplegia (2 points), time of nephrology care before dialysis [< 3.0 months (2 points); ≥ 3 to < 12 months (1 point)], serum albumin levels [3.0 - 3.49 g/dL (1 point); < 3.0 g/dL (2 points)]. Model performance was good in both discrimination and internal validation. Before adopting our risk score into practice, our aim is to externally validate this initial predictive model by assessing its performance on a new data set. Methods: We apply the predictive score developed in a cohort of CKD patients, aged 65 years and over who started dialysis between 2009 and 2016, to an independent cohort of ESRD patients, aged 65 years and over who started dialysis between 2017 and 2019, in our Nephrology department. The performance of the prediction equation created in development cohort, was assessed using discrimination and calibration metrics in the validation cohort. Results: Our validation study cohort included 168 individuals, with a mortality rate of 12.5% (n=21) within 6-months of dialysis initiation. Model performance in the validation cohort had an acceptable discrimination [AUC of 0.79; (95% confidence interval, 0.70 to 0.88)]. The Hosmer and Lemeshow goodness-of-fit test was not statistically significant, indicating good calibration of the model (χ2, 5 degrees of freedom = 2.311; P = 0.805). Conclusions: Our predictive simple score based on readily available clinical and laboratory data demonstrates a good performance when externally validated, namely with respect to discrimination and calibration. Model validation is crucial for adequately informing patients and their families about ESRD treatment options and providing a more patient-centered overall approach to care. Before we start general implementation in clinical practice, our score needs further validation in larger patient cohorts.

Introduction: Vascular access (VA) for hemodialysis (HD) is the lifeline for End Stage Renal Disease (ESRD) patients. Long-term HD patients often have exhaustion of their venous patrimony for an autologous VA construction and, sometimes, even for a central venous catheter (CVC) placement. Case report: We describe the case of a 43-year-old woman with ESRD due to lupus nephritis, on maintenance HD since 2009. She also had secondary antiphospholipid syndrome and was chronically anticoagulated. Nevertheless, the patient had multiorgan thrombotic events (without sequelae) and several episodes of irreversible thrombosis of arteriovenous fistulas. Her HD course was also marked by multiple severe CVC infections, at different locations; a hemoperitoneum during cholecystectomy, and an immediate thrombosis of the renal artery of a kidney transplant. She was admitted to our hospital after an irreversible dysfunction of a right jugular CVC, with documentation of thrombosis of the superior and inferior vena cava. Exhaustion of the venous patrimony for HD was assumed and it was decided to make an arterio-arterial graft (AAG) of early cannulation. The first cannulation of the AAG was performed two days after surgical intervention, with no complications. The patient performed a twelve hour per week HD treatment with good efficiency. Conclusion: AAG is an alternative for HD patients who have exhausted all their venous patrimony and it can be considered prior to the placement of a CVC as their sole remaining vascular access.

Among thrombotic microangiopathies (TMA), the hemolytic uremic syndrome associated with dysregulation of the alternative complement pathway (aHUS) is one of the most challenging diseases a nephrologist can face. By the end of the XXth century, the complement’s role was unraveled with the discovery that mutations in the factor H coding gene were responsible for aHUS. But it was the acknowledgment that pharmacological C5-9 blockage provided a cure for aHUS that fostered the interest of the nephrology community in the genetics, pathophysiology and therapeutics of, not only of aHUS, but TMA in general. The molecular genetics of aHUS is technically demanding and, as such, in Portugal (alike many other European countries) a single laboratory emerged as a national reference center. The fact that all samples are evaluated in a single center provides a unique opportunity for data collection and a forum for discussion for all those interested in the field: immunologists, molecular geneticists, pathologists and nephrologists. The current consensus document emerged from such a discussion forum and was sponsored by the Portuguese Society of Nephrology. The goal is more to portray the Portuguese picture regarding the diagnostic approach and therapeutic options than to extensively review the state of the art of the subject. The accompanying documents that are published as supplementary data are in line with that goal. They range from the informed consent and clinical form to be sent together with the biological samples for genetic testing, to the appendix regarding the actual sampling and storing conditions. The document is also intended to set an example for future documents and independent discussion forums on other kidney diseases for which emerging diagnostic and/or therapeutic strategies are reaching clinical practice

