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Although medical schools across the United States have updated their curricula to incorporate active learning techniques, there has been little discussion on the nature of the content presented to students. Here, we share detailed examples of our experience in using original experiments to lay the groundwork for foundational concepts in renal physiology and pathophysiology. We believe that this approach offers distinct advantages over standard case-based teaching by (1) starting with simple concepts, (2) analyzing memorable visuals, (3) increasing graphical literacy, (4) translating observations to "rules," (5) encouraging critical thinking, and (6) providing historical perspective to the study of medicine. Although we developed this content for medical students, we have found that many of these lessons are also appropriate as foundational concepts for residents and fellows and serve as an excellent springboard for increasingly complex discussions of clinical applications of physiology. The use of original experiments for teaching and learning in renal physiology harnesses skills in critical thinking and provides a solid foundation that will help learners with subsequent case-based learning in the preclerkship curriculum and in the clinical arena.

Background Acute kidney injury (AKI) is a sudden episode of kidney damage or failure affecting up to 15% of hospitalized patients and is associated with serious short- and long-term complications, mortality, and health care costs. Current practices to diagnose and stage AKI are variable and do not factor in our improved understanding of the biological and analytical variability of creatinine. In addition, the emergence of biomarkers, for example, cystatin C, insulin-like growth factor binding protein 7, and tissue inhibitor of metalloproteinases 2, and electronic notification tools for earlier detection of AKI, highlights the need for updated recommendations to address these developments. Content This AACC Academy guidance document is intended to provide laboratorians and clinicians up-to-date information regarding current best practices for the laboratory investigation of AKI. Topics covered include: clinical indications for further investigating potential AKI, analytical considerations for creatinine assays, the impact of biological variability on diagnostic thresholds, defining “baseline” creatinine, role of traditional markers (urine sodium, fractional excretion of sodium, fractional excretion of urea, and blood urea-to-creatinine ratio), urinary microscopic examination, new biomarkers, improving AKI-associated test utilization, and the utility of automated AKI alerts. Summary The previous decade brought us a significant number of new studies characterizing the performance of existing and new biomarkers, as well as potential new tools for early detection and notification of AKI. This guidance document is intended to inform clinicians and laboratorians on the best practices for the laboratory investigation of AKI, based on expert recommendations where the preponderance of evidence is available.

The search for a reliable strategy to easily measure kidney function has been likened to the search for the holy grail in nephrology because the interpretation of the measured blood creatinine requires an understanding of the nonlinear and reciprocal relationship between renal function and

As the U.S. health care system changes and technology alters how doctors work and learn, medical schools and their faculty are compelled to modify their curricula and teaching methods. In this article, educational leaders and key faculty describe how the Pathways curriculum was conceived, designed, and implemented at Harvard Medical School. Faculty were committed to the principle that educators should focus on how students learn and their ability to apply what they learn in the evaluation and care of patients. Using the best evidence from the cognitive sciences about adult learning, they made major changes in the pedagogical approach employed in the classroom and clinic. The curriculum was built upon 4 foundational principles: to enhance critical thinking and provide developmentally appropriate content; to ensure both horizontal integration between courses and vertical integration between phases of the curriculum; to engage learners, foster curiosity, and reinforce the importance of student ownership and responsibility for their learning; and to support students' transformation to a professional dedicated to the care of their patients and to their obligations for lifelong, self-directed learning.The practice of medicine is rapidly evolving and will undoubtedly change in multiple ways over the career of a physician. By emphasizing personal responsibility, professionalism, and thinking skills over content transfer, the authors believe this curriculum will prepare students not only for the first day of practice but also for an uncertain future in the biological sciences, health and disease, and the nation's health care system, which they will encounter in the decades to come.

