The primary purpose of the kidneys is to keep the blood components in the body balanced. This article will review the structure and function, diseases, and strategies to maintain kidney health.
The kidneys are a pair of bean-shaped organs found in the body of all vertebrates. They remove waste products from the body, keep the body’s electrolyte levels balanced and regulate blood pressure.
The kidneys are located on either side of the spine, below the ribs, and behind the stomach. Each kidney’s length is approximately 9 to 12 cm, and the size of each kidney is the size of an adult fist.
The kidneys are one of the essential organs in the body. Before embalming the body, the ancient Egyptians left only the brain and kidneys because they believed that these organs had a higher value.
The function of the kidneys is to purify the blood. They eliminate waste products and control the balance of body fluids and the proper level of electrolytes. All the blood in your body passes through the kidney filters several times a day.
During blood circulation in the body, blood enters the kidneys. Each kidney has about one million tiny filters called nephrons. Blood wastes are excreted and, if needed, salt, water, and minerals are reabsorbed. The filtered blood returns to the bloodstream.
Each kidney weighs 125 to 170 grams in men and 115 to 155 grams in women. Kidney length is also slightly different in men and women. In women, the kidneys’ length is about 9.5 to 11 cm, and in men, 10 to 12 cm.
From the outside to the inside of the kidneys are surrounded by three layers. The outermost layer of connective tissue is called the renal fascia. This layer also covers the adrenal glands (the glands above each kidney). The second layer is the fat capsule around the kidneys, which helps keep the kidneys stable. The third and innermost layer is the kidney capsule. This capsule is composed of complex and robust fibrous structures.
All blood in the human body is filtered by the kidneys several times a day. These organs use about 25 percent of the oxygen absorbed by the lungs to perform this function. Oxygen allows kidney cells to produce chemical energy in ATP (energy carrier molecule) through aerobic respiration. The fluid that filters the blood out of the kidneys is called urine.
Different parts of the kidney
The kidneys are made up of different parts that, together with the bladder, make up the body’s urinary system. In this section, we will introduce the other parts of the kidney:
The nephron is the essential part of the kidney. Nephrons receive blood, metabolize nutrients, and help excrete waste products through filtered blood. Each kidney has about 1 million nephrons, each with its internal structure.
Reasons for importance:
Most people know that the kidneys’ primary function is to excrete waste products and excess fluids from the body. These wastes and extra fluids are excreted in the urine. Urine production involves very complex steps of excretion and reabsorption. This process is necessary to maintain a stable balance of minerals and body composition.
The kidneys regulate blood pressure, produce certain hormones, and maintain the balance of minerals and body fluids.
The kidneys regulate the amount of sodium, potassium, and acid in the body. The kidneys also produce hormones that affect the function of other organs. For example, a hormone produced by the kidneys stimulates the production of red blood cells. Other hormones produced by the kidneys help regulate blood pressure and control calcium metabolism.
- They remove waste products from the body.
- The rest of the drugs are excreted from the body.
- The balance of body fluids.
- They regulate hormones that regulate blood pressure.
- Produces an active form of vitamin D that strengthens bones.
- They control the production of red blood cells.
- Below you can find more information about the kidneys and their vital role in body function.
The primary role of the kidneys is to maintain homeostasis. This means that they manage fluid levels, electrolyte balance, and other factors that keep the body’s internal environment constant and balanced.
The kidneys filter excess water and filter out toxins in the blood. According to the National Institutes of Health (NIH), the kidneys filter about 113 to 144 liters of blood per day and 0.94 to 1.8 liters of urine.
The kidneys are not just a giant sponge to purify the blood. Each system is made up of millions of tiny filters called nephrons.
The nephron has two parts. The glomerulus is the first part of the filter. This filter separates blood cells and large molecules from toxins and liquids. The fluids and toxins that pass through it pass through the renal tubules. The renal tubules collect the minerals the body needs and put them back into the bloodstream, filtering out more toxins.
When filtered, the kidneys produce urine to excrete waste products and toxins. Urine is passed through two tubes called the ureter into the bladder. There, urine leaves the body through the urethra.
Also, the kidneys make hormones for these functions. These hormones help regulate blood pressure, build red blood cells and promote bone health. In general, the kidneys have a wide range of parts, the most important of which are listed in this section:
The kidneys eliminate several wastes and excrete them in the urine. Two main compounds that destroy the kidneys:
Urea, which is produced by the breakdown of proteins.
Uric acid is a substance that is obtained from the breakdown of nucleic acids.