Tubulointersticial nephritis and uveitis syndrome is an idiopathic and rare cause of acute kidney injury that should not overlooked, because it usually requires specific therapeutic interventions. We report two distinct cases: a young and an elder female. Both cases presented with unspecific constitutional symptoms but had different onset of renal and ocular involvement. Both were treated with topical and systemic corticoids and although there was a good initial response in both cases, an early relapse after steroids taper was observed in the younger patient and a persistent renal dysfunction in the older one. A high clinical suspicion and understanding of this disease is necessary for an adequate management and treatment of these patients. Recent data associates a worse renal prognosis when the disease appears inadvanced age. In both of our cases the outcome was good but we had a short follow-up. The histological presentation of this disease in our older patient was similar to that reported in the literature, with a high percentage of fibrosis and chronicity of renal tissue that can contribute to the higher grade of renal dysfunction in this type of patients

Monoclonal gammopathies are a heterogeneous group of disorders characterized by clonal proliferation of immunoglobulin produced by B-lymphocytes or plasma cell clone. The term monoclonal gammopathy of renal significance (MGRS) was introduced to distinguish monoclonal gammopathies that result in the development of kidney disease from those that are benign. Screening for monoclonal immunoglobulin and an appropriate hematologic workup are fundamental and sometimes a difficult challenge, with therapeutic and prognostic implications. Kidney biopsy is essential to determine the exact nature of the lesion and to evaluate the severity of renal disease. In this review we discuss the clinical and pathologic features of MGRS, highlighting the most diagnostic difficulties and current therapeutic options

RESUMO Introdução: a vasculite associada aos anticorpos anticitoplasma de neutrófilos (ANCA) é uma doença autoimune que pode acometer vários órgãos, sendo o rim um dos mais afetados. Além dos ANCA serem marcadores de diagnóstico, foram também defendidos como marcadores de atividade. Recentemente as alterações genéticas encontradas entre as poliangeítes serina-protease 3 da proteinase (PR3)-ANCA ou mieloperoxidase (MPO)-ANCA levantam a possibilidade de diferenças imunopatogênicas e terapêuticas. Objetivos: identificar diferenças quanto a número de recidivas, marcadores inflamatórios, desfechos e histologia renal relativamente aos tipos de ANCA. Analisar implicações dos títulos de ANCA no prognóstico. Método: estudo retrospectivo observacional em hospital terciário português. Resultados: não se verificaram diferenças quanto à evolução da função renal, ao padrão histológico e ao tratamento inicial relativamente aos subtipos de ANCA. Nos parâmetros analíticos avaliados, não se verificaram diferenças significativas relativas aos tipos de ANCA, à exceção do valor médio de PCR no intervalo que foi de 6,3±1,3 mg/L nos MPO-ANCA e 12,4±10,14 mg/L nos PR3-ANCA (p=0,04). Verificamos que 66,7% dos MPO-ANCA positivos não apresentaram recidivas versus 40% dos PR3-ANCA positivos. Não se verificou nenhuma correlação entre os títulos de ANCA à apresentação, durante a remissão e na última avaliação com o número de recidivas. Conclusão: os indivíduos PR3-ANCA apresentaram um valor médio de PCR nos intervalos superior aos indivíduos MPO-ANCA (p=0,04), o que parece evidenciar uma maior atividade inflamatória nos primeiros.

SUMMARY Introduction: Anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitis is an autoimmune disease that can affect multiple organs, the kidney being one of the most affected. Apart from the diagnostics value of ANCA, they have also been advocated as biomarkers of the disease activity. Recently, the genetic changes found in polyangiitis associated with serine-protease proteinase 3 (PR3)-ANCA or myeloperoxidase (MPO)-ANCA raised the possibility of immune-pathogenic and therapeutic differences. Objective: To identify differences in the number of relapses, inflammatory markers, outcomes and renal histology related to the types of ANCA. To analyze the implications of ANCA titers in prognosis. Method: A retrospective observational study in a Portuguese tertiary hospital. Results: There were no differences in the progression of renal function, histological pattern and initial treatment with regard to ANCA subtypes. As for the evaluated parameters, there were no significant differences according to the types of ANCA, except for mean CRP values within the normal range, which was 6.3±1.3 mg/L for MPO-ANCA and 12.4±10.14 mg/L for PR3-ANCA (p=0.04). We found that 66.7% of the MPO-ANCA-positive showed no relapses versus 40% in the case of PR3-ANCA-positive. There was no correlation between the ANCA titers at presentation, during remission, and in the last evaluation, and the number of relapses. Conclusion: PR3-ANCA patients have a mean CRP value within the normal range significantly higher than that of MPO-ANCA patients (p=0.04), which seems to reveal greater inflammatory activity in the first.