Background Urine albumin-to-creatinine ratio (uACR) is a screening assay for chronic kidney disease (CKD). A value of >30 mg/g is flagged abnormal, but lower ratios have prognostic implications. Thus, to maximize diagnostic utility, urine albumin (uAlb) should be measurable to 3 mg/L to match the lowest creatinine concentration generally utilized (10 mg/dL). Most uAlb assays have lower limits of quantitation (LLOQs) 2- to 4-fold higher. We sought to determine the performance characteristics of a commonly used uAlb assay at 3 mg/L and to evaluate the clinical screening impact of reducing the LLOQ. Methods Urine was serially diluted to assess uAlb linearity and precision for concentrations near the claimed LLOQ (12 mg/L). Samples (n = 30) with uAlb Results The assay was linear to 1.6 mg/L. Interday precision at 3.7 mg/L and 4.3 mg/L was 7.7% and 8.6%, respectively. Minimal bias was observed between labs (y = 1.091x − 0.75; average bias = −0.13 mg/L). Clinical validation demonstrated 501 of 1239 samples (40.4%) had uAlb 10 mg/L, 107 of 499 (21.4%) would have a ratio flagged abnormal at >30 mg/g. Using the numeric value for these samples to 3 mg/L reduced alarm to Conclusions A uAlb LLOQ of 3 mg/L improves screening utility of uACR by simplifying reporting and clinical interpretation when uAlb is low and provides clinical information for prognostic tools developed for people at risk of CKD.

Background Commonly used estimated glomerular filtration rate (eGFR) equations include a Black race modifier (BRM) that was incorporated during equation derivation. Race is a social construct, and a poorly characterized variable that is applied inconsistently in clinical settings. The BRM results in higher eGFR for any creatinine concentration, implying fundamental differences in creatinine production or excretion in Black individuals compared to other populations. Equations without inclusion of the BRM have the potential to detect kidney disease earlier in patients at the greatest risk of chronic kidney disease (CKD), but also has the potential to over-diagnose CKD or impact downstream clinical interventions. The purpose of this study was to use an evidence-based approach to systematically evaluate the literature relevant to the performance of the eGFR equations with and without the BRM and to examine the clinical impact of the use or removal. Content PubMed and Embase databases were searched for studies comparing measured GFR to eGFR in racially diverse adult populations using the Modification of Diet in Renal Disease or the 2009-Chronic Kidney Disease Epidemiology Collaboration-creatinine equations based on standardized creatinine measurements. Additionally, we searched for studies comparing clinical use of eGFR calculated with and without the BRM. Here, 8632 unique publications were identified; an additional 3 studies were added post hoc. In total, 96 studies were subjected to further analysis and 44 studies were used to make a final assessment. Summary There is limited published evidence to support the use of a BRM in eGFR equations.

Fractional excretion of urinary sodium (FENa) is a widely utilized clinical test to evaluate acute kidney injury (AKI). A low FENa (1%) is deemed consistent with prerenal azotemia and inconsistent with acute tubular injury (ATI). Muddy brown granular casts (MBGC) on microscopic examination of urinary sediment (MicrExUrSed) are highly suggestive of ATI. We hypothesized that there is poor concordance between the presence of MBGC and FENa in ATI.We conducted a prospective observational study in patients with AKI seen during inpatient consultation. We extracted patients who underwent assessment of percentage of low power fields (LPFs) with MBGC by MicrExUrSed and concomitant measurement of FENa. Diagnostic concordance between MBGC and FENa and their individual prognostic value were examined.Our cohort included 270 patients, 111 (41%) of whom were women. Median age was 61 years (range 27-92 years), and median serum creatinine was 3.7 mg/dl ( range1.2-22.0 mg/dl). MBGC were found in 49% (133/270). FENa1% (inconsistent with ATI) was found in 50/133 (38%), 38/115 (33%), and 16/45 (36%) of those with0%, ≥10%, and ≥50% LPFs with MBGC, respectively. Concordance between FENa and MBGC for ATI diagnosis was deemed fair (estimatedAbout two of five patients with MBGC identified by MicrExUrSed presented with FENa1%. Presence of MBGC was consistent with ATI, as verified by biopsy, and were predictive of AKD. These data suggest that the sole reliance in low FENa to exclude ATI should be abandoned, and MicrExUrSed should be pursued for AKI diagnosis.

