The kidneys are a pair of bean-shaped organs present in all vertebrates. They remove waste products from the body, maintain balanced electrolyte levels, and regulate blood pressure.
The main role of the kidneys is maintaining homeostasis. This means they manage fluid levels, electrolyte balance, and other factors that keep the internal environment of the body consistent and comfortable. They serve a wide range of functions:
The kidneys remove a number of waste products and get rid of them in the urine. Two major compounds that the kidneys remove are:
- urea, which results from the breakdown of proteins
- uric acid from the breakdown of nucleic acids
Re-absorption of Nutrients:
Functions of the kidneys include removing waste, reabsorbing nutrients, and maintaining pH balance. The kidneys reabsorb nutrients from the blood and transport them to where they would best support health. They also reabsorb other products to help maintain homeostasis.
Reabsorbed products include:
- glucose, amino acids, bicarbonate, sodium, water, phosphate, chloride, sodium, magnesium, and potassium ions
In humans, the acceptable pH level is between 7.38 and 7.42. Below this boundary, the body enters a state of acidemia, and above it, alkalemia.
Outside this range, proteins and enzymes break down and can no longer function. In extreme cases, this can be fatal.
The kidneys and lungs help keep a stable pH within the human body. The lungs achieve this by moderating the concentration of carbon dioxide.
Osmolality is a measure of the body’s electrolyte-water balance, or the ratio between fluid and minerals in the body. Dehydration is a primary cause of electrolyte imbalance.
If osmolality rises in the blood plasma, the hypothalamus in the brain responds by passing a message to the pituitary gland. This, in turn, releases antidiuretic hormone (ADH).
In response to ADH, the kidney makes a number of changes, including:
- increasing urine concentration
- increasing water re-absorption
- reopening portions of the collecting duct that water cannot normally enter, allowing water back into the body
- retaining urea in the medulla of the kidney rather than excreting it, as it draws in water
Regulating Blood Pressure:
The kidneys regulate blood pressure when necessary, but they are responsible for slower adjustments.
They adjust long-term pressure in the arteries by causing changes in the fluid outside of cells. The medical term for this fluid is extracellular fluid.
These fluid changes occur after the release of a vasoconstrictor called angiotensin II. Vasoconstrictors are hormones that cause blood vessels to narrow.
They work with other functions to increase the kidneys’ absorption of sodium chloride, or salt. This effectively increases the size of the extracellular fluid compartment and raises blood pressure.
Anything that alters blood pressure can damage the kidneys over time, including excessive alcohol consumption, smoking, and obesity.
Secretion of Active Compounds:
The kidneys release a number of important compounds, including: Erythropoietin, Renin & Calcitriol.
What is chronic kidney disease (CKD)?
Chronic kidney disease includes conditions that damage your kidneys and decrease their ability to keep you healthy by doing the jobs listed. If kidney disease gets worse, wastes can build to high levels in your blood and make you feel sick. You may develop complications like high blood pressure, anemia (low blood count), weak bones, poor nutritional health and nerve damage. Also, kidney disease increases your risk of having heart and blood vessel disease. These problems may happen slowly over a long period of time. Chronic kidney disease may be caused by diabetes, high blood pressure and other disorders. Early detection and treatment can often keep chronic kidney disease from getting worse. When kidney disease progresses, it may eventually lead to kidney failure, which requires dialysis or a kidney transplant to maintain life.
The facts about Chronic Kidney Disease (CKD):
- Early detection can help prevent the progression of kidney disease to kidney failure.
- Heart disease is the major cause of death for all people with CKD.
- Glomerular filtration rate (GFR) is the best estimate of kidney function.
- Hypertension causes CKD and CKD causes hypertension.
- Persistent proteinuria (protein in the urine) means CKD is present.
- High risk groups include those with diabetes, hypertension and family history of kidney failure.
- Two simple tests can detect CKD: blood pressure, urine albumin and serum creatinine.
What causes CKD?
The two main causes of chronic kidney disease are diabetes and high blood pressure, which are responsible for up to two-thirds of the cases. Diabetes happens when your blood sugar is too high, causing damage to many organs in your body, including the kidneys and heart, as well as blood vessels, nerves, and eyes. High blood pressure, or hypertension, occurs when the pressure of your blood against the walls of your blood vessels increases. If uncontrolled, or poorly controlled, high blood pressure can be a leading cause of heart attacks, strokes, and chronic kidney disease. Also, chronic kidney disease can cause high blood pressure.
What are the symptoms of CKD?
Most people may not have any severe symptoms until their kidney disease is advanced. However, you may notice that you:
- feel more tired and have less energy
- have trouble concentrating
- have a poor appetite
- have trouble sleeping
- have muscle cramping at night
- have swollen feet and ankles
- have puffiness around your eyes, especially in the morning
- have dry, itchy skin
- need to urinate more often, especially at night.
Anyone can get chronic kidney disease at any age. However, some people are more likely than others to develop kidney disease. You may have an increased risk for kidney disease if you:
- have diabetes
- have high blood pressure
- have a family history of kidney failure
- are older
- belong to a population group that has a high rate of diabetes or high blood pressure, such as African Americans, Hispanic Americans, Asian, Pacific Islanders, and American Indians.
Maintaining Kidney Health:
The following are suggestions for keeping the kidneys healthy and avoiding kidney disease:
- Eat a balanced diet: Many kidney problems result from high blood pressure and diabetes. As a result, maintaining a healthy diet can prevent several common causes of kidney disease. The National Heart, Lung, and Blood Institute (NHLBI) recommend the DASH diet for maintaining healthy blood pressure.
- Get enough exercise: Exercising for 30 minutes every day can reduce the risk of high blood pressure and obesity, both of which put pressure on kidney health.
- Drink plenty of water: Fluid intake is important, especially water. Around 6 to 8 cups per day can help improve and maintain kidney health.
- Supplements: Be careful when taking supplements, as not all dietary supplements and vitamins are beneficial. Some can harm the kidneys if a person takes too many.
- Salt: Limit sodium intake to a maximum of 2,300 milligrams (mg)of sodium each day.
- Alcohol: Consuming more than one drink per day can harm the kidneys and impair renal function.
- Smoking: Tobacco smoke restricts blood vessels. Without adequate blood supply, the kidneys will not be able to complete their normal work.
- Over-the-counter (OTC) medications: A drug is not harmless simply because a person does not need a prescription to get it. Overusing OTC drugs, such as ibuprofen and naproxen, can damage the kidneys.
- Screening: Anyone with high blood pressure or diabetes should consider regular kidney screening to help spot any possible health issues.
- Diabetes and heart disease: Following the doctor’s recommendations for managing these conditions can help protect the kidneys in the long term.
- Sleep and stress control: The National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) recommend getting 7 to 8 hours of sleep each night and seeking out activities to reduce stress.
Keeping the kidneys in full working order is essential for overall health.*2019 National Kidney Foundation.