A doença inflamatória intestinal e as terapêuticas que lhe estão associadas podem afetar o rim de várias formas. A nefrite tubulointersticial é uma complicação rara, mas potencialmente grave inerente à terapêutica com mesalazina. Há alguns casos descritos na literatura. Os autores descrevem os dois primeiros casos de nefrite tubulointersticial associados ao uso de mesalazina, recentemente diagnosticados no nosso Serviço; um deles num doente com colite ulcerosa, outro num doente com doença de Crohn. Apresentam uma revisão da literatura sobre o atingimento renal na doença inflamatória intestinal. Os casos de nefrotoxicidade associada à mesalazina devem continuar a ser descritos para permitir estabelecer uma incidência mais precisa desde efeito adverso. A monitorização da função renal durante o tratamento é simples, barata e pode ajudar a diagnosticar precocemente esta complicação

Inflammatory bowel disease and its various treatments may affect the kidney in several ways. Tubulointersticial nephritis is a rare but serious complication of longer-term mesalazine use. There are few cases reported in the literature. We report the first two cases of mesalazine-induced tubulointersticial nephritis, recently diagnosed in our department. The first one refers to a patient with ulcerous colitis and the second one to a patient with Crohn’s disease. Then the authors present a review of literature about the renal involvement in the inflammatory bowel disease. New cases of mesalazine nephrotoxicity should be reported to allow more accurate incidence estimation of this serious adverse effect. Routine monitoring of renal function is simple, inexpensive and allows an early diagnosis of this complication

O envolvimento renal nas vasculites associadas aos anticorpos anticitoplasma de neutrofilos (ANCA) e frequente e, na ausencia de resposta ao tratamento, evoluem rapidamente para doenca renal terminal, com aumento da mortalidade. Avaliamos varios fatores (clinicos, analiticos e histologicos) como preditores da evolucao para Doenca Renal Cronica Estadio 5 com necessidade de dialise aos 2 anos em doentes com envolvimento renal por vasculite ANCA confirmado por biopsia (“outcome”) entre 1997 e 2010. Vinte e sete doentes (16 do sexo masculino, idade media de 58 anos) obedeceram aos criterios de inclusao. As manifestações extra-renais mais frequentes foram hematologicas (93%) e sintomas sistemicos (70%). A data da biopsia a creatinina e a proteinuria media eram 5,11 �± 2,5mg/dL e 2,36 ± 2,1g/dia, respectivamente. A maioria dos doentes (81%) tinha ANCA contra mieloperoxidase. A terapeutica de inducao foi em 71% com corticoides e ciclofosfamida; 40% receberam tratamento de manutencao com azatioprina. Aos 2 anos, 12 (27,44%) iniciaram tecnicas de substituicao renal (TSR). Apenas a creatinina mais elevada a apresentacao, dentro das variaveis clinicas e analiticas, foi preditor significativo de “outcome” (odds ratio (OR) = 1,73; p = 0,046), num modelo de regressao logistica ajustado para a idade e sexo. Desenvolvemos um indice histológico (0 ou 1 ponto considerando a presenca de: < 30% de glomerulos normais, > 50% crescentes celulares, > 30% glomerulosclerose, infiltrado intersticial e atrofia tubular moderados-graves), que se associava com o prognostico renal aos 2 anos (OR = 2,07, p = 0,043). Isto significa que, por cada aumento de 1 ponto no indice criado, a probabilidade de necessidade de TSR aos 2 anos torna-se 2,1 vezes maior. Depois estratificamos as variaveis histologicas em achados glomerulares e tubulointersticiais: verificamos que apenas os primeiros eram preditivos do prognostico (OR = 4,99, p =0,049), sendo a glomerulosclerose a mais significativa (OR = 16,07, p = 0,04). Concluiu-se que a creatinina e os achados histologicos glomerulares sao preditores independentes do prognostico renal, podendo mostrar-se uteis no acompanhamento destes doentes.

Renal involvement in antineutrophil cytoplasmic antibodies (ANCA) associated vasculitis is frequent and, if there is no response to treatment, progression to end-stage renal disease is fast, leading to increased mortality. We evaluated several factors (clinical, analytical and histological) as predictors of progression to dialysis-dependent stage 5 chronic kidney disease within 2 years after diagnosis of kidney biopsy-proven ANCA-associated vasculitis (outcome), between 1997 and 2010. Twenty-seven patients (16 men, mean age 58 years) met the inclusion criteria. The most common extra-renal manifestations were haematological (93%) and systemic symptoms (70%). At the time of biopsy, mean creatinine and proteinuria were 5.11 �± 2.5mg/dL and 2.36 �± 2.1g/day, respectively. The majority of patients (81%) had ANCA against myeloperoxidase. The induction therapy was with corticosteroids and cyclophosphamide in 71%; 40% received maintenance treatment with azathioprine. At 2 years, 12 patients (27.44%) began renal replacement therapy (RRT). Only a higher serum creatinine at diagnosis, within the clinical and analytical variables analysed, was a significant predictor of renal outcome (odds ratio (OR) = 1.73, p = 0.046) in a logistic regression model adjusted for age and sex. We developed a histological index (0 to 1 point considering the absence or presence of: < 30% of normal glomeruli, > 50% cellular crescents, > 30% glomerulosclerosis, moderate-severe tubular atrophy and interstitial infiltrate), which was associated with renal prognosis at 2 years (OR = 2.07, p = 0.043). This means that for each 1-point increase in the created index the likelihood of needing to RRT to 2 years rises 2.1 times. We then stratified the histological variables into glomerular and tubulointerstitial findings. We found that only the glomerular findings (OR = 4.99, p = 0.049) were independent predictors of the outcome, with glomerulosclerosis (OR = 16.7, p = 0.04) being the most significant. We concluded that baseline serum creatinine and glomerular histological findings were independent predictors of the renal prognosis and may prove helpful in the management of these patients.