Evaluation of patients with acute kidney injury requires comprehensive assessment that includes a urinalysis, which features both semi-quantitative assessment with a urine dipstick and urine microscopy. This process is labor intensive for clinical laboratories, and availability of excellent automated instruments for urinalysis has prompted utilization and acceptance of this strategy by both by laboratories and clinicians. Recently, however, interest in provider performed microscopy has enjoyed a renaissance thanks to both improved microscopy techniques and the endorsement from social media in nephrology. Here, we present two cases of acute kidney injury in which manual microscopy added valuable information to the automated microscopy.

Race is a social construct that cannot be measured, can be used imprecisely and may contribute to disparities in kidney transplant access for Black patients. At Beth Israel Deaconess Medical Center, we dropped the Black race coefficient in the estimated glomerular filtration rate (eGFR) report in 2017. We conducted a quality improvement project to examine the impact of this change. Before the change, only 26% of our Black patients were listed for preemptive transplant compared to 70% of White patients. Since the change, we found a steady increase in the percentage of Black patients listed before starting dialysis. The average eGFR at listing prior to 2017 was significantly lower in Black patients but after, there was no longer a significant difference. 9 patients "gained" an average of 457 days of wait time directly related to discarding the Black race coefficient. Increased time on the list prior to dialysis initiation allows for evaluation of potential live donors and improves the possibility of a pre-emptive live or deceased donor transplant and allows for a shorter period on dialysis before transplant. In this single center initiative, we demonstrate the benefit of discarding race from the eGFR report for Black patients awaiting kidney transplantation. This article is protected by copyright. All rights reserved.

Potassium disorders are common in patients with kidney disease, particularly in patients with tubular disorders and low glomerular filtration rate. A multidisciplinary group of researchers and clinicians met in October 2018 to identify evidence and address controversies in potassium management. The issues discussed encompassed our latest understanding of the regulation of tubular potassium excretion in health and disease; the relationship of potassium intake to cardiovascular and kidney outcomes, with increasing evidence showing beneficial associations with plant-based diet and data to suggest a paradigm shift from the idea of dietary restriction toward fostering patterns of eating that are associated with better outcomes; the paucity of data on the effect of dietary modification in restoring abnormal serum potassium to the normal range; a novel diagnostic algorithm for hypokalemia that takes into account the ascendency of the clinical context in determining cause, aligning the educational strategy with a practical approach to diagnosis; and therapeutic approaches in managing hyperkalemia when chronic and in the emergency or hospital ward. In sum, we provide here our conference deliberations on potassium homeostasis in health and disease, guidance for evaluation and management of dyskalemias in the context of kidney diseases, and research priorities in each of the above areas.

Diet-related chronic diseases are increasing in prevalence and poised to dominate the future careers of current medical students. While the value of nutritionally-informed care and nutrition-based health interventions is increasingly recognized, nutrition education is inconsistently and often inadequately included in medical school curricula. One obstacle to incorporating nutrition into medical and dental school curricula is the density of existing coursework, with incorporation of new material necessitating removal of other material. One solution is to engage students outside the classroom in immersive education in nutrition and metabolism using health-wearables. We report the Metabolic Health Immersion for Medical Education pilot program, spearheaded and designed by Harvard Medical students centering on use of continuous glucose monitors (CGM). Students reported enjoyment with the study, felt encouraged to improve health behaviors, and shared that the experience enhanced their understanding of nutrition and metabolism, was valuable to their medical education, and would influence their future patient care. This study demonstrates proof-of-principle that metabolic health immersion opportunities for health care trainees provide a means of helping to address the current deficit in medical school nutrition education.

