In-vivo techniques for determining nephron number Purpose of review Many studies have suggested low nephron endowment at birth contributes to the risk of developing hypertension and chronic kidney disease (CKD) later in life. Loss of nephrons with age and disease is largely a subclinical process. New technologies are needed to count nephrons as glomerular filtration rate (GFR) is a poor surrogate for nephron number. Recent findings Cortical volume, glomerular density, and percent globally sclerotic glomeruli are imperfect surrogates for nephron number. The disector–fractionator method is the most accurate method to count nephrons but is limited to autopsy settings. Glomerular density combined with kidney imaging and ultrafiltration coefficient-based methods require a kidney biopsy, and have been applied in living humans (kidney donors). Low nephron number predicts a higher postdonation urine albumin. Contrast-enhanced MRI has detected glomeruli without a biopsy, but so far, not in living humans. Summary Currently, there is no accurate and well tolerated method for determining nephron number in living humans. A clinically useful method may allow GFR to be replaced by its more relevant determinants: nephron number and single nephron GFR. This could revolutionize nephrology by separating the measurement of chronic disease (nephron loss) from more reversible hemodynamic effects (nephron hyperfiltration/hypofiltration). Correspondence to Andrew D. Rule, Mayo Clinic 200 1st St SW, Rochester, MN 55905, USA. Tel: +1 507 266 1045; fax: +1 507 266 7891; e-mail: rule.andrew@mayo.edu Copyright © 2019 Wolters Kluwer Health, Inc. All rights reserved.

Current opinions in nephrology and hypertension: kidney transplantation in patients with plasma cell dyscrasias Purpose of review Plasma cell dyscrasias encompass a group of hematological disorders characterized by increased production of immunoglobulins by clonal B cells. Kidney involvement is common. Significant advances in the treatment of plasma cell dyscrasias have resulted in improved survival and may permit kidney transplantation in candidates previously denied transplantation. Treatments may also have effects on kidney transplant recipients who develop plasma cell dyscrasias post transplantation. Recent finding The available evidence suggests that transplantation of candidates with nonmultiple myeloma plasma cell dyscrasias provides good outcome with low recurrence rates, so long as the disease has been treated with a complete or good partial response prior to transplantation. Candidates with a history untreated MGRS or a history of multiple myeloma have a high rate of recurrence posttransplant. Kidney transplant recipients who develop plasma cell dyscrasias post transplantation have an increased risk of death and thalidomide-based regimens may increase the risk of rejection. Summary Transplant candidates with a history of plasma cell dyscrasia who are in remission should not be excluded from transplantation. Individuals with multiple myeloma have a high rate of recurrence and myeloma post kidney transplant must be managed carefully. Correspondence to Erik L. Lum, MD, Connie Frank Kidney Transplant Center, 200 Medical Plaza, Ste 565, Los Angeles, CA 90095, USA. Tel: +1 310 267 0552; e-mail: elum@mednet.ucla.edu Copyright © 2019 Wolters Kluwer Health, Inc. All rights reserved.

Hemodialysis care for undocumented immigrants with end-stage renal disease in the United States Purpose of review Across the United States, significant variation exists in the provision of care of undocumented immigrants with end-stage renal disease (ESRD), with some states providing standard dialysis, and other states providing emergency-only hemodialysis (EoHD). Recent findings EoHD is associated with higher morbidity and mortality compared with standard hemodialysis. EoHD is also associated with higher healthcare utilization, resulting in more emergency department visits, more days spent in the hospital, and higher healthcare costs. Undocumented immigrants with ESRD who rely on EoHD also experience crippling and potentially fatal physical symptoms as well as psychosocial suffering, with some patients describing recurrent near-death experiences. Clinicians who provide EoHD to undocumented patients report experiencing moral distress and symptoms of professional burnout because of providing care that they perceive as unethical and far below the standard of care. Summary Undocumented immigrants with ESRD who rely on EoHD have worse health outcomes and quality of life compared with patients who receive standard hemodialysis. EoHD is also more costly to the healthcare system. Healthcare policy reform is critical as more research demonstrates the worse clinical outcomes and higher costs of EoHD. Correspondence to Lilia Cervantes, MD, Department of Medicine, Denver Health and Hospital Authority, 601 Broadway, MC 4000, Denver, CO 80204-4507, USA. Tel: +1 303 602 5075; e-mail: Lilia.Cervantes@ucdenver.edu Copyright © 2019 Wolters Kluwer Health, Inc. All rights reserved.