O diagnóstico de doença renal crónica tem aumentado na população idosa, embora o seu significado clínico seja ainda debatido. A creatinina sérica e cistatina C são os marcadores endógenos de função renal mais utilizados. Várias equações, ajustadas para variáveis demográficas, foram derivadas destes marcadores com o objectivo de estimar o débito do filtrado glomerular. O valor de creatinina sérica é influenciado pela massa muscular pelo que, nos indivíduos com redução da massa muscular como é o caso dos idosos, tende a sobrestimar a função renal. Por outro lado, a cistatina C parece melhorar a estimativa da função renal nos idosos, embora o melhor desempenho tenha sido observado com as equações que incluem ambos os marcadores. A creatinina é mais utilizada do que a cistatina C, sendo as equações MDRD e EPI derivadas da creatinina, as mais usadas. Foi demonstrado que a equação EPI melhora significativamente a estimativa do débito de filtrado glomerular na população sem ou com disfunção renal ligeira, sem comprometer o seu desempenho em indivíduos com doença renal crónica avançada. Mais ainda, estudos epidemiológicos mostraram que a utilização da equação EPI permitia uma identificação mais relevante dos doentes com doença renal crónica. Contudo, na população idosa não devemos enfatizar demasiado a necessidade de uma estimativa exata da filtração glomerular, mas sim avaliar a probabilidade de progressão da disfunção renal, tendo em conta o risco competitivo entre doença renal crónica terminal e morte. Vários estudos demonstraram que as equações derivadas da cistatina C (com ou sem creatinina) têm uma melhor capacidade preditiva, relativamente às equações derivadas unicamente da creatinina, no que se refere aos eventos cardiovasculares e à morte. Relativamente à doença renal crónica terminal os resultados são mais controversos, embora uma metanálise recente mostrou que na população idosa as equações derivadas da cistatina C apresentam o melhor valor preditivo. Assim, sublinhamos a necessidade de uma utilização individualizada destas equações na população idosa, na qual estas devem ser valorizadas não tanto pela precisão da sua estimativa de função, mas mais como preditoras de eventos clínicos, permitindo que a sua utilização seja mais criteriosa e clinicamente relevante.

Chronic kidney disease (CKD) has been increasingly diagnosed in the elderly, though its clinical significance is still matter of debate. Serum creatinine and cystatin C are the most used endogenous renal function markers. Several equations, usually adjusted for demographical variables, have been derived from them, in order to estimate glomerular filtration rate (eGFR). Serum creatinine levels are influenced by muscle mass so, in patients frequently sarcopenic as the elderly, tends to overestimate renal function. Differently, serum cystatin C seems to improve kidney function estimation in the elderly, although the best performance results have been obtained with equations that include both markers. Creatinine is more widely used than cystatin C, with MDRD and EPI being the most common creatininebased equations. The EPI equation has been shown to improve significantly GFR estimation in subjects with no or mild kidney dysfunction, without jeopardizing eGFR performance in subjects with advanced CKD. Moreover, epidemiological studies have shown that EPI equation may allow a more clinically relevant identification of chronic kidney disease patients. Nevertheless, in the elderly population, one should not overemphasize the issue of GFR accurate estimation, but rather appreciate the probability of kidney dysfunction progression, taking into account the competitive risk between end-stage renal disease and death. Several studies have demonstrated that cystatin C-based (with or without creatinine) equations have considerable better prediction ability than creatinine-only based equations, particularly for death and cardiovascular events. Considering end-stage renal disease, results are more conflicting, although a recent meta-analysis has shown that in the elderly population cystatin C-based equations presented the best predictive behaviour. Thus, we stress the need for an individualized use of glomerular filtration rate equations in the elderly, in whom they should be regarded less as accurate estimators, but more as predictors of clinical outcomes, allowing for their use to be more judicious and clinically relevant.