Kidney Disease

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What is kidney disease?

Kidney disease occurs when the kidneys are damaged and cannot function properly. Numerous conditions and diseases can result in damage to the kidneys, thus affecting their ability to filter waste from the blood while reabsorbing important substances. Generally, kidney disease may present or develop in a few different ways:

  • Acute kidney injury (AKI) is the rapid loss of kidney function. It may be recognised when a person suddenly produces much less urine and/or has a significant increase in the level of waste products in the blood that the kidneys normally filter out. As such AKI is not a specific diagnosis but is the response of the kidneys to a certain bodily insult. The response of the healthcare team is to identify and treat that insult as quickly as possible. AKI is often the result of concurrent illness including sepsis, an immune attack on the kidneys such as a vasculitis or a medication that may alter the effective blood flow to the kidneys or may cause direct damage. It is common in people who present to hospital: about 15-20% of patients with an acute medical illness will have AKI as part of their overall illness. It is also common in patients who are already hospitalised, such as those who are critically ill and in the intensive care unit. If the damage caused by AKI persists, it can eventually progress to chronic kidney disease.
  • Chronic kidney disease (CKD) occurs over time and is usually defined as lasting over 3 months. The most common causes in the UK are diabetes and high blood pressure (hypertension). Approximately 1 in 10 people in the UK have CKD. In some cases CKD is preventable or, if detected early enough, treatable to prevent or delay progression to kidney failure.
  • Nephrotic syndrome is characterised by the loss of too much protein in the urine. It is caused by damage to the glomeruli and can be a primary disorder of the kidney or secondary to an illness or other condition, such as diabetes or cancer. Along with a high amount of protein in the urine, signs and symptoms of nephrotic syndrome include a low amount of albumin in the blood, higher than normal lipid levels in the blood, and swelling (oedema) in the legs, feet, and ankles. The condition may be acute or chronic, and the outcome can vary.
  • Kidney failure, also called end-stage renal disease or ESRD, is the total or near total loss of kidney function and is permanent. Treatment with haemodialysis, peritoneal dialysis or kidney transplantation are the options at this stage of kidney disease that are necessary to sustain life.

Various factors can cause different patterns of injury to the kidneys and can affect kidney function. Some factors affect the functional units, the nephrons, or parts of the nephrons, such as the glomeruli or the tubules. Some factors affect the passage of urine from the kidney while others cause damage to the kidney(s) as a whole.

The most common causes of and main risk factors for kidney disease are:

  • Diabetes: a sustained high level of blood glucose from uncontrolled diabetes can over time damage the nephrons in the kidneys. This risk can be minimised by maintaining good glucose control.
  • High blood pressure (hypertension): can damage blood vessels within the kidneys,and thus can cause CKD. Conversely, having CKD can cause high blood pressure as well and a critical part of CKD management is good blood pressure control.
  • Family history of kidney disease: for example, polycystic kidney disease (PKD) is an inherited disorder in which cysts grow in the kidneys, reducing kidney function over time and eventually leading to kidney failure.

Some other examples of factors affecting the kidneys or patterns of kidney disease include:

  • Glomerulonephritis (The glomerulonephritides are a group of diseases that cause inflammation and damage to the blood filtering units of the kidneys (glomeruli) and are the third most common type of kidney disease. They vary in presentation: they may occur acutely and resolve rapidly; they can present acutely but evolve into a more chronic phase; or they may be chronic causing a gradual decline in renal function. In all forms as blood filtering becomes impaired, water and waste products accumulate in the blood, and blood may appear in the urine (haematuria). In some the haematuria may only be detected on testing of the urine in other forms urine often becomes brown because of broken down blood. Certain body tissues swell with the excess water (a condition called oedema). Outcomes can vary: the condition may go away in a few weeks, permanently reduce kidney function, or progress to kidney failure.
  • Obstruction: the urinary tract can become blocked, or obstructed, from such things as a kidney stone or tumour and, in men, enlargement of the prostate gland. The blockage can lead to infection and injury of the kidney.
  • Autoimmune disease: in autoimmune diseases, the body's immune system mistakenly attacks and damages its own tissue and organs, including the kidneys. Sometimes an autoimmune disorder such as systemic lupus erythematosus or Goodpasture's syndrome can lead to glomerular disease and affect the kidneys.
  • Infections: certain bacteria and viruses can infect the kidneys and cause damage. Urinary tract infections (UTIs) that spread to the kidneys (pyelonephritis) is an example.
  • Immune response: infections in other parts of the body can stimulate an immune response that has an adverse effect on the kidneys. Examples include streptococcal infection of the throat or skin, the skin infection impetigo, an infection inside the heart (endocarditis), or viral infections such as HIV, hepatitis B, or hepatitis C.
  • Congenital defects: defects present at birth, such as those that impede the normal flow of urine.
  • Injury: Direct trauma to the kidneys is an uncommon cause of AKI but if severe can lead to chronic kidney disease.
  • Toxins: some contrast dyes used for imaging procedures and certain medications can have toxic effects on the kidneys.
  • Drugs: use and/or overuse of non-steroidal anti-inflammatory drugs (NSAIDS), such as over-the-counter ibuprofen, and various prescription drugs can damage the kidneys. Use of analgesics (pain killers) has been associated with two different forms of kidney damage: AKI and a type of chronic kidney disease called analgesic nephropathy. Certain antibiotics can be directly toxic to the kidneys if their levels are too high. Some drugs may trigger an immune response by the body that subsequently causes kidney damage (interstitial nephritis see below).
  • Pre-renal azotaemia: any situation in which there is reduced blood flow to the kidneys will prevent them from working properly.  This can occur with severe burns, severe dehydration, or septic shock.
  • Interstitial nephritis: a kidney disorder in which the spaces between the kidney tubules become inflamed and swollen. It may be acute or chronic. Causes include side effects of certain medications, certain autoimmune disorders, and having a low blood potassium level or a high blood level of calcium or uric acid. It is associated with decreased urine output, blood in the urine, and oedema. Usually, this is a short-term condition.
  • Acute tubular necrosis (ATN): ATN is the most common causes of dialysis dependent acute kidney failure and will complicate pre-renal azotaemia if the underlying cause for that condition is not managed adequately. It is caused by a lack of oxygen to the kidney tissues or from damage to the kidneys by toxic substances such as contrast dyes used for x-ray studies and certain medications. In most cases, ATN is reversible.

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