A 69-year-old woman is evaluated for 3 days of muscle cramping, weakness, and fatigue. She reports difficulty walking up stairs. She reports no fever, chills, nausea, or vomiting, and no change in bowel movements. In the past 6 months, she was admitted to hospitals elsewhere three times, for

Key Points Question What is the interobserver reliability among practicing nephrologists when interpreting urine sediment findings? Findings In this diagnostic study, 14 nephrologists provided 1064 interpretations of images of urine sediment findings. Agreement could be classified as slight, fair, moderate, substantial, or almost perfect. The interobserver reliability of urine sediment findings is mostly moderate to substantial but varies widely. Meaning Results of this study suggest that efforts to decrease variability in urine sediment interpretations may help increase the yield of this widely used test in medicine., Importance Urine sediment microscopy is commonly performed during the evaluation of kidney disease. Interobserver reliability of nephrologists’ urine sediment examination has not been well studied. Objective Assess interobserver reliability of the urine sediment examination. Design, Setting, and Participants In this diagnostic test study, urine samples were prospectively collected from a convenience sample of adult patients from an academic hospital in the United States undergoing kidney biopsy from July 11, 2018, to March 20, 2019. Digital images and videos of urine sediment findings were captured using a bright-field microscope. These images and videos along with urine dipstick results were incorporated in online surveys and sent to expert nephrologists at 15 US teaching hospitals. They were asked to identify individual sediment findings and the most likely underlying disease process. Exposures Urine dipstick results and urine sediment images from patients undergoing native kidney biopsy. Main Outcomes and Measures Interobserver reliability of urine sediment microscopy findings estimated by overall percent agreement and Fleiss κ coefficients. Secondary outcomes included concordance of diagnoses suspected by nephrologists with corresponding kidney biopsy results. Results In total, 10 surveys from 10 patients containing 76 study questions on individual features were sent to 21 nephrologists, 14 (67%) of whom completed them all. Their combined 1064 responses were analyzed. Overall percent agreement for casts was an estimated 59% (95% CI, 50%-69%), κ = 0.52 (95% CI, 0.42-0.62). For other sediment findings, overall percent agreement was an estimated 69% (95% CI, 61%-77%), κ = 0.65 (95% CI, 0.56-0.73). The κ estimates ranged from 0.13 (95% CI, 0.10-0.17) for mixed cellular casts to 0.90 (95% CI, 0.87-0.94) for squamous epithelial cells. Conclusions and Relevance In this study, substantial variability occurred in the interpretation of urine sediment findings, even among expert nephrologists. Educational or technological innovations may help improve the urine sediment as a diagnostic tool., This diagnostic study assesses interobserver reliability of nephrologist examination of urine sediment using high-resolution digital images and videos of the urine sediment of patients across the US undergoing kidney biopsy.

Although there have been mounting concerns over the decline in applicants to nephrology training programs, strategies to entice students and trainees to pursue a career in nephrology are lacking. Furthermore, the complex factors that contribute to career decisions and the lag between a positive interaction and a decision to pursue nephrology make such strategies difficult to assess. Nevertheless, it is still important to continue efforts to mentor and inspire. This article offers 10 strategies to help nephrologists share passion for nephrology in the clinical arena. These include the excitement of the dialysis unit, ethical dilemmas, pearls for the bedside, and questions "on the fly."

