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1 Introduction
Chronic kidney disease (CKD) is marked by long-term and usually irreversible loss of kidney function. It may have severe health outcomes. For people who develop end-stage kidney disease, treatment is expensive and requires intensive health services.
People with CKD are at risk of developing various complications and comorbidities, including cardiovascular diseases, respiratory system infections, bone and muscle problems, and anaemia. These problems can begin at a very early stage, even before CKD is detected, and the risks increase with the severity of CKD.
Many of the factors that increase a person’s risk of developing CKD are common in Australia. With an ageing population and increasing prevalence of some risk factors, the number of Australians at risk of CKD is increasing. Nevertheless, effective prevention of CKD is possible as many of these risk factors are modifiable.
The kidneys
The kidneys are two bean-shaped organs located at the back of the abdomen. Each is about the size of a fist. They act as the body’s filters, controlling the level of water and various chemicals, producing certain essential hormones, and clearing waste products from the blood. The waste products and any excess water are eliminated from the body through the bladder in the form of urine. When the kidneys do not work effectively, the body’s chemical balance may be changed, essential bodily processes may be disrupted, and waste products may build up in the blood. This causes damage to the body’s organs and systems, and may result in a range of serious complications.
How are kidney problems detected?
Initial evidence of kidney damage or reduction in kidney function can be detected through routine blood or urine testing. A blood test might find excess levels of waste products that are normally passed into the urine, or a urine test find blood or substances from the blood, that would normally not leak out of the kidneys. The most common indicators of kidney damage are proteins in the urine (proteinuria or albuminuria), blood in the urine (haematuria) and raised levels of urea or creatinine (a waste product of protein metabolism) in the blood.
Kidney function is measured by the glomerular filtration rate (GFR). The glomeruli are networks of blood vessels in the kidneys where the blood is filtered and waste products are removed. The glomerular filtration rate is a measurement of the amount of blood the kidneys clear of waste products in one minute.
Chronic kidney disease
The US Kidney Disease Outcome Quality Initiative (K/DOQI) has developed a definition and clinical guidelines for chronic kidney disease, which were published by the National Kidney Foundation of America (NKF) in 2002. This definition has been widely accepted by
the kidney community in Australia and around the world, and has been endorsed by Kidney Health Australia (Mathew & Johnson 2005).
According to the K/DOQI definition, the presence of chronic kidney disease should be established based on the occurrence of kidney damage and the level of kidney function, regardless of the specific diagnosis of diseases and conditions causing the damage. To be diagnosed with chronic kidney disease, a person must have evidence of kidney damage and/or reduced kidney function lasting for at least 3 months (Box 1.1).
Box 1.1: Diagnostic criteria for chronic kidney disease In the clinical setting, a patient is diagnosed with CKD if he/she meets either of the following criteria:
1. Kidney damage for 3 months or more, as defined by structural or functional abnormalities of the kidney, with or without decreased GFR, manifest by either: - pathological abnormalities; or - markers of kidney damage, including abnormalities in the composition of the blood or urine, or _abnormalities in imaging tests.
- Glomerular filtration rate (GFR) <60 mL/min/1.73 m 2 for 3 months or more, with or without other_ markers of kidney damage. Source: Adapted from NKF 2002.
Severity of chronic kidney disease
The K/DOQI definition classifies chronic kidney disease into five stages of severity, based on evidence of kidney damage and the degree of kidney function reduction, classified by GFR (Box 1.2). Despite the diversity of causes of CKD, the functional changes and clinical manifestations are quite similar across the spectrum. Although the use of the word ‘stage’ implies progression of disease, it is important to note that treatment can slow, delay or prevent further kidney damage in many cases. The proportion of people with CKD who will progress from one stage to the next, and the rate of this progression, are unknown.
In some people with severe CKD, kidney function is insufficient to sustain life and death will follow in a short period (weeks to a month or two). These people are regarded as having ‘end-stage kidney disease’ (ESKD), and require dialysis or a kidney transplant to survive. People receiving dialysis or living with a kidney transplant are said to have ‘treated ESKD’.
Development and course of chronic kidney disease
CKD is a complex disease. It can be caused by a variety of different diseases and conditions, and in most cases develops over a number of years. It is usually asymptomatic until the very late stages, but can lead to impairment of many different organs and body systems even from the very early stages. End-stage kidney disease requires specialised and expensive treatment.
A brief outline of the course of this disease (Figure 1.1) and its main features are provided below. These are discussed in more detail in the following chapters.
Figure 1.1: The course of chronic kidney disease
Asymptomatic nature of chronic kidney disease
In most cases of CKD, kidney function deteriorates over a period of years, but usually a person with CKD has no specific symptoms until the late stages. Initially the only signs of the disease are abnormal results of blood and urine tests (such as a raised blood urea and creatinine, or protein in the urine). A person can lose up to 85% of kidney function before even feeling sick. For this reason, the diagnosis of CKD is often delayed or missed.
Specialised treatment at end stage
In people with end-stage kidney disease, kidney function is no longer sufficient to sustain life. ESKD is one of the most severe outcomes of chronic kidney disease. Before the 1960s, death resulted very soon after reaching end-stage, but over the last 40 years there have been significant advances in our understanding of this condition and its treatment, especially kidney replacement therapy (dialysis and transplant). Since kidney replacement therapy became available and accessible, the lives of many people with ESKD have been prolonged. However, this treatment is still far from perfect. With kidney replacement therapy, the lives of patients with ESKD can be sustained, but the quality of their lives is much reduced and life expectancy is still shortened. Not all people with ESKD will agree to or be well enough to receive kidney replacement therapy.