The kidneys return nutrients to the blood during purification to prevent the loss of certain substances and water in the body. They also return other products to the blood to help maintain homeostasis. Reabsorbed products include:
- Amino acid
- Ion chloride
Maintain body pH
In humans, the acceptable pH level is between 7.28 and 7.42. Below this distance, the body enters an acidic state and above this distance, enters an alkaline state.
Outside of this range, proteins and enzymes break down and can no longer function. A drastic change in body pH can be fatal. The kidneys and lungs help maintain a stable pH in the human body. The lungs achieve this by modulating the concentration of carbon dioxide, and the kidneys control pH through two processes:
Reabsorption and regeneration of bicarbonate from urine: Bicarbonate helps neutralize acids. If the pH is tolerable, the kidneys can retain bicarbonate in the urine or release bicarbonate into the blood if the acid level rises.
Removal of hydrogen ions and stable acids: Fixed or non-volatile acids are acids that do not form as a result of carbon dioxide. They are obtained from the incomplete metabolism of carbohydrates, fats, and proteins. These acids include lactic acid, sulfuric acid, and phosphoric acid. By excreting these acids in the urine, the pH level of the blood is controlled.
Regulate blood pressure
The kidneys regulate blood pressure as needed and regulate blood pressure for a more extended period. The kidneys regulate long-term pressure in the arteries by changing the extracellular fluid.
When the volume of blood fluids and blood pressure drops, part of the kidney produces a renin substance and releases it into the bloodstream. This molecule is a vasoconstrictor that raises blood pressure and releases the hormone aldosterone from the adrenal glands.
With the hormone aldosterone’s secretion, the reabsorption of sodium and water from the urine in the kidneys increases, and blood pressure rises. Any factor that changes blood pressure can eventually damage the kidneys. These factors include excessive alcohol consumption, smoking, and obesity.
Along with the liver, the kidneys function to protect our bodies against toxins. A venomous snake bite causes blood to clot. Blood clotting compounds accumulate in the collecting ducts of the kidneys. If left untreated, poisoning can lead to acute kidney damage or permanent kidney failure.
Toxins can be small, medium, or large molecules. Large molecules and most cells are enormous and cannot be transported to the healthy Bowman capsule and remain in the blood. The liver breaks down these molecules into smaller molecules.
Toxins can be any waste. For example, dead cells and by-products of cellular respiration are considered toxins. A wide range of toxins is excreted in the urine.
When excessive toxins damage the kidneys in the body, the damaged nephrons become very absorbent. By looking at larger protein molecules in urine tests such as albumin and red blood cells, it can often be concluded that one or both The kidney is damaged.
Vitamin D activation
The kidneys play an essential role in the activation of vitamin D. Through diet or after sun exposure; vitamin D is transported to the liver, where it is converted to calcidiol.
Healthy kidneys have many receptors for calcidiol that make it an active and usable form of vitamin D called calcitriol. Calcitriol is essential for bone health, calcium absorption, cell growth, muscle function, and immunity.
People with chronic kidney disease sometimes need supplements. Taking an inactive form of vitamin D is of no use to these people because it is the kidneys that convert the inactive form into an active state.
Athletes often drink beverages with added electrolytes when exercising. Sweating destroys essential water-soluble minerals. This loss of electrolytes also occurs during vomiting or diarrhea in the body.
The most common electrolytes in the body are sodium, chloride, potassium, magnesium, phosphate, and bicarbonate. Each of these minerals has several essential roles. Sodium and chloride have a solid tendency to water, and healthy kidneys are very good at removing excess salt from the body.
If you eat a very salty meal, you will probably feel thirsty. Because the kidneys excrete salt components, salt enters the urine with a lot of water. Excess water fills the bladder, and the lack of absorbed water causes the secretion of an anti-diuretic hormone which causes a feeling of thirst.
Minerals have essential functions in our bodies. Therefore, the kidneys need to regulate and maintain their balance. Sodium is critical for intercellular communication and muscle contraction. Sodium and potassium have the opposite effect, and their imbalances in the body can lead to cardiovascular disease.
Phosphate is an essential mineral for bones, teeth, nerves, and muscles. Magnesium is associated with more than 300 different biochemical reactions in the body.
Bicarbonate is a natural alkaline that helps regulate the body’s pH. Carbon dioxide and hydrogen ions are acidic. While we can excrete carbon dioxide when we exhale, other acids must be neutralized or eliminated. Alkaline bicarbonate ions and acidic hydrogen ions form the basis of pH regulation in the body. These ions can be absorbed or reabsorbed in the urine.
Improper kidney care and genetic history of kidney disease can cause a wide range of health problems. Many conditions can cause kidney problems. These include type 1 and type 2 diabetes, high blood pressure, urinary tract obstruction, and inflammation of various parts of the kidney.