Nephrology ranks next to last in career choices among US medical school graduates. The American Society of Nephrology established a Workforce Committee to help address this issue. Surveys of US medical students indicate that experiences during kidney pathophysiology courses in the preclerkship years may impact their decision to consider a career in nephrology. In October of 2011, preclinical kidney physiology and pathophysiology course directors at US medical schools were surveyed about teaching methods, curricular content, resources, and institutional support for teaching to identify what worked well and what impairs their teaching efforts. A Listserv of these educators, the American Society of Nephrology Renal Educators Listserv, was used to electronically administer the survey. Course leaders from 62 of 114 (54.4%) surveyed medical schools responded. Most of these educators are nephrologists, but physiologists and other clinicians also lead courses; 60% of course directors noted that lectures are videotaped, resulting in decreased attendance. A range of resources is used: 68% use audience response systems, 16% use the simulation center, and none of the educators indicated use of social media (such as Twitter or Facebook); 50% of respondents receive no remuneration, and 68% receive no full-time equivalent for their efforts. Audience response systems, virtual microscopy, and flash animations were identified as valuable teaching tools. Course directors, during subsequent dialogue on the American Society of Nephrology Renal Educators Listserv, have cited incorporation of case scenarios and integration of clinical exposure during preclinical years as methods that inspired interest. Hopefully, adoption of such approaches will ultimately serve to stimulate interest in nephrology.

Understanding the normal renal physiologic changes that occur during pregnancy to renal blood flow and glomerular filtration helps explain the normal decline in serum creatinine and increase in proteinuria that may occur. Women with chronic kidney disease may not be able to make these normal accommodations and are at greater risk of both maternal and fetal complications during pregnancy. Fetal complications are primarily related to intrauterine growth restriction and prematurity. Maternal risks include decline in renal function, worsening hypertension, and preeclampsia. Importantly, hypertension management differs in pregnancy since the goal is to avoid serious maternal and fetal complications but limit exposure of the fetus to unnecessary medications. The risks are greatest for patients with reduced renal function, poorly controlled kidney disease, and significant proteinuria. When women with reduced renal function consider pregnancy, they must be counseled on the potential risks. Sometimes the best option for women with reduced renal function is to wait until after renal transplantation when stable renal function has been achieved. Though renal transplantation and the requisite immunosuppression bring additional challenges, caregivers should strive to counsel patients carefully about the risks of pregnancy in the context of chronic kidney disease but still serve as an advocate for parenting, if this is the goal.

Immune checkpoint inhibitors (CPIs), monoclonal antibodies that target inhibitory receptors expressed on T cells, represent an emerging class of immunotherapy used in treating solid organ and hematologic malignancies. We describe the clinical and histologic features of 13 patients with CPI-induced acute kidney injury (AKI) who underwent kidney biopsy. Median time from initiation of a CPI to AKI was 91 (range, 21 to 245) days. Pyuria was present in 8 patients, and the median urine protein to creatinine ratio was 0.48 (range, 0.12 to 0.98) g/g. An extra-renal immune-related adverse event occurred prior to the onset of AKI in 7 patients. Median peak serum creatinine was 4.5 (interquartile range, 3.6-7.3) mg/dl with 4 patients requiring hemodialysis. The prevalent pathologic lesion was acute tubulointerstitial nephritis in 12 patients, with 3 having granulomatous features, and one thrombotic microangiopathy. Among the 12 patients with acute tubulointerstitial nephritis, 10 received treatment with glucocorticoids, resulting in complete or partial improvement in renal function in 2 and 7 patients, respectively. However, the two patients with acute tubulointerstitial nephritis not given glucocorticoids had no improvement in renal function. Thus, CPI-induced AKI is a new entity that presents with clinical and histologic features similar to other causes of drug-induced acute tubulointerstitial nephritis, though with a longer latency period. Glucocorticoids appear to be a potentially effective treatment strategy. Hence, AKI due to CPIs may be caused by a unique mechanism of action linked to reprogramming of the immune system, leading to loss of tolerance.

With this issue, CJASN begins a new series of review articles designed to reconnect clinical nephrologists and trainees with the fundamentals of renal physiology and pathophysiology. For many of us, our initial interest in nephrology was the result of fascination with clinical fluid and electrolyte

The glomerulus, the filtering unit of the kidney, is a unique bundle of capillaries lined by delicate fenestrated endothelia, a complex mesh of proteins that serve as the glomerular basement membrane and specialized visceral epithelial cells that form the slit diaphragms between interdigitating foot processes. Taken together, this arrangement allows continuous filtration of the plasma volume. The dynamic physical forces that determine the single nephron glomerular filtration are considered. In addition, new insights into the cellular and molecular components of the glomerular tuft and their contribution to glomerular disorders are explored.

