Kidneys: anatomy, location and function (2023)

The kidneys are the body's filtration system. These fist-sized, bean-shaped organs control the body's fluid and electrolyte balance, filter blood, remove waste, and regulate hormones. They produce urine to carry waste products out of the body.

Anatomy

Everyone has two kidneys. The kidneys are located on either side of the spine, with the top of each kidney beginning around rib space 11 or 12. The kidneys are sandwiched between the diaphragm and intestines, closer to the back of the abdomen. Each kidney is about the size of a clenched fist, 10 to 12 centimeters long, 5 to 7 centimeters wide and 3 to 5 centimeters thick.Each kidney is connected to the bladder by a ureter. The ureter carries waste products, urine, to the bladder, where it is stored until it exits the body through the urethra. All of these organs together make up the renal system.

Structure

Each kidney is covered with a thick layer of connective tissue and fat that shapes and protects the organ.The kidneys are nourished byrenal veins, arteries and nerves. About 20% of the body's cardiac output, or the amount of blood the heart pumps per minute, passes through the kidneys when the body is at rest.Blood flows to the kidneys through the renal arteries, which originate from the aorta.

As blood flows through the kidneys, the vessels that carry blood get smaller and smaller until they deliver blood to the nephrons. Each kidney contains about 1.3 million nephrons, which do the kidney's filtering work. Inside each nephron is a microscopic filtering unit made up of an outer capsule, the Bowman's capsule, and a network of tiny capillaries called glomeruli.

As the blood moves through the capillary network, or glomerulus, the larger components are filtered out by tiny finger-like structures, and the remaining blood enters Bowman's capsule. From there, the filtered blood collects in the Bowman's capsule until it is channeled into a tubule system. In the tubules, liquid and dissolved substances diffuse through additional filter layers. Some fluids and solutes are reabsorbed and returned to the body through the renal veins into the vena cava, while others are excreted as waste (urine) through the ureters. The ureters carry urine to the bladder for storage until it is expelled from the body through the urethra.

anatomical variations

In some cases, the kidneys do not form properly during pregnancy, leading to birth defects.

• ektopischer Rand: The kidneys initially form in the pelvis and ascend to their permanent position during fetal development. In some cases, the kidneys are never placed in their final location. This can lead to a blockage in the flow of urine and may require surgery to correct.
• bad turn: Just as the kidneys can never fully move into position during development, they can also never fully move into position. Malrotation can result from the kidneys not moving correctly to their final position during development. This can also lead to blockages that may require surgical correction.
• Horseshoe/Fused Kidney: As the kidneys move into their permanent position during development, they can sometimes fuse together, forming a horseshoe shape. The result is one large kidney mass instead of two separate kidneys. In some cases, there are no symptoms to suggest you have a fused kidney, but in other cases, a range of problems can occur, includingKidney stone problemsoder Urinary drainage.
• Renal Anesia: Occasionally, one or both kidneys may never form. Although failure of both kidneys is fatal, a single kidney usually adapts and enlarges to perform the function of two.

function

The main job of the kidneys is to filter the blood and maintain fluid and electrolyte balance in the body. Together, your kidneys filter all of the blood in your body about 300 times a day. Electrolytes and solutes such as sodium and potassium are regulated in the kidneys and transported to different parts of the body. The blood is filtered several times in the kidneys, which recycles about 99% of the water in the blood and converts the remaining water and any waste products into urine.

In addition to filtering blood and removing waste products, one of the vital functions of the kidney is to maintain the body's fluid volume. Electrolytes like sodium play a role, but so do hormones like antidiuretic hormone (ADH), aldosterone, and atrial natriuretic hormone. Electrolytes and hormones respond to the body's needs to increase or decrease fluid volume to maintain blood pressure and whole-body homeostasis.

Associated Terms

a number ofDiseasesand the conditions can affect the functioning of the kidneys. Some are genetic, others develop as a result of other diseases or lifestyles.

• polycystic kidney disease: This is a genetic form of kidney disease that causes cysts to form in the kidney and can lead to kidney failure.
• Kidney stones: They are small masses made up of salts or minerals that accumulate in the kidneys. They can leave the body on their own or require more invasive removal if they block the flow of urine from the body.
• acute renal kidney: This occurs when the kidneys suddenly stop working. Acute renal failure or acute kidney injury occurs rapidly, with fluid and waste accumulating and causing a cascade of problems in the body.
• chronic kidney disease: This is the result of long-term kidney damage that gradually reduces kidney function. While some loss of function is tolerable, serious problems develop when renal function falls below 25%, and life-threatening complications can occur when function falls below 10-15%.
• Krebs: Several types of cancer can affect the kidneys, includingrenal cell carcinoma. Cancer treatments, like other nephrotoxic drugs, can also affect kidney health.

Proof

There are a number of blood tests, urine tests, and tests that can help a doctor determine how well your kidneys are working.

• blood test: Test yoursGlomerular Filtration Rate (GFR)from a blood draw is the best indicator of the glomerulus' ability to filter blood. Normal GFR rates are 90 to 120 milliliters (mL) per minute.Kidney disease is classified based on the range of these numbers, with a GFR less than 15 mL per minute indicating kidney failure or end-stage kidney disease.Other blood tests that can help measure kidney function include creatinine, blood urea nitrogen, cystatin C, and metabolic panels, which look at electrolyte levels.
• Urine tests: Examination of urine samples can provide information about kidney function. Tests include urinalysis, measuring protein and albumin levels, and osmolarity.
• Pictures: Various tests can help identify kidney function and disease. These tests may include an X-ray, a computed tomography (CT) scan, a nuclear scan of the kidney, or an ultrasound. Scans can be used to determine blood flow through the kidneys or to show cysts, stones, or tumors.

Treatment

With severe kidney damage and loss of function, the body can no longer maintain fluid and electrolyte balance. Toxic levels of waste can cause neurological and/or cardiac problems. While it may help prevent risk factors for kidney disease, such as type 2 diabetes and high blood pressure,renal insufficiencyrequires more intensive treatment. Treatment may include medication or in severe casesDialysis. Dialysis uses an external process to filter the blood instead of the kidneys. Dialysis is usually used until a kidney transplant is possible.

Kidneys can be transplanted from living or deceased donors. Diseased kidneys are sometimes left during the transplant, but in some cases can be removed. The new kidney, usually from a close relative in the case of a living donor, is implanted and connected to the blood vessels and bladder. There are a number of standard surgical risks, plus the possibility that your body will reject the new organ.

If a kidney fails or is donated, it is possible to survive on just one kidney, but there are risks and regular monitoring is required.