Multi-organ impairment
ESKD is not the only health outcome of chronic kidney disease. CKD can affect all the organs and systems in the body. Although it is generally asymptomatic until the later stages, impairments of other organ systems due to poor kidney function occur and can be seen at the early stages, such as cardiovascular diseases, bone problems, anaemia and sleep apnoea (Johnson 2004). CKD has profound impacts on the circulatory system. There is substantial evidence that CKD is an independent risk factor for cardiovascular disease (Go et al. 2004).
Risk factors and determinants CKD
1
Stage
5 ESKD
Kidney replacement therapy
Comorbidities and complications
Uraemia
Death Causal diseases
The risks of damage to the circulatory system, as well as to other organs and systems, increase progressively with worsening kidney function. Many people with CKD do not develop ESKD or die from it directly, but die from complications of CKD, particularly heart disease and respiratory infections.
Prevention and management of chronic kidney disease
There is no cure for chronic kidney disease, but the disease is highly preventable and treatable, and progression can be slowed or stopped.
Although there are many factors that can increase the risk of developing CKD, there is strong evidence that many of these factors are modifiable and preventable. Although smoking reduces kidney function and increases the risk of kidney damage, these risks are diminished once smoking is stopped (Briganti et al. 2002; Pinto-Sietsma et al. 2000). A number of studies have shown that blood pressure lowering is associated with substantial slowing of the rate of decline in kidney function (Kshirsagar et al. 2000). In people with diabetes, tight control of blood sugar levels can retard progression of kidney damage and reduce vascular risk (DCCT 1993).
Once CKD has been diagnosed, appropriate therapeutic intervention has been demonstrated in a high-risk population to reduce the rate of progressive deterioration in kidney function and death by 20–50% (Hoy et al. 2003). For patients with advanced CKD, early referral to a nephrologist for consultation and treatment, and receiving care from a multidisciplinary team, have been found to significantly improve the outcomes of kidney replacement therapy and increase patients’ life span (Curtis et al. 2005; Mendelssohn 2005).
Although CKD has many characteristics that are different from other chronic diseases, its occurrence and development largely interact with the onset and progress of certain of these diseases, such as diabetes and cardiovascular disease. Effective strategies for the prevention and management of CKD not only need to address kidney problems, but also need to tackle the problems of other related diseases and shared risk factors.
Although the burden posed by CKD is substantial, there is no national monitoring system for this disease. In the hope of stimulating discussion on this important topic, a brief outline of a possible national monitoring framework for CKD, including examples of potential indicators, is included in Appendix 3 of this report.
Purpose and structure of this report
This report compiles the latest information on CKD from a variety of data sources, with a focus on the modifiable and preventable risk factors associated with chronic kidney disease and the major causes of end-stage kidney disease in those receiving kidney replacement therapy. The aims of the report are:
- to provide an overview of CKD and its impact on the Australian population and the health care system in Australia;
- to describe the major risk factors for CKD and trends in recent years;
- to examine trends in the incidence, prevalence and major causes of treated end-stage kidney disease; and
- to review the current status of prevention and management of the disease.
References
Briganti EM, Branley P, Chadban SJ et al. 2002. Smoking is associated with renal impairment and proteinuria in the normal population: the AusDiab kidney study. American Journal of Kidney Diseases 40:704–12.
Chadban SJ, Briganti EM, Kerr PG et al. 2003. Prevalence of kidney damage in Australian adults: the AusDiab kidney study. Journal of the American Society of Nephrology 14:S131–8.
Curtis BM, Ravani P, Malberti F et al. 2005. The short- and long-term impact of multi- disciplinary clinics in addition to standard nephrology care on patient outcomes. Nephrology Dialysis Transplantation 20:147–54.
DCCT (Diabetes Control and Complications Trial Research Group) 1993. The effect of intensive treatment of diabetes on the development and progression of long-term complications in insulin-dependent diabetes mellitus. New England Journal of Medicine 329:977–98.
Excell L & McDonald SP 2005. New patients commencing treatment in 2003. In: Excell L & McDonald SP (eds). ANZDATA Registry report 2004. Adelaide; Australia and New Zealand Dialysis and Transplant Registry, 7–14.
Go AS, Chertow GM, Fan D, McCulloch CE & Hsu C 2004. Chronic kidney disease and the risks of death, cardiovascular events, and hospitalization. New England Journal of Medicine 351:13.
Hoy WE, Mathews JD, McCredie DA et al. 1998. The multidimensional nature of renal disease: rate and associations of albuminuria in an Australian Aboriginal community. Kidney International 54:1296–1304.
Hoy WE, Wang Z, Baker PR & Kelly AM 2003. Reduction in natural death and renal failure from a systematic screening and treatment program in an Australian Aboriginal community. Kidney International Suppl. 83:S66–73.
Johnson D 2004. Evidence-based guide to slowing the progression of early renal insufficiency. Internal Medicine Journal 34:50–7.
Mathew T & Johnson D 2005. Measurement of kidney function. Medical Observer, 29 July 2005, 29–31.
Mendelssohn DC 2005. Coping with the CKD epidemic: the promise of multidisciplinary team-based care. Nephrology, Dialysis, Transplantation 20:10–2.
NKF (National Kidney Foundation of America) 2002. K/DOQI clinical practice guidelines for chronic kidney disease: evaluation, classification, and stratification. American Journal of Kidney Disease 39 Suppl. 1:S1–266.
Obrador GT & Pereira BJG 2002. Systemic complications of chronic kidney disease. Pinpointing clinical manifestations and best management. Postgraduate Medicine 111(2):115–22.
Pinto-Sietsma SJ, Mulder J, Janssen WM, Hillege HL, de Zeeuw D & de Jong PE 2000. Smoking is related to albuminuria and abnormal renal function in nondiabetic persons. Annals of Internal Medicine 133:585–91.
