Chronic kidney disease in the context of "Kidney failure"

A non-communicable disease (NCD) is a disease that is not transmissible directly from one person to another. NCDs include Parkinson's disease, autoimmune diseases, strokes, heart diseases, cancers, diabetes, chronic kidney disease, osteoarthritis, osteoporosis, Alzheimer's disease, cataracts, and others. NCDs may be chronic or acute. Most are non-infectious, although there are some non-communicable infectious diseases, such as parasitic diseases in which the parasite's life cycle does not include direct host-to-host transmission.

The four main NCDs that are the leading causes of death globally are cardiovascular disease, cancer, chronic respiratory diseases, and diabetes. NCDs account for seven out of the ten leading causes of death worldwide. Figures given for 2019 are 41 million deaths due to NCDs worldwide. Of these 17.9 million were due to cardiovascular disease; 9.3 million due to cancer; 4.1 million to chronic respiratory diseases, and 2.0 million to diabetes. Over 80% of the deaths from these four groups were premature, not reaching the age of 70.

Hypertension, also known as high blood pressure, is a long-term medical condition in which the blood pressure in the arteries is persistently elevated. High blood pressure usually does not cause symptoms itself. It is, however, a major risk factor for stroke, coronary artery disease, heart failure, atrial fibrillation, peripheral arterial disease, vision loss, chronic kidney disease, and dementia. Hypertension is a major cause of premature death worldwide.

High blood pressure is classified as primary (essential) hypertension or secondary hypertension. About 90–95% of cases are primary, defined as high blood pressure due to non-specific lifestyle and genetic factors. Lifestyle factors that increase the risk include excess salt in the diet, excess body weight, smoking, physical inactivity and alcohol use. The remaining 5–10% of cases are categorized as secondary hypertension, defined as high blood pressure due to a clearly identifiable cause, such as chronic kidney disease, narrowing of the kidney arteries, an endocrine disorder, or the use of birth control pills.

Diabetic nephropathy, also known as diabetic kidney disease, is the chronic loss of kidney function occurring in those with diabetes mellitus. Diabetic nephropathy is the leading cause of chronic kidney disease (CKD), and end-stage renal disease (ESRD) globally. The triad of protein leaking into the urine (proteinuria or albuminuria), rising blood pressure with hypertension and then falling renal function is common to many forms of CKD. Protein loss in the urine due to damage of the glomeruli may become massive, and cause a low serum albumin with resulting generalized body swelling (edema) so called nephrotic syndrome. Likewise, the estimated glomerular filtration rate (eGFR) may progressively fall from a normal of over 90 ml/min/1.73m to less than 15, at which point the patient is said to have end-stage renal disease. It usually is slowly progressive over years.

Pathophysiologic abnormalities in diabetic nephropathy usually begin with long-standing poorly controlled blood glucose levels. This is followed by multiple changes in the filtration units of the kidneys, the nephrons. (There are normally about 750,000–1.5 million nephrons in each adult kidney). Initially, there is constriction of the efferent arterioles and dilation of afferent arterioles, with resulting glomerular capillary hypertension and hyperfiltration particularly as nephrons become obsolescent and the adaption of hyperfiltration paradoxically causes further shear stress related damage to the delicate glomerular capillaries, further proteinuria, rising blood pressure and a vicious circle of additional nephron damage and decline in overall renal function. Concurrently, there are changes within the glomerulus itself: these include a thickening of the basement membrane, a widening of the slit membranes of the podocytes, an increase in the number of mesangial cells, and an increase in mesangial matrix. This matrix invades the glomerular capillaries and produces deposits called Kimmelstiel-Wilson nodules. The mesangial cells and matrix can progressively expand and consume the entire glomerulus, shutting off filtration.

Renal functions include maintaining an acid–base balance; regulating fluid balance; regulating sodium, potassium, and other electrolytes; clearing toxins; absorption of glucose, amino acids, and other small molecules; regulation of blood pressure; production of various hormones, such as erythropoietin; and activation of vitamin D.

The kidney has many functions, which a well-functioning kidney realizes by filtering blood in a process known as glomerular filtration. A major measure of kidney function is the glomerular filtration rate (GFR).The glomerular filtration rate is the flow rate of filtered fluid through the kidney. The creatinine clearance rate (C_Cr or CrCl) is the volume of blood plasma that is cleared of creatinine per unit time and is a useful measure for approximating the GFR. Creatinine clearance exceeds GFR due to creatinine secretion, which can be blocked by cimetidine. Both GFR and C_Cr may be accurately calculated by comparative measurements of substances in the blood and urine, or estimated by formulas using just a blood test result (eGFR and eC_Cr). The results of these tests are used to assess the excretory function of the kidneys. Staging of chronic kidney disease is based on categories of GFR as well as albuminuria and cause of kidney disease.

Renal replacement therapy (RRT) is therapy that replaces the normal blood-filtering function of the kidneys. It is used when the kidneys are not working well, which is called kidney failure and includes acute kidney injury and chronic kidney disease. Renal replacement therapy includes dialysis (hemodialysis or peritoneal dialysis), hemofiltration, and hemodiafiltration, which are various ways of filtration of blood with or without machines. Renal replacement therapy also includes kidney transplantation, which is the ultimate form of replacement in that the old kidney is replaced by a donor kidney.

These treatments are not truly cures for kidney disease. In the context of chronic kidney disease, they are more accurately viewed as life-extending treatments, although if chronic kidney disease is managed well with dialysis and a compatible graft is found early and is successfully transplanted, the clinical course can be quite favorable, with life expectancy of many years. Likewise, in certain acute illnesses or trauma resulting in acute kidney injury, a person could very well survive for many years, with relatively good kidney function, before needing intervention again, as long as they had good response to dialysis, they got a kidney transplant fairly quickly if needed, their body did not reject the transplanted kidney, and they had no other significant health problems. Early dialysis (and, if indicated, early renal transplant) in acute kidney failure usually brings more favorable outcomes.