Kidney failure is the most severe stage of kidney disease. This happens when the kidneys fail without medical help. People with kidney failure need dialysis or a kidney transplant to survive. People with healthy kidneys can, in most cases, donate a portion of their kidneys to patients in need without getting sick.
Environmental or medical factors may lead to kidney disease. Also, some people are born with functional and structural problems in the kidneys. In this section, we will introduce and review kidney diseases:
Pyelonephritis: Bacteria can infect the kidneys and usually cause back pain and fever. Infection occurs in the pelvis, tubules, and kidney tissue. Bacterial spread due to untreated bladder infection is the most common cause of pyelonephritis.
Kidney stones: The minerals in the urine form crystals that may be large enough to block the urine flow. Kidney stones are one of the most painful kidney diseases. Most kidney stones are excreted spontaneously. But some of them are very large and can cause kidney infection by blocking the urinary tract. In this case, treatment methods such as medication, crusher, and surgery should be used.
Symptoms of kidney disease
Most diseases that affect the kidneys have similar symptoms. If you have symptoms of kidney disease and it comes back, you should see a doctor. Because if left untreated, most kidney diseases can lead to kidney failure. The following are some of the most acute symptoms of these diseases.
Pain in the sides and back: Some kidney diseases such as kidney stones and polycystic kidneys cause pain in the back and sides. Kidney infection can also cause pain in the bones and joints.
Fever: Fever, if present with other symptoms of kidney disease, can indicate a kidney infection.
Frequent and painful urination: The first symptoms of kidney stones are frequent urination (low volume) and pain when urinating.
Blood in the urine: Healthy kidneys do generally not transfer blood cells to the urine when they filter waste products from the blood. But when kidney filters are damaged, they can increase the leakage of blood cells into the urine. The presence of blood in the urine, in addition to kidney disease, can indicate a tumor, kidney stone, or infection.
Discoloration and odor of urine: Discoloration and smell of urine can sign some toxins and abnormal substances in the urine. These changes are often due to kidney stones, kidney infections, and the use of certain medications.
Fatigue, loss of energy, and difficulty concentrating: A severe decrease in kidney function can lead to the accumulation of toxins and impurities in the blood. These problems can cause fatigue, weakness, and difficulty concentrating. Another complication of kidney disease is anemia, which causes weakness and fatigue.
Nausea: Accumulation of waste products and toxins in the body that the kidneys cannot excrete can cause nausea and vomiting.
Swelling of the legs: When the kidneys do not adequately absorb excess body fluids, these fluids can cause swelling in various parts of the body, especially the portions.
Itchy skin: Dry and itchy skin can be a sign of problems with the number of minerals and bones in the body, often with advanced kidney disease. In this disease, the kidneys are no longer able to maintain the balance of minerals and nutrients in the blood.
Muscle cramps: Impaired kidney function causes a disturbance in the body’s volume of fluids and electrolytes. For example, uncontrolled low levels of calcium and phosphorus cause muscle cramps.
Swelling around the eyes: Protein in the urine is the first sign of damage to the kidney filters and causes it to enter the urine. Excretion of protein through urine reduces vascular osmotic pressure and interstitial fluids’ entry into soft tissues such as the eyes and swelling.
The most common causes of kidney damage are:
Misuse of painkillers: Prolonged use of painkillers may lead to chronic analgesic nephritis. These include painkillers such as aspirin, acetaminophen, and nonsteroidal anti-inflammatory drugs (NSAIDs).
Continuous and long-term use of painkillers causes acute renal failure.
Lithium: Doctors prescribe lithium to treat schizophrenia and bipolar disorder. But long-term use of lithium can cause kidney damage. However, with careful medical supervision, the adverse effects of lithium can be prevented.
Chemotherapy agents: The most common type of kidney disease in people with cancer is acute kidney damage. This injury may be caused by severe vomiting and diarrhea, which are common side effects of chemotherapy.
Alcohol: Alcohol alters the kidneys’ ability to purify the blood. It also causes dehydration, and the kidneys have trouble repairing the body’s fluid balance and raising blood pressure, which can prevent the kidneys from functioning properly.
Circulatory problems: Sudden loss or reduction of blood flow to the kidneys can cause kidney failure. Some diseases can cause this problem, including heart attack, liver failure, dehydration, severe burns, allergic reactions, and high blood pressure.
Problems are urinating: When the body cannot urinate, toxins accumulated in the kidneys cause issues. Factors that obstruct the urinary tract include cancers such as prostate, colon, and bladder cancers.
Other factors such as kidney stones, urinary tract, bladder, blood clots in the urinary tract, and damage to the bladder nerves can also cause urinary problems.