Can incremental haemodialysis reduce early mortality rates in patients starting maintenance haemodialysis? Purpose of review Early mortality rates after the start of maintenance haemodialysis therapy are high. Compared with three-times weekly haemodialysis, incremental haemodialysis is associated with better preservation of residual renal function (RRF) and at least equivalent mid-term to long-term survival. However, there is paucity of data in relation to its use as a means of helping patients through the transitional period, when they first become dialysis dependent. Recent findings Studies of incremental haemodialysis have overlooked early mortality as an outcome measure. This is primarily due to their retrospective design which makes it difficult to link early deaths to the frequency of haemodialysis. New data confirm previous observations associating incremental haemodialysis with favourable outcomes. They also raise the possibility that in selected groups and for short periods, the pursuit of set clearance targets during the early days of dialysis may not necessarily bring additional short-term gains. Summary We argue that, while simpler ways of estimating RRF are being explored, future trials must consider implementing incremental haemodialysis focusing on practical aspects of care in the transitional period; safety monitoring in such regimes should be undertaken using conventional methods. Such an approach is likely to benefit a larger subset of haemodialysis population. Correspondence to Dr Adil M. Hazara, Academic Renal Research, 2nd Floor Alderson House, Hull Royal Infirmary, Anlaby Road, Kingston upon Hull HU3 2JZ, UK. Tel: +44 1482 605260; fax: +44 1482 605256; e-mail: adilhazara@nhs.net Copyright © 2019 Wolters Kluwer Health, Inc. All rights reserved.

Assessing the health of the nephron in acute kidney injury: biomarkers of kidney function and injury Purpose of review Serum creatinine and urine output continue to be the mainstays of diagnosis of acute kidney injury, though both of these measures have significant limitations, especially in acutely hospitalized patients. Biomarkers in both blood and urine have been studied extensively in the research setting and are on the verge of clinical practice to improve diagnosis of AKI. Recent findings Blood and urine biomarkers can be localized to specific areas or functions within the nephron. Biomarkers can help to characterize glomerular or tubular function; glomerular, tubular, or interstitial injury; inflammation; or repair. Further, biomarkers can improve diagnosis of AKI in various clinical settings including acute interstitial nephritis, acute tubular injury, and hepatorenal syndrome, and cardiorenal syndrome. Summary Biomarkers are becoming more prevalent in both research and getting close to clinical use. Both blood and urine biomarkers can help to localize impairment in nephron health by either location or function within the nephron and among various causes of AKI. Correspondence to Chirag R. Parikh, MD, PhD, Director, Division of Nephrology, Department of Medicine, Johns Hopkins University School of Medicine, 1830 E Monument St, Ste 416, Baltimore, MD 21287, USA. Tel: +1 410 955 5268; e-mail: chirag.parikh@jhmi.edu Copyright © 2019 Wolters Kluwer Health, Inc. All rights reserved.

Arterial stiffness in chronic kidney disease: a modifiable cardiovascular risk factor? Purpose of review There is an inverse, graded relationship between worsening chronic kidney disease (CKD) and increasing cardiovascular risk independent of traditional cardiovascular risk factors. Increasing arterial stiffness is a powerful predictor of cardiovascular outcomes in CKD. Developing novel therapeutic strategies to reverse this process is an attractive concept. This review presents the results of a literature survey of the last 18 months to establish if arterial stiffness can be considered a reversible cardiovascular risk factor in patients with CKD. Recent findings Multiple potential therapeutic approaches to reduce arterial stiffness have been proposed and tested. However, arterial stiffness and blood pressure (BP) have a very close bidirectional relationship. Any change in BP will have an effect on arterial stiffness and vice versa. At present, there is no robust evidence to support the notion that arterial stiffness can be considered reversible other than as a direct consequence of reduction in BP. Summary For now, arterial stiffness should be considered an indirectly modifiable cardiovascular risk factor through optimal control of BP. Measures of arterial stiffness should be regarded as research and risk stratification tools rather than a therapeutic target in itself. Correspondence to Charles J. Ferro, Department of Nephrology, Queen Elizabeth Hospital Birmingham, Birmingham B15 2WB, UK. Tel: +44 121 3715839; fax: +44 121 3715858; e-mail: charles.ferro@uhb.nhs.uk Copyright © 2019 Wolters Kluwer Health, Inc. All rights reserved.

Acute kidney injury prediction models: current concepts and future strategies Purpose of review Acute kidney injury (AKI) is a critical condition associated with poor patient outcomes. We aimed to review the current concepts and future strategies regarding AKI risk prediction models. Recent findings Recent studies have shown that AKI occurs frequently in patients with common risk factors and certain medical conditions. Prediction models for AKI risk have been reported in medical fields such as critical care medicine, surgery, nephrotoxic agent exposure, and others. However, practical, generalizable, externally validated, and robust AKI prediction models remain relatively rare. Further efforts to develop AKI prediction models based on comprehensive clinical data, artificial intelligence, improved delivery of care, and novel biomarkers may help improve patient outcomes through precise AKI risk prediction. Summary This brief review provides insights for current concepts for AKI prediction model development. In addition, by overviewing the recent AKI prediction models in various medical fields, future strategies to construct advanced AKI prediction models are suggested. Correspondence to Hajeong Lee, MD, Ph.D., Department of Internal Medicine, Seoul National University Hospital, 101 Daehak-ro, Seoul 03080, Jongno-gu, South Korea. Tel.: +82 2 2072 4905;. e-mail: mdhjlee@gmail.com Copyright © 2019 Wolters Kluwer Health, Inc. All rights reserved.

Exploring old concepts and new paradigms No abstract available