The term dialysis is derived from the Greek words dia, meaning "through," and lysis, meaning "loosening or splitting." It is a form of renal replacement therapy, where the kidney's role of filtration of the blood is supplemented by artificial equipment, which removes excess water, solutes, and toxins. Dialysis ensures the maintenance of homeostasis (a stable internal environment) in people experiencing a rapid loss of kidney function, i.e., acute kidney injury (AKI) or a prolonged, gradual loss that is chronic kidney disease (CKD). It is a measure to tide over acute kidney injury, buy time until a kidney transplant can be carried out, or sustain those ineligible for it.
The incidence of renal replacement therapy (RRT) depends on the incidence and prevalence of conditions causing end-stage renal disease (ESRD), early diagnosis of chronic kidney disease (CKD), and measures to slow the progression to end-stage renal disease (ESRD). Systematic identification of patients with a declining estimated glomerular filtration rate (eGFR), heavy proteinuria, and history of acute kidney injury episodes facilitates planned RRT commencement, thus slowing the rising trend in emergency RRT incidence. All patients likely to end up with ESRD and their caregivers must be adequately prepared physically and psychologically and provided with accessible education about future treatment options. Advanced preparation helps avoid dialysis-associated complications such as a malfunctioning catheter or poorly functioning fistula, causing temporary vascular access insertion culminating in sepsis, thrombosis, bleeding, and accelerated mortality. Patients with educational programs are more likely to choose home-based dialysis therapy with societal benefits, less expenditure, and improved quality of life. These programs should commence no later than stage 4 CKD for the patient to have sufficient time and cognition to make informed choices and implement preparatory measures for RRT.
In 2010, approximately 2.5 million people worldwide received chronic RRT, with high absolute rates in North America and maximum prevalence in Taiwan and Japan. Maintenance of regional and national dialysis registries with details on rates, outcomes, and national dialysis practice patterns helps keep track of the population dependent on RRT. They also include hospital-specific information, safety, and quality reporting and provide resources for clinical research. Opting for dialysis is affected by sociocultural and socioeconomic factors. ESRD is disproportionately higher in African Americans and CKD among the White population. ESRD burden is attributed to diabetes mellitus (45%) and hypertension (30%), besides rarer causes like polycystic kidney disease, obstructive nephropathy, and glomerulonephritis. Women are at higher risk for CKD, while men have a higher risk of ESRD. Race disparities can limit access to health care due to their impact on income or the availability of health insurance. Indigenous people in Australia, New Zealand, the United States, and Canada have high rates of kidney disease, less access to transplantation, and poorer outcomes. There are three broad types of dialysis:
Hemodialysis (HD)
Peritoneal dialysis (PD)
Continuous renal replacement therapy (CRRT)
The dynamics of this particular form of renal replacement therapy vary across countries with longer dialysis sessions and slower blood flow rates in Japan. PD is highly prevalent in Hong Kong and the Jalisco region of Mexico, while Home HD is widely adopted in New Zealand and Australia.
The timing for initiation of dialysis is decided after considering the complications of early initiation (unnecessary exposure to IV lines and invasive procedure with risks of infection) against late initiation, causing avoidable volume, metabolic, and electrolyte complications of AKI. Assigning arbitrary urea nitrogen or creatinine level for dialysis initiation is not advisable due to individual variability in uremia symptom severity and renal function. Despite optimal CKD management, patients progress to needing RRT, especially when their eGFR drops below 20 ml/ min/1.73 m2 or they rapidly deteriorate to ESRD within 12 months. The eGFR at dialysis initiation has steadily increased in recent times. In 1996, in the United States, 13% of incident ESRD patients started RRT at an eGFR of 10 ml/min/1.73 m2 or higher. This increased to 43% in 2010 and dropped to 39% in 2015. Waiting for uremic symptoms to set in before commencing RRT had added risks of the patient being malnourished with increased mortality risk. Asking patients to compare their current eating habits and physical activity levels with those 6 to 12 months back helps avoid the lack of awareness. The concept of a 'healthy start,' with dialysis commencing before the onset of severe uremia symptoms, is associated with prolonged survival. An early start will prepone the need for a change of modality or further procedures without any improvement in the quality of life while adding to healthcare costs. The Renal Physicians Association's (RPA) criteria for identifying dialysis patients with a poor prognosis beyond 75 years of age includes:
Provider's estimation of the likelihood of patient mortality in the next six months
Greatly impaired functional status
High comorbidity score
Severe chronic malnutrition (low serum albumin)
Quality of life also strongly predicts mortality. It provides a comprehensive toolkit to encourage shared decision-making.
Mortality rates among dialysis patients are markedly higher among younger age groups, primarily attributed to cardiovascular (40%) and infectious causes (10%). High cardiovascular mortality in dialysis patients could be related to shared risk factors such as chronic inflammation, significant changes in extracellular volume, dystrophic vascular calcification, and altered cardiovascular dynamics during dialysis. The study of heart and renal protection (SHARP) having dialysis and non-dialysis requiring CKD patients showed a 17% reduction in cardiovascular death and major cardiovascular events with simvastatin-ezetimibe treatment. Cardioprotective strategies such as beta-blockers, aspirin, and renin-angiotensin-aldosterone system inhibitors are recommended in dialysis patients based on their cardiovascular risk profile. Hypertension has a graded association with ESRD risk as it is both a cause and a consequence of CKD. The first three months after dialysis initiation, especially among older patients, has the highest mortality rates. This could be due to risks associated with the commencement of dialysis (central venous catheter placement) and more severe comorbidities causing deterioration of renal function. Effective interprofessional collaboration is needed to improve overall outcomes in patients with ESRD requiring dialysis.
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