Ways to diagnose kidney disease
Early diagnosis and treatment of kidney disease is a way to prevent the disease from progressing and causing kidney failure. Some simple tests can be done to diagnose early kidney disease. Here are some of them:
Blood test: The primary way to diagnose kidney disease is a blood test. This test measures the level of a waste product called creatinine and blood urea. Your doctor will check your blood test results based on your age, weight, and gender to calculate how many milliliters of your kidney waste should be filtered in one minute. Healthy kidneys should generally be able to screen more than 90 ml per minute. If this amount is less as a result of the test, you may have kidney damage.
Urine tests: A variety of urine tests can check kidney function. For example, a urine protein test measures the amount of albumin in your urine by determining the albumin ratio to creatinine (ACR). Excess protein in the urine may indicate that the disease has damaged kidney filtering units. In some cases, the test result may be due to a false positive fever or strenuous exercise that needs to be repeated.
Other tests to diagnose kidney disease
Other tests are sometimes used to assess the extent of kidney damage. These tests may include the following:
Ultrasound, MRI, or CT scan: These tests are used to see the kidneys’ shape and size to check for obstruction, cysts, and tumors. Below is a picture of a polycystic kidney scan.
Treatment of kidney disease
Depending on the cause of the disease, some types of kidney disease can be treated. Often, however, there is no cure for chronic kidney disease.
Treatment for kidney disease usually includes practical measures to control the signs and symptoms, reduce complications, and slow the disease’s progression. If your kidneys are severely damaged, you may need the final stage of treatment for kidney disease. The last step of treatment is described below.
Treat the cause
In this method, the doctor tries to reduce or control the cause of kidney disease. Treatment options vary depending on the cause of the disease.
Treatment of complications
Complications of kidney disease can be controlled to make the condition easier to tolerate. These treatments may include the following:
High blood pressure medications
Medications to treat anemia
Medications to relieve swelling
Medications to protect bones
Low protein diet to minimize waste products in the blood
Treatment of kidney disease in the final stage
If the kidney alone cannot tolerate waste products and excess body fluids and suffers from complete or almost complete kidney failure, the patient is in the so-called last stage of kidney disease. Finally, dialysis or a kidney transplant is needed.
When the kidneys are unable to function, dialysis removes waste products and excess fluid from the patient’s blood.
Kidney transplantation involves placing a healthy kidney through the donor in the patient’s body with surgery. Transplanted kidneys can be received from donors.
How to have healthy kidneys
With the proper lifestyle, our kidneys can always function properly. One of the most important things to keep in mind when it comes to kidney health is keeping your kidneys hydrated or getting enough water. The kidneys need water to function correctly and eliminate toxins from the body.
In this section, suggestions for kidney health and prevention of kidney disease are presented:
Eat a balanced diet: Many kidney problems are caused by 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) recommends the DASH diet to maintain healthy blood pressure.
Get enough exercise: 30 minutes of exercise every day can reduce the risk of high blood pressure and obesity. Both of these effects can affect kidney health.
Drink plenty of water: Consuming fluids, especially water, is essential for kidney health. Consuming about 6 to 8 glasses of water a day can help improve and maintain kidney health.
Drinking 8 glasses of water a day can be effective in maintaining kidney health.
Be careful when taking supplements: Be careful when taking supplements; not all supplements and vitamins are good. If a person takes too many of these drugs, some of them can damage the kidneys. For example, taking too much vitamin C and calcium supplements can cause kidney stones.
Limit salt and some minerals: Limit sodium to a maximum of 2300 mg per day. The required amount of potassium and phosphorus in the body is 2000 and 1000 mg, respectively, and consuming more of them can be harmful to the kidneys.
Avoid smoking: Tobacco smoke clogs blood vessels. Without an adequate blood supply, the kidneys are unable to function normally.
Over-the-counter (OTC) drugs: Over-the-counter medications are not safe just because you do not need them. Overuse of OTC drugs, such as ibuprofen and naproxen, can damage the kidneys.
Get regular screening tests: Anyone with high blood pressure or diabetes should have routine kidney screening to diagnose possible kidney problems as soon as possible.
Get proper sleep and manage your stress: The National Institute of Diabetes and Gastrointestinal Diseases (NIDDK) recommends getting 7 to 8 hours of sleep a night and incorporating stress-reducing activities into your daily routine.
Foods that affect kidney health
Consumption of some foods in the daily diet can effectively maintain the health and function of the kidneys. In this section, we will introduce some of them:
Suitable food for kidney health
Cauliflower and cabbage
Red grapes and apples
garlic and onion