benchmarks that will help countries track their progress over time. Conclusion 18 | ISN Global Kidney Health Atlas | 2019 ISN Global Kidney Health Atlas | 2019 Introduction | 19 Chronic kidney disease (CKD) is an immense public health problem; the already high burden of disease is increasing relentlessly worldwide, and the cost of providing adequate care for all CKD patients is overwhelming in many countries.1-6 Previously known as chronic renal failure, CKD is a condition characterized by a gradual loss of kidney function. Because the kidneys play a critical role in filtering waste and excess fluid from the body, impaired kidney function can have detrimental effects to health. This can also lead to the development of other conditions, such as heart failure or cardiovascular problems. Approximately 10% of the world’s population is living with CKD; however, CKD incidence and prevalence differ significantly across countries and world regions.7,8 Although people of every age and race are affected by CKD, people from disadvantaged populations may be at higher risk for the condition (and associated morbidity and mortality) due to socio-economic factors and limited access to care.7-11 SECTION 1 INTRODUCTION 1.1 CKD Figure 1.1 | Classification of CKD A1 A2 A3 Normal to mildly increased Moderately increased Severely increased 300 mg/g >30 mg/mmol G1 Normal or high >_90 ml/min per 1.73 m2 G2 Mildly decreased 60–89 ml/min per 1.73 m2 G3a Mildly to moderately decreased 45–59 ml/min per 1.73 m2 G3b Moderately to severely decreased 30–44 ml/min per 1.73 m2 G4 Severely decreased 15–29 ml/min per 1.73 m2 G5 Kidney failure 3 months) abnormal kidney function, as measured by a glomerular filtration rate (GFR) consistently below 60 ml/min/1.73m2. CKD is divided into six stages of worsening progression based on GFR (see Figure 1.1).5 End-stage kidney disease (ESKD), or kidney failure, occurs when the estimated GFR is less than 15 ml/min/1.73m2, at which point kidney replacement therapy (KRT) typically is required. Over 90% of people with ESKD in low and lower-middle income countries are not receiving KRT. ISN Global Kidney Health Atlas | 2019 Introduction | 21 financing) and cultural (e.g., public and professional attitudes, legal environment) factors.18 Worldwide, patients are increasingly opting for conservative care as an alternative to KRT;16 however, optimal delivery may not be possible in countries where palliative or end-oflife care is limited by resources.19 Ensuring appropriate treatment for ESKD, whether dialysis, transplantation, or conservative care, is an important public health focus for major stakeholders around the world (i.e., the ISN, governments, patients, and care providers). 1.3.1 KRT KRT involves either dialysis or kidney transplantation. There are two modalities of dialysis: peritoneal dialysis (PD) and hemodialysis (HD). In PD, a catheter is placed into the patient’s abdomen and fluid is added to collect and remove waste from the body. PD is administered either continuously or intermittently. For patients with very low kidney function, continuous PD is recommended.20 Typically, patients perform PD in their own homes. In HD, blood is removed from the body and cleaned by a machine which uses a filter to remove waste and excess fluid. The duration and frequency of HD are important factors that influence treatment quality. A longer treatment time may be advantageous, particularly among those with significant volume overload.21 While standard care practices involve dialysis three times per week, the potential benefits of more frequent treatments are currently being studied.21 During 1.3 Treatment for ESKD Low income countries Lower-middle income countries Upper-middle income countries High income countries Figure 1.2 | The state of KRT need, access, and projections into the future n Number of people needing KRT n Number of people receiving KRT Figure 1.3 | Income-related variability in access to KRT n Access to KRT n No access to KRT Estimated number of people needing and receiving KRT worldwide and by World Bank income groups in 2010 and 2030.7 * Calculated based on Liyanage et al.’s7 projections of future KRT received. Need defined as all patients with ESKD who require KRT (maintenance dialysis or kidney transplant) for survival. Access defined as ESKD patients receiving KRT. Regional variability depicted by World Bank income groups based on 2017 country classification. Available at: https://datahelpdesk.worldbank.org/knowledgebase/articles/906519-world-bank-country-and-lending-groups. 9.7 million 14.5 million* 5.4 million 2.6 million 2010 2030 4% 10% 30% 60% 22 | Introduction ISN Global Kidney Health Atlas | 2019 HD, blood is collected by the machine through one of three types of vascular access: fistula, graft, or catheter. HD can be performed at a hospital, a dialysis center, or a patient’s home. Deciding which modality is appropriate for each patient is a complex process. Often, available resources, expertise, and the patient’s condition (i.e., stability, other health problems), guide the modality choice.22 The decision also may depend on other factors, such as a patient’s education level or desire for independence, wait time for transplantation, and distance to a dialysis center, among others.23 The age of the patient at the time of treatment initiation may also be