The concept of homeostasis has been inextricably linked to the function of the kidneys for more than a century when it was recognized that the kidneys had the ability to maintain the “internal milieu” and allow organisms the “physiologic freedom” to move into varying environments and take in varying diets and fluids. Early ingenious, albeit rudimentary, experiments unlocked a wealth of secrets on the mechanisms involved in the formation of urine and renal handling of the gamut of electrolytes, as well as that of water, acid, and protein. Recent scientific advances have confirmed these prescient postulates such that the modern clinician is the beneficiary of a rich understanding of the nephron and the kidney’s critical role in homeostasis down to the molecular level. This review summarizes those early achievements and provides a framework and introduction for the new CJASN series on renal physiology.

The proximal tubule of the kidney plays a crucial role in the renal handling of drugs (e.g., diuretics), uremic toxins (e.g., indoxyl sulfate), environmental toxins (e.g., mercury, aristolochic acid), metabolites (e.g., uric acid), dietary compounds, and signaling molecules. This process is dependent on many multispecific transporters of the solute carrier (SLC) superfamily, including organic anion transporter (OAT) and organic cation transporter (OCT) subfamilies, and the ATP-binding cassette (ABC) superfamily. We review the basic physiology of these SLC and ABC transporters, many of which are often called drug transporters. With an emphasis on OAT1 (SLC22A6), the closely related OAT3 (SLC22A8), and OCT2 (SLC22A2), we explore the implications of recent in vitro, in vivo, and clinical data pertinent to the kidney. The analysis of murine knockouts has revealed a key role for these transporters in the renal handling not only of drugs and toxins but also of gut microbiome products, as well as liver-derived phase 1 and phase 2 metabolites, including putative uremic toxins (among other molecules of metabolic and clinical importance). Functional activity of these transporters (and polymorphisms affecting it) plays a key role in drug handling and nephrotoxicity. These transporters may also play a role in remote sensing and signaling, as part of a versatile small molecule communication network operative throughout the body in normal and diseased states, such as AKI and CKD.

Coinfection with hepatitis C (HCV) significantly increases the risk of acute and chronic renal disease in HIV-infected individuals. However, the burden of acute kidney injury (AKI) directly attributable to HIV among HCV-infected individuals and associated risk factors are not well understood. Within a prospective cohort, AKI episodes were identified by a rise in creatinine of 0.5 mg/dL. Incidence of first AKI events was calculated for HIV/HCV coinfected versus HCV monoinfected subjects, and multivariable analyses using Cox proportional hazards were performed to identify predictors of AKI. Throughout the study period, 35% HIV/HCV coinfected and 17% HCV monoinfected subjects developed AKI, with incidence of 8.74/100 person-years and 3.53/100 person-years, respectively (hazard ratio (HR) 2.48; [95% confidence interval (CI) 1.50, 3.74]). In multivariable analysis, HIV coinfection (HR 2.19 [1.33, 3.62]), decompensated cirrhosis (HR 6.64 [3.81, 11.6]), and cocaine use (HR 2.06 [1.15, 3.71]) were independently associated with AKI. HCV genotype, HCV viral load, hazardous drinking, and heroin use were not associated with AKI. Study limitations included potential misclassification bias of HCV-infected individuals as serial HIV antibody testing was not routinely performed after study entry, and inability to adjust for tenofovir use in multivariable analysis. In conclusion, among subjects with HCV infection, decompensated cirrhosis, HIV coinfection, and cocaine use are associated with increased risk of AKI. These findings highlight the importance of preventing and treating cirrhosis, controlling HIV coinfection, and reducing cocaine use in HIV/HCV coinfected persons.