Most people have two kidneys, organs that sit in the back of your abdomen. Your kidneys’ primary function is to filter your blood. They also remove waste and balance your body’s fluids. Common kidney conditions include kidney disease, kidney infections and kidney cysts.
The kidneys are two bean-shaped organs that filter your blood. Your kidneys are part of your urinary system.
Your kidneys filter about 200 quarts of fluid every day — enough to fill a large bathtub. During this process, your kidneys remove waste, which leaves your body as urine (pee). Most people pee about two quarts daily. Your body re-uses the other 198 quarts of fluid.
Your kidneys also help balance your body’s fluids (mostly water) and electrolytes. Electrolytes are essential minerals that include sodium and potassium.
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Your kidneys have many important functions. They clean toxins and waste out of your blood. Common waste products include nitrogen waste (urea), muscle waste (creatinine) and acids. They help your body remove these substances. Your kidneys filter about half a cup of blood every minute.
An adrenal gland sits on top of each kidney. It produces hormones, including cortisol, which helps your body respond to stress.
Each kidney contains more than a million filtering units called nephrons. Each nephron consists of:
You can live with just one kidney. Healthcare providers may remove one of your kidneys in a radical nephrectomy.
Someone may have only one kidney if they:
Your kidneys sit just below your ribcage and behind your belly. Typically, one kidney sits on either side of your spine. Your kidneys reside between your intestines and diaphragm. A ureter connects each kidney to your bladder.
Your kidneys are highly complex organs with many parts. The main parts of your kidney anatomy include:
The renal capsule consists of three layers of connective tissue or fat that cover your kidneys. It protects your kidneys from injury, increases their stability and connects your kidneys to surrounding tissues.
The renal artery is a large blood vessel that controls blood flow into your kidneys. For most people at rest, the renal kidneys pump a little over 5 cups (1.2 liters) of blood to your kidneys each minute.
The outer layer of your kidney, where the nephrons (blood-filtering units) begin. The renal cortex also creates the hormone erythropoietin (EPO), which helps make red blood cells in your bone marrow.
The renal medulla is the inner part of your kidney. It contains most of the nephrons with their glomeruli and renal tubules. The renal tubules carry urine to the renal pelvis.
These pyramid-shaped structures transfer urine to the ureters. Dehydration and certain medications — especially nonsteroidal anti-inflammatory drugs (NSAIDs) — may damage your renal papilla.
This funnel-shaped structure collects urine and passes it down two ureters. Urine travels from the ureters to the bladder, where it’s stored.
This vein is the main blood vessel that carries filtered blood out of your kidneys and back to your heart. Each of your kidneys has a renal vein.
Your kidneys are reddish-brown.
Each kidney is about 4 or 5 inches long, around the size of a fist.
The weight of your kidneys varies. Variances may include your height, weight, age, body mass index (BMI) and location.
For men and people assigned male at birth, your right kidney may range from 1/5 to about 1/2 lbs. (79 grams to 223 grams). Your left kidney may range from a little less than 1/5 to a little more than 1/2 lbs. (74 grams to 235 grams). Your kidneys may weigh between the weight of one tennis ball and four tennis balls.
For women and people assigned female at birth, your right kidney may range from a little more than 1/10 to 3/5 lbs. (55 grams to 274 grams). Your left kidney may range from 3/20 to a little less than 3/5 lbs. (67 grams to 261 grams). Your kidneys may weigh between the weight of one tennis ball or five tennis balls.
Your kidneys perform several important functions within your body. Many different disorders can affect them. Common conditions that impact your kidneys include:
Countless other disorders can affect your kidneys. Some of these conditions include:
Most kidney problems don’t have signs in their early stages. As kidney damage progresses, you may notice:
Healthcare providers use several tests to measure kidney function and diagnose kidney problems. Your provider may recommend:
It’s important to have regular checkups and blood and urine tests to measure your kidneys’ health. You can reduce your risk of developing a kidney problem by:
Drinking an appropriate amount of water is good for your kidneys. Water helps your kidneys get rid of toxins and wastes through your pee. It also helps keep your blood vessels healthy, making it easier for blood to deliver necessary nutrients to your kidneys.
It’s also a good idea to drink an appropriate amount of water to help prevent kidney stones and urinary tract infections (UTIs). Kidney stones are less likely to form when you have enough water in your kidneys. You’re less likely to get a UTI when you drink a lot of water because you’ll pee more. Peeing helps flush out the bacteria that cause UTIs.
In general, the color of your pee can reveal if you’re drinking enough water. Your pee should be light yellow or clear if you’re drinking enough water. If you’re dehydrated, your pee will be dark yellow.
On average, men and people assigned male at birth should drink about 13 cups (3 liters) of water each day. On average, women and people assigned female at birth should drink about 9 cups (a little over 2 liters) of water each day.
Yes, it’s possible to drink too much water. Drinking too much water may cause water intoxication or hyponatremia (primary polydipsia). These conditions may cause seizures, coma, mental status changes and death without treatment.
Kidney pain and back pain are similar, and people often confuse them.
Back pain usually occurs in your lower back.
Kidney pain is deeper in your body and higher up your back. You’ll likely feel pain in your sides or your middle- to upper-back area (most often under your ribs, to the right or left of your spine). The pain may progress to other areas, including your abdomen or groin.
Kidney pain results from swelling or blockage of your kidneys or urinary tract. Symptoms include fever, nausea, vomiting or pain when you pee.
Kidney conditions can cause different symptoms in different people. If your kidneys aren’t working correctly, you may notice one or more of the following signs:
You should have your kidney function regularly tested if you have:
A note from Cleveland Clinic
Your kidneys filter your blood and remove waste from your body. Your kidneys also help balance your body’s fluids and electrolytes. Many different conditions may affect your kidneys, so it’s essential to take steps to keep your kidneys healthy. Regular testing is a good idea if you have a high risk for kidney problems.
Last reviewed by a Cleveland Clinic medical professional on 05/17/2022.
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